Repository: cloudwego/hertz
Pull request #1234 (2024-11-20 09:17:43)

refactor(binding): use internal tagexpr
#### What type of PR is this?
refactor

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feat: A new feature
optimize: A new optimization
fix: A bug fix
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refactor: A code change that neither fixes a bug nor adds a feature
style: Changes that do not affect the meaning of the code (white space, formatting, missing semi-colons, etc)
test: Adding missing tests or correcting existing tests
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- [ ] This PR title match the format: \<type\>(optional scope): \<description\>
- [ ] The description of this PR title is user-oriented and clear enough for others to understand.
- [ ] Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. [User docs repo](https://github.com/cloudwego/cloudwego.github.io)


#### (Optional) Translate the PR title into Chinese.
使用internal的tagexpr实现

#### (Optional) More detailed description for this PR(en: English/zh: Chinese).
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en:

```
* remove unused code in github.com/bytedance/go-tagexpr
* remove personal repos github.com/henrylee2cn/*
```

zh(optional):
```
* 去掉无用的 github.com/bytedance/go-tagexpr 代码
* 去掉个人仓库 github.com/henrylee2cn/*
```

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welkeyever: + @FGYFFFF 一起看看
xiaost: @FGYFFFF @welkeyever 我故意分成了两个commit，第一个只是copy代码，第二个才是修改。这样知道变更了什么。

Patch:
diff --git a/go.mod b/go.mod
index 65cd910..d295031 100644
--- a/go.mod
+++ b/go.mod
@@ -3,12 +3,12 @@ module github.com/cloudwego/hertz
 go 1.17
 
 require (
-	github.com/bytedance/go-tagexpr/v2 v2.9.2
 	github.com/bytedance/gopkg v0.1.0
 	github.com/bytedance/mockey v1.2.12
 	github.com/bytedance/sonic v1.12.0
 	github.com/cloudwego/netpoll v0.6.4
 	github.com/fsnotify/fsnotify v1.5.4
+	github.com/nyaruka/phonenumbers v1.0.55
 	github.com/tidwall/gjson v1.14.4
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 	golang.org/x/sys v0.24.0
@@ -21,11 +21,8 @@ require (
 	github.com/cloudwego/iasm v0.2.0 // indirect
 	github.com/golang/protobuf v1.5.0 // indirect
 	github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1 // indirect
-	github.com/henrylee2cn/ameda v1.4.10 // indirect
-	github.com/henrylee2cn/goutil v0.0.0-20210127050712-89660552f6f8 // indirect
 	github.com/jtolds/gls v4.20.0+incompatible // indirect
 	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
-	github.com/nyaruka/phonenumbers v1.0.55 // indirect
 	github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d // indirect
 	github.com/smartystreets/goconvey v1.6.4 // indirect
 	github.com/tidwall/match v1.1.1 // indirect
diff --git a/go.sum b/go.sum
index 98999c7..7e920d4 100644
--- a/go.sum
+++ b/go.sum
@@ -1,6 +1,3 @@
-github.com/bytedance/go-tagexpr/v2 v2.9.2 h1:QySJaAIQgOEDQBLS3x9BxOWrnhqu5sQ+f6HaZIxD39I=
-github.com/bytedance/go-tagexpr/v2 v2.9.2/go.mod h1:5qsx05dYOiUXOUgnQ7w3Oz8BYs2qtM/bJokdLb79wRM=
-github.com/bytedance/gopkg v0.0.0-20240507064146-197ded923ae3/go.mod h1:FtQG3YbQG9L/91pbKSw787yBQPutC+457AvDW77fgUQ=
 github.com/bytedance/gopkg v0.1.0 h1:aAxB7mm1qms4Wz4sp8e1AtKDOeFLtdqvGiUe7aonRJs=
 github.com/bytedance/gopkg v0.1.0/go.mod h1:FtQG3YbQG9L/91pbKSw787yBQPutC+457AvDW77fgUQ=
 github.com/bytedance/mockey v1.2.12 h1:aeszOmGw8CPX8CRx1DZ/Glzb1yXvhjDh6jdFBNZjsU4=
@@ -14,8 +11,6 @@ github.com/cloudwego/base64x v0.1.4 h1:jwCgWpFanWmN8xoIUHa2rtzmkd5J2plF/dnLS6Xd/
 github.com/cloudwego/base64x v0.1.4/go.mod h1:0zlkT4Wn5C6NdauXdJRhSKRlJvmclQ1hhJgA0rcu/8w=
 github.com/cloudwego/iasm v0.2.0 h1:1KNIy1I1H9hNNFEEH3DVnI4UujN+1zjpuk6gwHLTssg=
 github.com/cloudwego/iasm v0.2.0/go.mod h1:8rXZaNYT2n95jn+zTI1sDr+IgcD2GVs0nlbbQPiEFhY=
-github.com/cloudwego/netpoll v0.6.2 h1:+KdILv5ATJU+222wNNXpHapYaBeRvvL8qhJyhcxRxrQ=
-github.com/cloudwego/netpoll v0.6.2/go.mod h1:kaqvfZ70qd4T2WtIIpCOi5Cxyob8viEpzLhCrTrz3HM=
 github.com/cloudwego/netpoll v0.6.4 h1:z/dA4sOTUQof6zZIO4QNnLBXsDFFFEos9OOGloR6kno=
 github.com/cloudwego/netpoll v0.6.4/go.mod h1:BtM+GjKTdwKoC8IOzD08/+8eEn2gYoiNLipFca6BVXQ=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -30,11 +25,6 @@ github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1 h1:EGx4pi6eqNxGaHF6qqu48+N2wcFQ5qg5FXgOdqsJ5d8=
 github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=
-github.com/henrylee2cn/ameda v1.4.8/go.mod h1:liZulR8DgHxdK+MEwvZIylGnmcjzQ6N6f2PlWe7nEO4=
-github.com/henrylee2cn/ameda v1.4.10 h1:JdvI2Ekq7tapdPsuhrc4CaFiqw6QXFvZIULWJgQyCAk=
-github.com/henrylee2cn/ameda v1.4.10/go.mod h1:liZulR8DgHxdK+MEwvZIylGnmcjzQ6N6f2PlWe7nEO4=
-github.com/henrylee2cn/goutil v0.0.0-20210127050712-89660552f6f8 h1:yE9ULgp02BhYIrO6sdV/FPe0xQM6fNHkVQW2IAymfM0=
-github.com/henrylee2cn/goutil v0.0.0-20210127050712-89660552f6f8/go.mod h1:Nhe/DM3671a5udlv2AdV2ni/MZzgfv2qrPL5nIi3EGQ=
 github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
 github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
 github.com/klauspost/cpuid/v2 v2.0.9 h1:lgaqFMSdTdQYdZ04uHyN2d/eKdOMyi2YLSvlQIBFYa4=
@@ -51,14 +41,11 @@ github.com/smartystreets/goconvey v1.6.4/go.mod h1:syvi0/a8iFYH4r/RixwvyeAJjdLS9
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-github.com/tidwall/gjson v1.9.3/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
 github.com/tidwall/gjson v1.14.4 h1:uo0p8EbA09J7RQaflQ1aBRffTR7xedD2bcIVSYxLnkM=
 github.com/tidwall/gjson v1.14.4/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
 github.com/tidwall/match v1.1.1 h1:+Ho715JplO36QYgwN9PGYNhgZvoUSc9X2c80KVTi+GA=
@@ -92,7 +79,6 @@ google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp0
 google.golang.org/protobuf v1.27.1 h1:SnqbnDw1V7RiZcXPx5MEeqPv2s79L9i7BJUlG/+RurQ=
 google.golang.org/protobuf v1.27.1/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/internal/tagexpr/LICENSE b/internal/tagexpr/LICENSE
new file mode 100644
index 0000000..5d7fd6b
--- /dev/null
+++ b/internal/tagexpr/LICENSE
@@ -0,0 +1,201 @@
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diff --git a/internal/tagexpr/README.md b/internal/tagexpr/README.md
new file mode 100644
index 0000000..b248ac3
--- /dev/null
+++ b/internal/tagexpr/README.md
@@ -0,0 +1,3 @@
+# go-tagexpr
+
+originally from https://github.com/bytedance/go-tagexpr
diff --git a/internal/tagexpr/expr.go b/internal/tagexpr/expr.go
new file mode 100644
index 0000000..776a679
--- /dev/null
+++ b/internal/tagexpr/expr.go
@@ -0,0 +1,297 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"fmt"
+)
+
+type variableKeyType string
+
+const variableKey variableKeyType = "__ENV_KEY__"
+
+// Expr expression
+type Expr struct {
+	expr ExprNode
+}
+
+// parseExpr parses the expression.
+func parseExpr(expr string) (*Expr, error) {
+	e := newGroupExprNode()
+	p := &Expr{
+		expr: e,
+	}
+	s := expr
+	err := p.parseExprNode(&s, e)
+	if err != nil {
+		return nil, err
+	}
+	sortPriority(e)
+	return p, nil
+}
+
+func (p *Expr) parseExprNode(expr *string, e ExprNode) error {
+	trimLeftSpace(expr)
+	if *expr == "" {
+		return nil
+	}
+	operand := p.readSelectorExprNode(expr)
+	if operand == nil {
+		operand = p.readRangeKvExprNode(expr)
+		if operand == nil {
+			var subExprNode *string
+			operand, subExprNode = readGroupExprNode(expr)
+			if operand != nil {
+				err := p.parseExprNode(subExprNode, operand)
+				if err != nil {
+					return err
+				}
+			} else {
+				operand = p.parseOperand(expr)
+			}
+		}
+	}
+	if operand == nil {
+		return fmt.Errorf("syntax error: %q", *expr)
+	}
+	trimLeftSpace(expr)
+	operator := p.parseOperator(expr)
+	if operator == nil {
+		e.SetRightOperand(operand)
+		operand.SetParent(e)
+		return nil
+	}
+	if _, ok := e.(*groupExprNode); ok {
+		operator.SetLeftOperand(operand)
+		operand.SetParent(operator)
+		e.SetRightOperand(operator)
+		operator.SetParent(e)
+	} else {
+		operator.SetParent(e.Parent())
+		operator.Parent().SetRightOperand(operator)
+		operator.SetLeftOperand(e)
+		e.SetParent(operator)
+		e.SetRightOperand(operand)
+		operand.SetParent(e)
+	}
+	return p.parseExprNode(expr, operator)
+}
+
+func (p *Expr) parseOperand(expr *string) (e ExprNode) {
+	for _, fn := range funcList {
+		if e = fn(p, expr); e != nil {
+			return e
+		}
+	}
+	if e = readStringExprNode(expr); e != nil {
+		return e
+	}
+	if e = readDigitalExprNode(expr); e != nil {
+		return e
+	}
+	if e = readBoolExprNode(expr); e != nil {
+		return e
+	}
+	if e = readNilExprNode(expr); e != nil {
+		return e
+	}
+	if e = readVariableExprNode(expr); e != nil {
+		return e
+	}
+	return nil
+}
+
+func (*Expr) parseOperator(expr *string) (e ExprNode) {
+	s := *expr
+	if len(s) < 2 {
+		return nil
+	}
+	defer func() {
+		if e != nil && *expr == s {
+			*expr = (*expr)[2:]
+		}
+	}()
+	a := s[:2]
+	switch a {
+	// case "<<":
+	// case ">>":
+	// case "&^":
+	case "||":
+		return newOrExprNode()
+	case "&&":
+		return newAndExprNode()
+	case "==":
+		return newEqualExprNode()
+	case ">=":
+		return newGreaterEqualExprNode()
+	case "<=":
+		return newLessEqualExprNode()
+	case "!=":
+		return newNotEqualExprNode()
+	}
+	defer func() {
+		if e != nil {
+			*expr = (*expr)[1:]
+		}
+	}()
+	switch a[0] {
+	// case '&':
+	// case '|':
+	// case '^':
+	case '+':
+		return newAdditionExprNode()
+	case '-':
+		return newSubtractionExprNode()
+	case '*':
+		return newMultiplicationExprNode()
+	case '/':
+		return newDivisionExprNode()
+	case '%':
+		return newRemainderExprNode()
+	case '<':
+		return newLessExprNode()
+	case '>':
+		return newGreaterExprNode()
+	}
+	return nil
+}
+
+// run calculates the value of expression.
+func (p *Expr) run(field string, tagExpr *TagExpr) interface{} {
+	return p.expr.Run(context.Background(), field, tagExpr)
+}
+
+func (p *Expr) runWithEnv(field string, tagExpr *TagExpr, env map[string]interface{}) interface{} {
+	ctx := context.WithValue(context.Background(), variableKey, env)
+	return p.expr.Run(ctx, field, tagExpr)
+}
+
+/**
+ * Priority:
+ * () ! bool float64 string nil
+ * * / %
+ * + -
+ * < <= > >=
+ * == !=
+ * &&
+ * ||
+**/
+
+func sortPriority(e ExprNode) {
+	for subSortPriority(e.RightOperand(), false) {
+	}
+}
+
+func subSortPriority(e ExprNode, isLeft bool) bool {
+	if e == nil {
+		return false
+	}
+	leftChanged := subSortPriority(e.LeftOperand(), true)
+	rightChanged := subSortPriority(e.RightOperand(), false)
+	if getPriority(e) > getPriority(e.LeftOperand()) {
+		leftOperandToParent(e, isLeft)
+		return true
+	}
+	return leftChanged || rightChanged
+}
+
+func leftOperandToParent(e ExprNode, isLeft bool) {
+	le := e.LeftOperand()
+	if le == nil {
+		return
+	}
+	p := e.Parent()
+	le.SetParent(p)
+	if p != nil {
+		if isLeft {
+			p.SetLeftOperand(le)
+		} else {
+			p.SetRightOperand(le)
+		}
+	}
+	e.SetParent(le)
+	e.SetLeftOperand(le.RightOperand())
+	le.RightOperand().SetParent(e)
+	le.SetRightOperand(e)
+}
+
+func getPriority(e ExprNode) (i int) {
+	// defer func() {
+	// 	printf("expr:%T %d\n", e, i)
+	// }()
+	switch e.(type) {
+	default: // () ! bool float64 string nil
+		return 7
+	case *multiplicationExprNode, *divisionExprNode, *remainderExprNode: // * / %
+		return 6
+	case *additionExprNode, *subtractionExprNode: // + -
+		return 5
+	case *lessExprNode, *lessEqualExprNode, *greaterExprNode, *greaterEqualExprNode: // < <= > >=
+		return 4
+	case *equalExprNode, *notEqualExprNode: // == !=
+		return 3
+	case *andExprNode: // &&
+		return 2
+	case *orExprNode: // ||
+		return 1
+	}
+}
+
+// ExprNode expression interface
+type ExprNode interface {
+	SetParent(ExprNode)
+	Parent() ExprNode
+	LeftOperand() ExprNode
+	RightOperand() ExprNode
+	SetLeftOperand(ExprNode)
+	SetRightOperand(ExprNode)
+	String() string
+	Run(context.Context, string, *TagExpr) interface{}
+}
+
+// var _ ExprNode = new(exprBackground)
+
+type exprBackground struct {
+	parent       ExprNode
+	leftOperand  ExprNode
+	rightOperand ExprNode
+}
+
+func (eb *exprBackground) SetParent(e ExprNode) {
+	eb.parent = e
+}
+
+func (eb *exprBackground) Parent() ExprNode {
+	return eb.parent
+}
+
+func (eb *exprBackground) LeftOperand() ExprNode {
+	return eb.leftOperand
+}
+
+func (eb *exprBackground) RightOperand() ExprNode {
+	return eb.rightOperand
+}
+
+func (eb *exprBackground) SetLeftOperand(left ExprNode) {
+	eb.leftOperand = left
+}
+
+func (eb *exprBackground) SetRightOperand(right ExprNode) {
+	eb.rightOperand = right
+}
+
+func (*exprBackground) Run(context.Context, string, *TagExpr) interface{} { return nil }
diff --git a/internal/tagexpr/handler.go b/internal/tagexpr/handler.go
new file mode 100644
index 0000000..a64d682
--- /dev/null
+++ b/internal/tagexpr/handler.go
@@ -0,0 +1,148 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import "reflect"
+
+// FieldHandler field handler
+type FieldHandler struct {
+	selector string
+	field    *fieldVM
+	expr     *TagExpr
+}
+
+func newFieldHandler(expr *TagExpr, fieldSelector string, field *fieldVM) *FieldHandler {
+	return &FieldHandler{
+		selector: fieldSelector,
+		field:    field,
+		expr:     expr,
+	}
+}
+
+// StringSelector returns the field selector of string type.
+func (f *FieldHandler) StringSelector() string {
+	return f.selector
+}
+
+// FieldSelector returns the field selector of FieldSelector type.
+func (f *FieldHandler) FieldSelector() FieldSelector {
+	return FieldSelector(f.selector)
+}
+
+// Value returns the field value.
+// NOTE:
+//
+//	If initZero==true, initialize nil pointer to zero value
+func (f *FieldHandler) Value(initZero bool) reflect.Value {
+	return f.field.reflectValueGetter(f.expr.ptr, initZero)
+}
+
+// EvalFuncs returns the tag expression eval functions.
+func (f *FieldHandler) EvalFuncs() map[ExprSelector]func() interface{} {
+	targetTagExpr, _ := f.expr.checkout(f.selector)
+	evals := make(map[ExprSelector]func() interface{}, len(f.field.exprs))
+	for k, v := range f.field.exprs {
+		expr := v
+		exprSelector := ExprSelector(k)
+		evals[exprSelector] = func() interface{} {
+			return expr.run(exprSelector.Name(), targetTagExpr)
+		}
+	}
+	return evals
+}
+
+// StructField returns the field StructField object.
+func (f *FieldHandler) StructField() reflect.StructField {
+	return f.field.structField
+}
+
+// ExprHandler expr handler
+type ExprHandler struct {
+	base       string
+	path       string
+	selector   string
+	expr       *TagExpr
+	targetExpr *TagExpr
+}
+
+func newExprHandler(te, tte *TagExpr, base, es string) *ExprHandler {
+	return &ExprHandler{
+		base:       base,
+		selector:   es,
+		expr:       te,
+		targetExpr: tte,
+	}
+}
+
+// TagExpr returns the *TagExpr.
+func (e *ExprHandler) TagExpr() *TagExpr {
+	return e.expr
+}
+
+// StringSelector returns the expression selector of string type.
+func (e *ExprHandler) StringSelector() string {
+	return e.selector
+}
+
+// ExprSelector returns the expression selector of ExprSelector type.
+func (e *ExprHandler) ExprSelector() ExprSelector {
+	return ExprSelector(e.selector)
+}
+
+// Path returns the path description of the expression.
+func (e *ExprHandler) Path() string {
+	if e.path == "" {
+		if e.targetExpr.path == "" {
+			e.path = e.selector
+		} else {
+			e.path = e.targetExpr.path + FieldSeparator + e.selector
+		}
+	}
+	return e.path
+}
+
+// Eval evaluate the value of the struct tag expression.
+// NOTE:
+//
+//	result types: float64, string, bool, nil
+func (e *ExprHandler) Eval() interface{} {
+	return e.expr.s.exprs[e.selector].run(e.base, e.targetExpr)
+}
+
+// EvalFloat evaluates the value of the struct tag expression.
+// NOTE:
+//
+//	If the expression value type is not float64, return 0.
+func (e *ExprHandler) EvalFloat() float64 {
+	r, _ := e.Eval().(float64)
+	return r
+}
+
+// EvalString evaluates the value of the struct tag expression.
+// NOTE:
+//
+//	If the expression value type is not string, return "".
+func (e *ExprHandler) EvalString() string {
+	r, _ := e.Eval().(string)
+	return r
+}
+
+// EvalBool evaluates the value of the struct tag expression.
+// NOTE:
+//
+//	If the expression value is not 0, '' or nil, return true.
+func (e *ExprHandler) EvalBool() bool {
+	return FakeBool(e.Eval())
+}
diff --git a/internal/tagexpr/selector.go b/internal/tagexpr/selector.go
new file mode 100644
index 0000000..7d9e737
--- /dev/null
+++ b/internal/tagexpr/selector.go
@@ -0,0 +1,112 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"strings"
+)
+
+const (
+	// FieldSeparator in the expression selector,
+	// the separator between field names
+	FieldSeparator = "."
+	// ExprNameSeparator in the expression selector,
+	// the separator of the field name and expression name
+	ExprNameSeparator = "@"
+	// DefaultExprName the default name of single model expression
+	DefaultExprName = ExprNameSeparator
+)
+
+// FieldSelector expression selector
+type FieldSelector string
+
+// Name returns the current field name.
+func (f FieldSelector) Name() string {
+	s := string(f)
+	idx := strings.LastIndex(s, FieldSeparator)
+	if idx == -1 {
+		return s
+	}
+	return s[idx+1:]
+}
+
+// Split returns the path segments and the current field name.
+func (f FieldSelector) Split() (paths []string, name string) {
+	s := string(f)
+	a := strings.Split(s, FieldSeparator)
+	idx := len(a) - 1
+	if idx > 0 {
+		return a[:idx], a[idx]
+	}
+	return nil, s
+}
+
+// Parent returns the parent FieldSelector.
+func (f FieldSelector) Parent() (string, bool) {
+	s := string(f)
+	i := strings.LastIndex(s, FieldSeparator)
+	if i < 0 {
+		return "", false
+	}
+	return s[:i], true
+}
+
+// String returns string type value.
+func (f FieldSelector) String() string {
+	return string(f)
+}
+
+// ExprSelector expression selector
+type ExprSelector string
+
+// Name returns the name of the expression.
+func (e ExprSelector) Name() string {
+	s := string(e)
+	atIdx := strings.LastIndex(s, ExprNameSeparator)
+	if atIdx == -1 {
+		return DefaultExprName
+	}
+	return s[atIdx+1:]
+}
+
+// Field returns the field selector it belongs to.
+func (e ExprSelector) Field() string {
+	s := string(e)
+	idx := strings.LastIndex(s, ExprNameSeparator)
+	if idx != -1 {
+		s = s[:idx]
+	}
+	return s
+}
+
+// ParentField returns the parent field selector it belongs to.
+func (e ExprSelector) ParentField() (string, bool) {
+	return FieldSelector(e.Field()).Parent()
+}
+
+// Split returns the field selector and the expression name.
+func (e ExprSelector) Split() (field FieldSelector, name string) {
+	s := string(e)
+	atIdx := strings.LastIndex(s, ExprNameSeparator)
+	if atIdx == -1 {
+		return FieldSelector(s), DefaultExprName
+	}
+	return FieldSelector(s[:atIdx]), s[atIdx+1:]
+}
+
+// String returns string type value.
+func (e ExprSelector) String() string {
+	return string(e)
+}
diff --git a/internal/tagexpr/spec_func.go b/internal/tagexpr/spec_func.go
new file mode 100644
index 0000000..8e6291d
--- /dev/null
+++ b/internal/tagexpr/spec_func.go
@@ -0,0 +1,342 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"regexp"
+	"strings"
+)
+
+// --------------------------- Custom function ---------------------------
+
+var funcList = map[string]func(p *Expr, expr *string) ExprNode{}
+
+// MustRegFunc registers function expression.
+// NOTE:
+//
+//	example: len($), regexp("\\d") or regexp("\\d",$);
+//	If @force=true, allow to cover the existed same @funcName;
+//	The go number types always are float64;
+//	The go string types always are string;
+//	Panic if there is an error.
+func MustRegFunc(funcName string, fn func(...interface{}) interface{}, force ...bool) {
+	err := RegFunc(funcName, fn, force...)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// RegFunc registers function expression.
+// NOTE:
+//
+//	example: len($), regexp("\\d") or regexp("\\d",$);
+//	If @force=true, allow to cover the existed same @funcName;
+//	The go number types always are float64;
+//	The go string types always are string.
+func RegFunc(funcName string, fn func(...interface{}) interface{}, force ...bool) error {
+	if len(force) == 0 || !force[0] {
+		_, ok := funcList[funcName]
+		if ok {
+			return fmt.Errorf("duplicate registration expression function: %s", funcName)
+		}
+	}
+	funcList[funcName] = newFunc(funcName, fn)
+	return nil
+}
+
+func (p *Expr) parseFuncSign(funcName string, expr *string) (boolOpposite *bool, signOpposite *bool, args []ExprNode, found bool) {
+	prefix := funcName + "("
+	length := len(funcName)
+	last, boolOpposite, signOpposite := getBoolAndSignOpposite(expr)
+	if !strings.HasPrefix(last, prefix) {
+		return
+	}
+	*expr = last[length:]
+	lastStr := *expr
+	subExprNode := readPairedSymbol(expr, '(', ')')
+	if subExprNode == nil {
+		return
+	}
+	*subExprNode = "," + *subExprNode
+	for {
+		if strings.HasPrefix(*subExprNode, ",") {
+			*subExprNode = (*subExprNode)[1:]
+			operand := newGroupExprNode()
+			err := p.parseExprNode(trimLeftSpace(subExprNode), operand)
+			if err != nil {
+				*expr = lastStr
+				return
+			}
+			sortPriority(operand)
+			args = append(args, operand)
+		} else {
+			*expr = lastStr
+			return
+		}
+		trimLeftSpace(subExprNode)
+		if len(*subExprNode) == 0 {
+			found = true
+			return
+		}
+	}
+}
+
+func newFunc(funcName string, fn func(...interface{}) interface{}) func(*Expr, *string) ExprNode {
+	return func(p *Expr, expr *string) ExprNode {
+		boolOpposite, signOpposite, args, found := p.parseFuncSign(funcName, expr)
+		if !found {
+			return nil
+		}
+		return &funcExprNode{
+			fn:           fn,
+			boolOpposite: boolOpposite,
+			signOpposite: signOpposite,
+			args:         args,
+		}
+	}
+}
+
+type funcExprNode struct {
+	exprBackground
+	args         []ExprNode
+	fn           func(...interface{}) interface{}
+	boolOpposite *bool
+	signOpposite *bool
+}
+
+func (f *funcExprNode) String() string {
+	return "func()"
+}
+
+func (f *funcExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	var args []interface{}
+	if n := len(f.args); n > 0 {
+		args = make([]interface{}, n)
+		for k, v := range f.args {
+			args[k] = v.Run(ctx, currField, tagExpr)
+		}
+	}
+	return realValue(f.fn(args...), f.boolOpposite, f.signOpposite)
+}
+
+// --------------------------- Built-in function ---------------------------
+func init() {
+	funcList["regexp"] = readRegexpFuncExprNode
+	funcList["sprintf"] = readSprintfFuncExprNode
+	funcList["range"] = readRangeFuncExprNode
+	// len: Built-in function len, the length of struct field X
+	MustRegFunc("len", func(args ...interface{}) (n interface{}) {
+		if len(args) != 1 {
+			return 0
+		}
+		v := args[0]
+		switch e := v.(type) {
+		case string:
+			return float64(len(e))
+		case float64, bool, nil:
+			return 0
+		}
+		defer func() {
+			if recover() != nil {
+				n = 0
+			}
+		}()
+		return float64(reflect.ValueOf(v).Len())
+	}, true)
+	// mblen: get the length of string field X (character number)
+	MustRegFunc("mblen", func(args ...interface{}) (n interface{}) {
+		if len(args) != 1 {
+			return 0
+		}
+		v := args[0]
+		switch e := v.(type) {
+		case string:
+			return float64(len([]rune(e)))
+		case float64, bool, nil:
+			return 0
+		}
+		defer func() {
+			if recover() != nil {
+				n = 0
+			}
+		}()
+		return float64(reflect.ValueOf(v).Len())
+	}, true)
+
+	// in: Check if the first parameter is one of the enumerated parameters
+	MustRegFunc("in", func(args ...interface{}) interface{} {
+		switch len(args) {
+		case 0:
+			return true
+		case 1:
+			return false
+		default:
+			elem := args[0]
+			set := args[1:]
+			for _, e := range set {
+				if elem == e {
+					return true
+				}
+			}
+			return false
+		}
+	}, true)
+}
+
+type regexpFuncExprNode struct {
+	exprBackground
+	re           *regexp.Regexp
+	boolOpposite bool
+}
+
+func (re *regexpFuncExprNode) String() string {
+	return "regexp()"
+}
+
+func readRegexpFuncExprNode(p *Expr, expr *string) ExprNode {
+	last, boolOpposite, _ := getBoolAndSignOpposite(expr)
+	if !strings.HasPrefix(last, "regexp(") {
+		return nil
+	}
+	*expr = last[6:]
+	lastStr := *expr
+	subExprNode := readPairedSymbol(expr, '(', ')')
+	if subExprNode == nil {
+		return nil
+	}
+	s := readPairedSymbol(trimLeftSpace(subExprNode), '\'', '\'')
+	if s == nil {
+		*expr = lastStr
+		return nil
+	}
+	rege, err := regexp.Compile(*s)
+	if err != nil {
+		*expr = lastStr
+		return nil
+	}
+	operand := newGroupExprNode()
+	trimLeftSpace(subExprNode)
+	if strings.HasPrefix(*subExprNode, ",") {
+		*subExprNode = (*subExprNode)[1:]
+		err = p.parseExprNode(trimLeftSpace(subExprNode), operand)
+		if err != nil {
+			*expr = lastStr
+			return nil
+		}
+	} else {
+		currFieldVal := "$"
+		p.parseExprNode(&currFieldVal, operand)
+	}
+	trimLeftSpace(subExprNode)
+	if *subExprNode != "" {
+		*expr = lastStr
+		return nil
+	}
+	e := &regexpFuncExprNode{
+		re: rege,
+	}
+	if boolOpposite != nil {
+		e.boolOpposite = *boolOpposite
+	}
+	e.SetRightOperand(operand)
+	return e
+}
+
+func (re *regexpFuncExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	param := re.rightOperand.Run(ctx, currField, tagExpr)
+	switch v := param.(type) {
+	case string:
+		bol := re.re.MatchString(v)
+		if re.boolOpposite {
+			return !bol
+		}
+		return bol
+	case float64, bool:
+		return false
+	}
+	v := reflect.ValueOf(param)
+	if v.Kind() == reflect.String {
+		bol := re.re.MatchString(v.String())
+		if re.boolOpposite {
+			return !bol
+		}
+		return bol
+	}
+	return false
+}
+
+type sprintfFuncExprNode struct {
+	exprBackground
+	format string
+	args   []ExprNode
+}
+
+func (se *sprintfFuncExprNode) String() string {
+	return "sprintf()"
+}
+
+func readSprintfFuncExprNode(p *Expr, expr *string) ExprNode {
+	if !strings.HasPrefix(*expr, "sprintf(") {
+		return nil
+	}
+	*expr = (*expr)[7:]
+	lastStr := *expr
+	subExprNode := readPairedSymbol(expr, '(', ')')
+	if subExprNode == nil {
+		return nil
+	}
+	format := readPairedSymbol(trimLeftSpace(subExprNode), '\'', '\'')
+	if format == nil {
+		*expr = lastStr
+		return nil
+	}
+	e := &sprintfFuncExprNode{
+		format: *format,
+	}
+	for {
+		trimLeftSpace(subExprNode)
+		if len(*subExprNode) == 0 {
+			return e
+		}
+		if strings.HasPrefix(*subExprNode, ",") {
+			*subExprNode = (*subExprNode)[1:]
+			operand := newGroupExprNode()
+			err := p.parseExprNode(trimLeftSpace(subExprNode), operand)
+			if err != nil {
+				*expr = lastStr
+				return nil
+			}
+			sortPriority(operand)
+			e.args = append(e.args, operand)
+		} else {
+			*expr = lastStr
+			return nil
+		}
+	}
+}
+
+func (se *sprintfFuncExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	var args []interface{}
+	if n := len(se.args); n > 0 {
+		args = make([]interface{}, n)
+		for i, e := range se.args {
+			args[i] = e.Run(ctx, currField, tagExpr)
+		}
+	}
+	return fmt.Sprintf(se.format, args...)
+}
diff --git a/internal/tagexpr/spec_operand.go b/internal/tagexpr/spec_operand.go
new file mode 100644
index 0000000..b14b055
--- /dev/null
+++ b/internal/tagexpr/spec_operand.go
@@ -0,0 +1,363 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// --------------------------- Operand ---------------------------
+
+type groupExprNode struct {
+	exprBackground
+	boolOpposite *bool
+	signOpposite *bool
+}
+
+func newGroupExprNode() ExprNode { return &groupExprNode{} }
+
+func readGroupExprNode(expr *string) (grp ExprNode, subExprNode *string) {
+	last, boolOpposite, signOpposite := getBoolAndSignOpposite(expr)
+	sptr := readPairedSymbol(&last, '(', ')')
+	if sptr == nil {
+		return nil, nil
+	}
+	*expr = last
+	e := &groupExprNode{boolOpposite: boolOpposite, signOpposite: signOpposite}
+	return e, sptr
+}
+
+func (ge *groupExprNode) String() string {
+	return "()"
+}
+
+func (ge *groupExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	if ge.rightOperand == nil {
+		return nil
+	}
+	return realValue(ge.rightOperand.Run(ctx, currField, tagExpr), ge.boolOpposite, ge.signOpposite)
+}
+
+type boolExprNode struct {
+	exprBackground
+	val bool
+}
+
+func (be *boolExprNode) String() string {
+	return fmt.Sprintf("%v", be.val)
+}
+
+var boolRegexp = regexp.MustCompile(`^!*(true|false)([\)\],\|&!= \t]{1}|$)`)
+
+func readBoolExprNode(expr *string) ExprNode {
+	s := boolRegexp.FindString(*expr)
+	if s == "" {
+		return nil
+	}
+	last := s[len(s)-1]
+	if last != 'e' {
+		s = s[:len(s)-1]
+	}
+	*expr = (*expr)[len(s):]
+	e := &boolExprNode{}
+	if strings.Contains(s, "t") {
+		e.val = (len(s)-4)&1 == 0
+	} else {
+		e.val = (len(s)-5)&1 == 1
+	}
+	return e
+}
+
+func (be *boolExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	return be.val
+}
+
+type stringExprNode struct {
+	exprBackground
+	val interface{}
+}
+
+func (se *stringExprNode) String() string {
+	return fmt.Sprintf("%v", se.val)
+}
+
+func readStringExprNode(expr *string) ExprNode {
+	last, boolOpposite, _ := getBoolAndSignOpposite(expr)
+	sptr := readPairedSymbol(&last, '\'', '\'')
+	if sptr == nil {
+		return nil
+	}
+	*expr = last
+	e := &stringExprNode{val: realValue(*sptr, boolOpposite, nil)}
+	return e
+}
+
+func (se *stringExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	return se.val
+}
+
+type digitalExprNode struct {
+	exprBackground
+	val interface{}
+}
+
+func (de *digitalExprNode) String() string {
+	return fmt.Sprintf("%v", de.val)
+}
+
+var digitalRegexp = regexp.MustCompile(`^[\+\-]?\d+(\.\d+)?([\)\],\+\-\*\/%><\|&!=\^ \t\\]|$)`)
+
+func readDigitalExprNode(expr *string) ExprNode {
+	last, boolOpposite := getOpposite(expr, "!")
+	s := digitalRegexp.FindString(last)
+	if s == "" {
+		return nil
+	}
+	if r := s[len(s)-1]; r < '0' || r > '9' {
+		s = s[:len(s)-1]
+	}
+	*expr = last[len(s):]
+	f64, _ := strconv.ParseFloat(s, 64)
+	return &digitalExprNode{val: realValue(f64, boolOpposite, nil)}
+}
+
+func (de *digitalExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	return de.val
+}
+
+type nilExprNode struct {
+	exprBackground
+	val interface{}
+}
+
+func (ne *nilExprNode) String() string {
+	return "<nil>"
+}
+
+var nilRegexp = regexp.MustCompile(`^nil([\)\],\|&!= \t]{1}|$)`)
+
+func readNilExprNode(expr *string) ExprNode {
+	last, boolOpposite := getOpposite(expr, "!")
+	s := nilRegexp.FindString(last)
+	if s == "" {
+		return nil
+	}
+	*expr = last[3:]
+	return &nilExprNode{val: realValue(nil, boolOpposite, nil)}
+}
+
+func (ne *nilExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	return ne.val
+}
+
+type variableExprNode struct {
+	exprBackground
+	boolOpposite *bool
+	val          string
+}
+
+func (ve *variableExprNode) String() string {
+	return fmt.Sprintf("%v", ve.val)
+}
+
+func (ve *variableExprNode) Run(ctx context.Context, variableName string, _ *TagExpr) interface{} {
+	envObj := ctx.Value(variableKey)
+	if envObj == nil {
+		return nil
+	}
+
+	env := envObj.(map[string]interface{})
+	if len(env) == 0 {
+		return nil
+	}
+
+	if value, ok := env[ve.val]; ok && value != nil {
+		return realValue(value, ve.boolOpposite, nil)
+	} else {
+		return nil
+	}
+}
+
+var variableRegex = regexp.MustCompile(`^[a-zA-Z_][a-zA-Z0-9_]*`)
+
+func readVariableExprNode(expr *string) ExprNode {
+	last, boolOpposite := getOpposite(expr, "!")
+	variable := variableRegex.FindString(last)
+	if variable == "" {
+		return nil
+	}
+
+	*expr = (*expr)[len(*expr)-len(last)+len(variable):]
+
+	return &variableExprNode{
+		val:          variable,
+		boolOpposite: boolOpposite,
+	}
+}
+
+func getBoolAndSignOpposite(expr *string) (last string, boolOpposite *bool, signOpposite *bool) {
+	last, boolOpposite = getOpposite(expr, "!")
+	last = strings.TrimLeft(last, "+")
+	last, signOpposite = getOpposite(&last, "-")
+	last = strings.TrimLeft(last, "+")
+	return
+}
+
+func getOpposite(expr *string, cutset string) (string, *bool) {
+	last := strings.TrimLeft(*expr, cutset)
+	n := len(*expr) - len(last)
+	if n == 0 {
+		return last, nil
+	}
+	bol := n&1 == 1
+	return last, &bol
+}
+
+func toString(i interface{}, enforce bool) (string, bool) {
+	switch vv := i.(type) {
+	case string:
+		return vv, true
+	case nil:
+		return "", false
+	default:
+		rv := dereferenceValue(reflect.ValueOf(i))
+		if rv.Kind() == reflect.String {
+			return rv.String(), true
+		}
+		if enforce {
+			if rv.IsValid() && rv.CanInterface() {
+				return fmt.Sprint(rv.Interface()), true
+			} else {
+				return fmt.Sprint(i), true
+			}
+		}
+	}
+	return "", false
+}
+
+func toFloat64(i interface{}, tryParse bool) (float64, bool) {
+	var v float64
+	ok := true
+	switch t := i.(type) {
+	case float64:
+		v = t
+	case float32:
+		v = float64(t)
+	case int:
+		v = float64(t)
+	case int8:
+		v = float64(t)
+	case int16:
+		v = float64(t)
+	case int32:
+		v = float64(t)
+	case int64:
+		v = float64(t)
+	case uint:
+		v = float64(t)
+	case uint8:
+		v = float64(t)
+	case uint16:
+		v = float64(t)
+	case uint32:
+		v = float64(t)
+	case uint64:
+		v = float64(t)
+	case nil:
+		ok = false
+	default:
+		rv := dereferenceValue(reflect.ValueOf(t))
+		switch rv.Kind() {
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			v = float64(rv.Int())
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			v = float64(rv.Uint())
+		case reflect.Float32, reflect.Float64:
+			v = rv.Float()
+		default:
+			if tryParse {
+				if s, ok := toString(i, false); ok {
+					var err error
+					v, err = strconv.ParseFloat(s, 64)
+					return v, err == nil
+				}
+			}
+			ok = false
+		}
+	}
+	return v, ok
+}
+
+func realValue(v interface{}, boolOpposite *bool, signOpposite *bool) interface{} {
+	if boolOpposite != nil {
+		bol := FakeBool(v)
+		if *boolOpposite {
+			return !bol
+		}
+		return bol
+	}
+	switch t := v.(type) {
+	case float64, string:
+	case float32:
+		v = float64(t)
+	case int:
+		v = float64(t)
+	case int8:
+		v = float64(t)
+	case int16:
+		v = float64(t)
+	case int32:
+		v = float64(t)
+	case int64:
+		v = float64(t)
+	case uint:
+		v = float64(t)
+	case uint8:
+		v = float64(t)
+	case uint16:
+		v = float64(t)
+	case uint32:
+		v = float64(t)
+	case uint64:
+		v = float64(t)
+	case []interface{}:
+		for k, v := range t {
+			t[k] = realValue(v, boolOpposite, signOpposite)
+		}
+	default:
+		rv := dereferenceValue(reflect.ValueOf(v))
+		switch rv.Kind() {
+		case reflect.String:
+			v = rv.String()
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			v = float64(rv.Int())
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+			v = float64(rv.Uint())
+		case reflect.Float32, reflect.Float64:
+			v = rv.Float()
+		}
+	}
+	if signOpposite != nil && *signOpposite {
+		if f, ok := v.(float64); ok {
+			v = -f
+		}
+	}
+	return v
+}
diff --git a/internal/tagexpr/spec_operator.go b/internal/tagexpr/spec_operator.go
new file mode 100644
index 0000000..72c4fc6
--- /dev/null
+++ b/internal/tagexpr/spec_operator.go
@@ -0,0 +1,290 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"math"
+)
+
+// --------------------------- Operator ---------------------------
+
+type additionExprNode struct{ exprBackground }
+
+func (ae *additionExprNode) String() string {
+	return "+"
+}
+
+func newAdditionExprNode() ExprNode { return &additionExprNode{} }
+
+func (ae *additionExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	// positive number or Addition
+	v0 := ae.leftOperand.Run(ctx, currField, tagExpr)
+	v1 := ae.rightOperand.Run(ctx, currField, tagExpr)
+	if s0, ok := toFloat64(v0, false); ok {
+		s1, _ := toFloat64(v1, true)
+		return s0 + s1
+	}
+	if s0, ok := toString(v0, false); ok {
+		s1, _ := toString(v1, true)
+		return s0 + s1
+	}
+	return v0
+}
+
+type multiplicationExprNode struct{ exprBackground }
+
+func (ae *multiplicationExprNode) String() string {
+	return "*"
+}
+
+func newMultiplicationExprNode() ExprNode { return &multiplicationExprNode{} }
+
+func (ae *multiplicationExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0, _ := toFloat64(ae.leftOperand.Run(ctx, currField, tagExpr), true)
+	v1, _ := toFloat64(ae.rightOperand.Run(ctx, currField, tagExpr), true)
+	return v0 * v1
+}
+
+type divisionExprNode struct{ exprBackground }
+
+func (de *divisionExprNode) String() string {
+	return "/"
+}
+
+func newDivisionExprNode() ExprNode { return &divisionExprNode{} }
+
+func (de *divisionExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v1, _ := toFloat64(de.rightOperand.Run(ctx, currField, tagExpr), true)
+	if v1 == 0 {
+		return math.NaN()
+	}
+	v0, _ := toFloat64(de.leftOperand.Run(ctx, currField, tagExpr), true)
+	return v0 / v1
+}
+
+type subtractionExprNode struct{ exprBackground }
+
+func (de *subtractionExprNode) String() string {
+	return "-"
+}
+
+func newSubtractionExprNode() ExprNode { return &subtractionExprNode{} }
+
+func (de *subtractionExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0, _ := toFloat64(de.leftOperand.Run(ctx, currField, tagExpr), true)
+	v1, _ := toFloat64(de.rightOperand.Run(ctx, currField, tagExpr), true)
+	return v0 - v1
+}
+
+type remainderExprNode struct{ exprBackground }
+
+func (re *remainderExprNode) String() string {
+	return "%"
+}
+
+func newRemainderExprNode() ExprNode { return &remainderExprNode{} }
+
+func (re *remainderExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v1, _ := toFloat64(re.rightOperand.Run(ctx, currField, tagExpr), true)
+	if v1 == 0 {
+		return math.NaN()
+	}
+	v0, _ := toFloat64(re.leftOperand.Run(ctx, currField, tagExpr), true)
+	return float64(int64(v0) % int64(v1))
+}
+
+type equalExprNode struct{ exprBackground }
+
+func (ee *equalExprNode) String() string {
+	return "=="
+}
+
+func newEqualExprNode() ExprNode { return &equalExprNode{} }
+
+func (ee *equalExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0 := ee.leftOperand.Run(ctx, currField, tagExpr)
+	v1 := ee.rightOperand.Run(ctx, currField, tagExpr)
+	if v0 == v1 {
+		return true
+	}
+	if s0, ok := toFloat64(v0, false); ok {
+		if s1, ok := toFloat64(v1, true); ok {
+			return s0 == s1
+		}
+	}
+	if s0, ok := toString(v0, false); ok {
+		if s1, ok := toString(v1, true); ok {
+			return s0 == s1
+		}
+		return false
+	}
+	switch r := v0.(type) {
+	case bool:
+		r1, ok := v1.(bool)
+		if ok {
+			return r == r1
+		}
+	case nil:
+		return v1 == nil
+	}
+	return false
+}
+
+type notEqualExprNode struct{ equalExprNode }
+
+func (ne *notEqualExprNode) String() string {
+	return "!="
+}
+
+func newNotEqualExprNode() ExprNode { return &notEqualExprNode{} }
+
+func (ne *notEqualExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	return !ne.equalExprNode.Run(ctx, currField, tagExpr).(bool)
+}
+
+type greaterExprNode struct{ exprBackground }
+
+func (ge *greaterExprNode) String() string {
+	return ">"
+}
+
+func newGreaterExprNode() ExprNode { return &greaterExprNode{} }
+
+func (ge *greaterExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0 := ge.leftOperand.Run(ctx, currField, tagExpr)
+	v1 := ge.rightOperand.Run(ctx, currField, tagExpr)
+	if s0, ok := toFloat64(v0, false); ok {
+		if s1, ok := toFloat64(v1, true); ok {
+			return s0 > s1
+		}
+	}
+	if s0, ok := toString(v0, false); ok {
+		if s1, ok := toString(v1, true); ok {
+			return s0 > s1
+		}
+		return false
+	}
+	return false
+}
+
+type greaterEqualExprNode struct{ exprBackground }
+
+func (ge *greaterEqualExprNode) String() string {
+	return ">="
+}
+
+func newGreaterEqualExprNode() ExprNode { return &greaterEqualExprNode{} }
+
+func (ge *greaterEqualExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0 := ge.leftOperand.Run(ctx, currField, tagExpr)
+	v1 := ge.rightOperand.Run(ctx, currField, tagExpr)
+	if s0, ok := toFloat64(v0, false); ok {
+		if s1, ok := toFloat64(v1, true); ok {
+			return s0 >= s1
+		}
+	}
+	if s0, ok := toString(v0, false); ok {
+		if s1, ok := toString(v1, true); ok {
+			return s0 >= s1
+		}
+		return false
+	}
+	return false
+}
+
+type lessExprNode struct{ exprBackground }
+
+func (le *lessExprNode) String() string {
+	return "<"
+}
+
+func newLessExprNode() ExprNode { return &lessExprNode{} }
+
+func (le *lessExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0 := le.leftOperand.Run(ctx, currField, tagExpr)
+	v1 := le.rightOperand.Run(ctx, currField, tagExpr)
+	if s0, ok := toFloat64(v0, false); ok {
+		if s1, ok := toFloat64(v1, true); ok {
+			return s0 < s1
+		}
+	}
+	if s0, ok := toString(v0, false); ok {
+		if s1, ok := toString(v1, true); ok {
+			return s0 < s1
+		}
+		return false
+	}
+	return false
+}
+
+type lessEqualExprNode struct{ exprBackground }
+
+func (le *lessEqualExprNode) String() string {
+	return "<="
+}
+
+func newLessEqualExprNode() ExprNode { return &lessEqualExprNode{} }
+
+func (le *lessEqualExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	v0 := le.leftOperand.Run(ctx, currField, tagExpr)
+	v1 := le.rightOperand.Run(ctx, currField, tagExpr)
+	if s0, ok := toFloat64(v0, false); ok {
+		if s1, ok := toFloat64(v1, true); ok {
+			return s0 <= s1
+		}
+	}
+	if s0, ok := toString(v0, false); ok {
+		if s1, ok := toString(v1, true); ok {
+			return s0 <= s1
+		}
+		return false
+	}
+	return false
+}
+
+type andExprNode struct{ exprBackground }
+
+func (ae *andExprNode) String() string {
+	return "&&"
+}
+
+func newAndExprNode() ExprNode { return &andExprNode{} }
+
+func (ae *andExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	for _, e := range [2]ExprNode{ae.leftOperand, ae.rightOperand} {
+		if !FakeBool(e.Run(ctx, currField, tagExpr)) {
+			return false
+		}
+	}
+	return true
+}
+
+type orExprNode struct{ exprBackground }
+
+func (oe *orExprNode) String() string {
+	return "||"
+}
+
+func newOrExprNode() ExprNode { return &orExprNode{} }
+
+func (oe *orExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	for _, e := range [2]ExprNode{oe.leftOperand, oe.rightOperand} {
+		if FakeBool(e.Run(ctx, currField, tagExpr)) {
+			return true
+		}
+	}
+	return false
+}
diff --git a/internal/tagexpr/spec_range.go b/internal/tagexpr/spec_range.go
new file mode 100644
index 0000000..dcb8872
--- /dev/null
+++ b/internal/tagexpr/spec_range.go
@@ -0,0 +1,164 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"reflect"
+	"regexp"
+)
+
+type rangeCtxKey string
+
+const (
+	rangeKey   rangeCtxKey = "#k"
+	rangeValue rangeCtxKey = "#v"
+	rangeLen   rangeCtxKey = "##"
+)
+
+type rangeKvExprNode struct {
+	exprBackground
+	ctxKey       rangeCtxKey
+	boolOpposite *bool
+	signOpposite *bool
+}
+
+func (re *rangeKvExprNode) String() string {
+	return string(re.ctxKey)
+}
+
+func (p *Expr) readRangeKvExprNode(expr *string) ExprNode {
+	name, boolOpposite, signOpposite, found := findRangeKv(expr)
+	if !found {
+		return nil
+	}
+	operand := &rangeKvExprNode{
+		ctxKey:       rangeCtxKey(name),
+		boolOpposite: boolOpposite,
+		signOpposite: signOpposite,
+	}
+	// fmt.Printf("operand: %#v\n", operand)
+	return operand
+}
+
+var rangeKvRegexp = regexp.MustCompile(`^([\!\+\-]*)(#[kv#])([\)\[\],\+\-\*\/%><\|&!=\^ \t\\]|$)`)
+
+func findRangeKv(expr *string) (name string, boolOpposite, signOpposite *bool, found bool) {
+	raw := *expr
+	a := rangeKvRegexp.FindAllStringSubmatch(raw, -1)
+	if len(a) != 1 {
+		return
+	}
+	r := a[0]
+	name = r[2]
+	*expr = (*expr)[len(a[0][0])-len(r[3]):]
+	prefix := r[1]
+	if len(prefix) == 0 {
+		found = true
+		return
+	}
+	_, boolOpposite, signOpposite = getBoolAndSignOpposite(&prefix)
+	found = true
+	return
+}
+
+func (re *rangeKvExprNode) Run(ctx context.Context, _ string, _ *TagExpr) interface{} {
+	var v interface{}
+	switch val := ctx.Value(re.ctxKey).(type) {
+	case reflect.Value:
+		if !val.IsValid() || !val.CanInterface() {
+			return nil
+		}
+		v = val.Interface()
+	default:
+		v = val
+	}
+	return realValue(v, re.boolOpposite, re.signOpposite)
+}
+
+type rangeFuncExprNode struct {
+	exprBackground
+	object       ExprNode
+	elemExprNode ExprNode
+	boolOpposite *bool
+	signOpposite *bool
+}
+
+func (e *rangeFuncExprNode) String() string {
+	return "range()"
+}
+
+// range($, gt($v,10))
+// range($, $v>10)
+func readRangeFuncExprNode(p *Expr, expr *string) ExprNode {
+	boolOpposite, signOpposite, args, found := p.parseFuncSign("range", expr)
+	if !found {
+		return nil
+	}
+	if len(args) != 2 {
+		return nil
+	}
+	return &rangeFuncExprNode{
+		boolOpposite: boolOpposite,
+		signOpposite: signOpposite,
+		object:       args[0],
+		elemExprNode: args[1],
+	}
+}
+
+func (e *rangeFuncExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	var r []interface{}
+	obj := e.object.Run(ctx, currField, tagExpr)
+	// fmt.Printf("%v\n", obj)
+	objval := reflect.ValueOf(obj)
+	switch objval.Kind() {
+	case reflect.Array, reflect.Slice:
+		count := objval.Len()
+		r = make([]interface{}, count)
+		ctx = context.WithValue(ctx, rangeLen, count)
+		for i := 0; i < count; i++ {
+			// fmt.Printf("%#v,  (%v)\n", e.elemExprNode, objval.Index(i))
+			r[i] = realValue(e.elemExprNode.Run(
+				context.WithValue(
+					context.WithValue(
+						ctx,
+						rangeKey, i,
+					),
+					rangeValue, objval.Index(i),
+				),
+				currField, tagExpr,
+			), e.boolOpposite, e.signOpposite)
+		}
+	case reflect.Map:
+		keys := objval.MapKeys()
+		count := len(keys)
+		r = make([]interface{}, count)
+		ctx = context.WithValue(ctx, rangeLen, count)
+		for i, key := range keys {
+			r[i] = realValue(e.elemExprNode.Run(
+				context.WithValue(
+					context.WithValue(
+						ctx,
+						rangeKey, key,
+					),
+					rangeValue, objval.MapIndex(key),
+				),
+				currField, tagExpr,
+			), e.boolOpposite, e.signOpposite)
+		}
+	default:
+	}
+	return r
+}
diff --git a/internal/tagexpr/spec_selector.go b/internal/tagexpr/spec_selector.go
new file mode 100644
index 0000000..7e00990
--- /dev/null
+++ b/internal/tagexpr/spec_selector.go
@@ -0,0 +1,109 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+type selectorExprNode struct {
+	exprBackground
+	field, name  string
+	subExprs     []ExprNode
+	boolOpposite *bool
+	signOpposite *bool
+}
+
+func (se *selectorExprNode) String() string {
+	return fmt.Sprintf("(%s)%s", se.field, se.name)
+}
+
+func (p *Expr) readSelectorExprNode(expr *string) ExprNode {
+	field, name, subSelector, boolOpposite, signOpposite, found := findSelector(expr)
+	if !found {
+		return nil
+	}
+	operand := &selectorExprNode{
+		field:        field,
+		name:         name,
+		boolOpposite: boolOpposite,
+		signOpposite: signOpposite,
+	}
+	operand.subExprs = make([]ExprNode, 0, len(subSelector))
+	for _, s := range subSelector {
+		grp := newGroupExprNode()
+		err := p.parseExprNode(&s, grp)
+		if err != nil {
+			return nil
+		}
+		sortPriority(grp)
+		operand.subExprs = append(operand.subExprs, grp)
+	}
+	return operand
+}
+
+var selectorRegexp = regexp.MustCompile(`^([\!\+\-]*)(\([ \t]*[A-Za-z_]+[A-Za-z0-9_\.]*[ \t]*\))?(\$)([\)\[\],\+\-\*\/%><\|&!=\^ \t\\]|$)`)
+
+func findSelector(expr *string) (field string, name string, subSelector []string, boolOpposite, signOpposite *bool, found bool) {
+	raw := *expr
+	a := selectorRegexp.FindAllStringSubmatch(raw, -1)
+	if len(a) != 1 {
+		return
+	}
+	r := a[0]
+	if s0 := r[2]; len(s0) > 0 {
+		field = strings.TrimSpace(s0[1 : len(s0)-1])
+	}
+	name = r[3]
+	*expr = (*expr)[len(a[0][0])-len(r[4]):]
+	for {
+		sub := readPairedSymbol(expr, '[', ']')
+		if sub == nil {
+			break
+		}
+		if *sub == "" || (*sub)[0] == '[' {
+			*expr = raw
+			return "", "", nil, nil, nil, false
+		}
+		subSelector = append(subSelector, strings.TrimSpace(*sub))
+	}
+	prefix := r[1]
+	if len(prefix) == 0 {
+		found = true
+		return
+	}
+	_, boolOpposite, signOpposite = getBoolAndSignOpposite(&prefix)
+	found = true
+	return
+}
+
+func (se *selectorExprNode) Run(ctx context.Context, currField string, tagExpr *TagExpr) interface{} {
+	var subFields []interface{}
+	if n := len(se.subExprs); n > 0 {
+		subFields = make([]interface{}, n)
+		for i, e := range se.subExprs {
+			subFields[i] = e.Run(ctx, currField, tagExpr)
+		}
+	}
+	field := se.field
+	if field == "" {
+		field = currField
+	}
+	v := tagExpr.getValue(field, subFields)
+	return realValue(v, se.boolOpposite, se.signOpposite)
+}
diff --git a/internal/tagexpr/tagexpr.go b/internal/tagexpr/tagexpr.go
new file mode 100644
index 0000000..9b14576
--- /dev/null
+++ b/internal/tagexpr/tagexpr.go
@@ -0,0 +1,1225 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package tagexpr is an interesting go struct tag expression syntax for field validation, etc.
+package tagexpr
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"sync"
+	"unsafe"
+)
+
+// Internally unified data types
+type (
+	Number  = float64
+	Null    = interface{}
+	Boolean = bool
+	String  = string
+)
+
+// VM struct tag expression interpreter
+type VM struct {
+	tagName   string
+	structJar map[uintptr]*structVM
+	rw        sync.RWMutex
+}
+
+// structVM tag expression set of struct
+type structVM struct {
+	vm                         *VM
+	name                       string
+	fields                     map[string]*fieldVM
+	fieldSelectorList          []string
+	fieldsWithIndirectStructVM []*fieldVM
+	exprs                      map[string]*Expr
+	exprSelectorList           []string
+	ifaceTagExprGetters        []func(unsafe.Pointer, string, func(*TagExpr, error) error) error
+	err                        error
+}
+
+// fieldVM tag expression set of struct field
+type fieldVM struct {
+	structField            reflect.StructField
+	ptrDeep                int
+	getPtr                 func(unsafe.Pointer) unsafe.Pointer
+	elemType               reflect.Type
+	elemKind               reflect.Kind
+	valueGetter            func(unsafe.Pointer) interface{}
+	reflectValueGetter     func(unsafe.Pointer, bool) reflect.Value
+	exprs                  map[string]*Expr
+	origin                 *structVM
+	mapKeyStructVM         *structVM
+	mapOrSliceElemStructVM *structVM
+	mapOrSliceIfaceKinds   [2]bool // [value, key/index]
+	fieldSelector          string
+	tagOp                  string
+}
+
+// New creates a tag expression interpreter that uses tagName as the tag name.
+// NOTE:
+//
+//	If no tagName is specified, no tag expression will be interpreted,
+//	but still can operate the various fields.
+func New(tagName ...string) *VM {
+	if len(tagName) == 0 {
+		tagName = append(tagName, "")
+	}
+	return &VM{
+		tagName:   tagName[0],
+		structJar: make(map[uintptr]*structVM, 256),
+	}
+}
+
+// MustRun is similar to Run, but panic when error.
+func (vm *VM) MustRun(structOrStructPtrOrReflectValue interface{}) *TagExpr {
+	te, err := vm.Run(structOrStructPtrOrReflectValue)
+	if err != nil {
+		panic(err)
+	}
+	return te
+}
+
+var (
+	unsupportedNil        = errors.New("unsupported data: nil")
+	unsupportedCannotAddr = errors.New("unsupported data: can not addr")
+)
+
+// Run returns the tag expression handler of the @structPtrOrReflectValue.
+// NOTE:
+//
+//	If the structure type has not been warmed up,
+//	it will be slower when it is first called.
+//
+// Disable new -d=checkptr behaviour for Go 1.14
+//
+//go:nocheckptr
+func (vm *VM) Run(structPtrOrReflectValue interface{}) (*TagExpr, error) {
+	var v reflect.Value
+	switch t := structPtrOrReflectValue.(type) {
+	case reflect.Value:
+		v = dereferenceValue(t)
+	default:
+		v = dereferenceValue(reflect.ValueOf(t))
+	}
+	if err := checkStructMapAddr(v); err != nil {
+		return nil, err
+	}
+
+	ptr := rvPtr(v)
+	if ptr == nil {
+		return nil, unsupportedNil
+	}
+
+	tid := rvType(v)
+	var err error
+	vm.rw.RLock()
+	s, ok := vm.structJar[tid]
+	vm.rw.RUnlock()
+	if !ok {
+		vm.rw.Lock()
+		s, ok = vm.structJar[tid]
+		if !ok {
+			s, err = vm.registerStructLocked(v.Type())
+			if err != nil {
+				vm.rw.Unlock()
+				return nil, err
+			}
+		}
+		vm.rw.Unlock()
+	}
+	if s.err != nil {
+		return nil, s.err
+	}
+	return s.newTagExpr(ptr, ""), nil
+}
+
+// RunAny returns the tag expression handler for the @v.
+// NOTE:
+//
+//	The @v can be structured data such as struct, map, slice, array, interface, reflcet.Value, etc.
+//	If the structure type has not been warmed up,
+//	it will be slower when it is first called.
+func (vm *VM) RunAny(v interface{}, fn func(*TagExpr, error) error) error {
+	vv, isReflectValue := v.(reflect.Value)
+	if !isReflectValue {
+		vv = reflect.ValueOf(v)
+	}
+	return vm.subRunAll(false, "", vv, fn)
+}
+
+// check type: struct{F map[T1]T2}
+func checkStructMapAddr(v reflect.Value) error {
+	if !v.IsValid() || v.CanAddr() || v.NumField() != 1 || v.Field(0).Kind() != reflect.Map {
+		return nil
+	}
+	return unsupportedCannotAddr
+}
+
+func (vm *VM) subRunAll(omitNil bool, tePath string, value reflect.Value, fn func(*TagExpr, error) error) error {
+	rv := dereferenceInterfaceValue(value)
+	if !rv.IsValid() {
+		return nil
+	}
+	rt := dereferenceType(rv.Type())
+	rv = dereferenceValue(rv)
+	switch rt.Kind() {
+	case reflect.Struct:
+		if len(tePath) == 0 {
+			if err := checkStructMapAddr(rv); err != nil {
+				return err
+			}
+		}
+		ptr := rvPtr(rv)
+		if ptr == nil {
+			if omitNil {
+				return nil
+			}
+			return fn(nil, unsupportedNil)
+		}
+		return fn(vm.subRun(tePath, rt, rvType(rv), ptr))
+
+	case reflect.Slice, reflect.Array:
+		count := rv.Len()
+		if count == 0 {
+			return nil
+		}
+		switch dereferenceType(rv.Type().Elem()).Kind() {
+		case reflect.Struct, reflect.Interface, reflect.Slice, reflect.Array, reflect.Map:
+			for i := count - 1; i >= 0; i-- {
+				err := vm.subRunAll(omitNil, tePath+"["+strconv.Itoa(i)+"]", rv.Index(i), fn)
+				if err != nil {
+					return err
+				}
+			}
+		default:
+			return nil
+		}
+
+	case reflect.Map:
+		if rv.Len() == 0 {
+			return nil
+		}
+		var canKey, canValue bool
+		rt := rv.Type()
+		switch dereferenceType(rt.Key()).Kind() {
+		case reflect.Struct, reflect.Interface, reflect.Slice, reflect.Array, reflect.Map:
+			canKey = true
+		}
+		switch dereferenceType(rt.Elem()).Kind() {
+		case reflect.Struct, reflect.Interface, reflect.Slice, reflect.Array, reflect.Map:
+			canValue = true
+		}
+		if !canKey && !canValue {
+			return nil
+		}
+		for _, key := range rv.MapKeys() {
+			if canKey {
+				err := vm.subRunAll(omitNil, tePath+"{k}", key, fn)
+				if err != nil {
+					return err
+				}
+			}
+			if canValue {
+				err := vm.subRunAll(omitNil, tePath+"{v for k="+key.String()+"}", rv.MapIndex(key), fn)
+				if err != nil {
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}
+
+func (vm *VM) subRun(path string, t reflect.Type, tid uintptr, ptr unsafe.Pointer) (*TagExpr, error) {
+	var err error
+	vm.rw.RLock()
+	s, ok := vm.structJar[tid]
+	vm.rw.RUnlock()
+	if !ok {
+		vm.rw.Lock()
+		s, ok = vm.structJar[tid]
+		if !ok {
+			s, err = vm.registerStructLocked(t)
+			if err != nil {
+				vm.rw.Unlock()
+				return nil, err
+			}
+		}
+		vm.rw.Unlock()
+	}
+	if s.err != nil {
+		return nil, s.err
+	}
+	return s.newTagExpr(ptr, path), nil
+}
+
+func (vm *VM) registerStructLocked(structType reflect.Type) (*structVM, error) {
+	structType, err := vm.getStructType(structType)
+	if err != nil {
+		return nil, err
+	}
+	tid := rtType(structType)
+	s, had := vm.structJar[tid]
+	if had {
+		return s, s.err
+	}
+	s = vm.newStructVM()
+	s.name = structType.String()
+	vm.structJar[tid] = s
+	numField := structType.NumField()
+	var structField reflect.StructField
+	var sub *structVM
+	for i := 0; i < numField; i++ {
+		structField = structType.Field(i)
+		field, ok, err := s.newFieldVM(structField)
+		if err != nil {
+			s.err = err
+			return nil, err
+		}
+		// skip omitted tag
+		if !ok {
+			continue
+		}
+		switch field.elemKind {
+		default:
+			field.setUnsupportedGetter()
+			switch field.elemKind {
+			case reflect.Struct:
+				sub, err = vm.registerStructLocked(field.structField.Type)
+				if err != nil {
+					s.err = err
+					return nil, err
+				}
+				s.mergeSubStructVM(field, sub)
+			case reflect.Interface:
+				s.setIfaceTagExprGetter(field)
+			}
+		case reflect.Float32, reflect.Float64,
+			reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+			field.setFloatGetter()
+		case reflect.String:
+			field.setStringGetter()
+		case reflect.Bool:
+			field.setBoolGetter()
+		case reflect.Array, reflect.Slice, reflect.Map:
+			err = vm.registerIndirectStructLocked(field)
+			if err != nil {
+				s.err = err
+				return nil, err
+			}
+		}
+	}
+	return s, nil
+}
+
+func (vm *VM) registerIndirectStructLocked(field *fieldVM) error {
+	field.setLengthGetter()
+	if field.tagOp == tagOmit {
+		return nil
+	}
+	a := make([]reflect.Type, 1, 2)
+	a[0] = derefType(field.elemType.Elem())
+	if field.elemKind == reflect.Map {
+		a = append(a, derefType(field.elemType.Key()))
+	}
+	for i, t := range a {
+		kind := t.Kind()
+		switch kind {
+		case reflect.Interface:
+			field.mapOrSliceIfaceKinds[i] = true
+			field.origin.fieldsWithIndirectStructVM = appendDistinct(field.origin.fieldsWithIndirectStructVM, field)
+		case reflect.Slice, reflect.Array, reflect.Map:
+			tt := t.Elem()
+			checkMap := kind == reflect.Map
+		F2:
+			for {
+				switch tt.Kind() {
+				case reflect.Slice, reflect.Array, reflect.Map, reflect.Ptr:
+					tt = tt.Elem()
+				case reflect.Struct:
+					_, err := vm.registerStructLocked(tt)
+					if err != nil {
+						return err
+					}
+					field.mapOrSliceIfaceKinds[i] = true
+					field.origin.fieldsWithIndirectStructVM = appendDistinct(field.origin.fieldsWithIndirectStructVM, field)
+					break F2
+				default:
+					break F2
+				}
+			}
+			if checkMap {
+				tt = t.Key()
+				checkMap = false
+				goto F2
+			}
+		case reflect.Struct:
+			s, err := vm.registerStructLocked(t)
+			if err != nil {
+				return err
+			}
+			if len(s.exprSelectorList) > 0 ||
+				len(s.ifaceTagExprGetters) > 0 ||
+				len(s.fieldsWithIndirectStructVM) > 0 {
+				if i == 0 {
+					field.mapOrSliceElemStructVM = s
+				} else {
+					field.mapKeyStructVM = s
+				}
+				field.origin.fieldsWithIndirectStructVM = appendDistinct(field.origin.fieldsWithIndirectStructVM, field)
+			}
+		}
+	}
+	return nil
+}
+
+func appendDistinct(a []*fieldVM, i *fieldVM) []*fieldVM {
+	has := false
+	for _, e := range a {
+		if e == i {
+			has = true
+			break
+		}
+	}
+	if !has {
+		return append(a, i)
+	}
+	return a
+}
+
+func (vm *VM) newStructVM() *structVM {
+	return &structVM{
+		vm:                         vm,
+		fields:                     make(map[string]*fieldVM, 32),
+		fieldSelectorList:          make([]string, 0, 32),
+		fieldsWithIndirectStructVM: make([]*fieldVM, 0, 32),
+		exprs:                      make(map[string]*Expr, 64),
+		exprSelectorList:           make([]string, 0, 64),
+	}
+}
+
+func (s *structVM) newFieldVM(structField reflect.StructField) (*fieldVM, bool, error) {
+	tag := structField.Tag.Get(s.vm.tagName)
+	if tag == tagOmit {
+		return nil, false, nil
+	}
+	f := &fieldVM{
+		structField:   structField,
+		exprs:         make(map[string]*Expr, 8),
+		origin:        s,
+		fieldSelector: structField.Name,
+	}
+	err := f.parseExprs(tag)
+	if err != nil {
+		return nil, false, err
+	}
+	s.fields[f.fieldSelector] = f
+	s.fieldSelectorList = append(s.fieldSelectorList, f.fieldSelector)
+
+	t := structField.Type
+	var ptrDeep int
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+		ptrDeep++
+	}
+	f.ptrDeep = ptrDeep
+
+	offset := structField.Offset
+	f.getPtr = func(ptr unsafe.Pointer) unsafe.Pointer {
+		if ptr == nil {
+			return nil
+		}
+		return unsafe.Pointer(uintptr(ptr) + offset)
+	}
+
+	f.elemType = t
+	f.elemKind = t.Kind()
+	f.reflectValueGetter = func(ptr unsafe.Pointer, initZero bool) reflect.Value {
+		v := f.packRawFrom(ptr)
+		if initZero {
+			f.ensureInit(v)
+		}
+		return v
+	}
+
+	return f, true, nil
+}
+
+func (f *fieldVM) ensureInit(v reflect.Value) {
+	if safeIsNil(v) && v.CanSet() {
+		newField := reflect.New(f.elemType).Elem()
+		for i := 0; i < f.ptrDeep; i++ {
+			if newField.CanAddr() {
+				newField = newField.Addr()
+			} else {
+				newField2 := reflect.New(newField.Type())
+				newField2.Elem().Set(newField)
+				newField = newField2
+			}
+		}
+		v.Set(newField)
+	}
+}
+
+func (s *structVM) mergeSubStructVM(field *fieldVM, sub *structVM) {
+	field.origin = sub
+	fieldsWithIndirectStructVM := make(map[*fieldVM]struct{}, len(sub.fieldsWithIndirectStructVM))
+	for _, subField := range sub.fieldsWithIndirectStructVM {
+		fieldsWithIndirectStructVM[subField] = struct{}{}
+	}
+	for _, k := range sub.fieldSelectorList {
+		v := sub.fields[k]
+		f := s.newChildField(field, v, true)
+		if _, ok := fieldsWithIndirectStructVM[v]; ok {
+			s.fieldsWithIndirectStructVM = append(s.fieldsWithIndirectStructVM, f)
+			// TODO: maybe needed?
+			// delete(fieldsWithIndirectStructVM, v)
+		}
+	}
+	// TODO: maybe needed?
+	// for v := range fieldsWithIndirectStructVM {
+	// 	f := s.newChildField(field, v, false)
+	// 	s.fieldsWithIndirectStructVM = append(s.fieldsWithIndirectStructVM, f)
+	// }
+
+	for _, _subFn := range sub.ifaceTagExprGetters {
+		subFn := _subFn
+		s.ifaceTagExprGetters = append(s.ifaceTagExprGetters, func(ptr unsafe.Pointer, pathPrefix string, fn func(*TagExpr, error) error) error {
+			ptr = field.getElemPtr(ptr)
+			if ptr == nil {
+				return nil
+			}
+			var path string
+			if pathPrefix == "" {
+				path = field.fieldSelector
+			} else {
+				path = pathPrefix + FieldSeparator + field.fieldSelector
+			}
+			return subFn(ptr, path, fn)
+		})
+	}
+}
+
+func (s *structVM) newChildField(parent *fieldVM, child *fieldVM, toBind bool) *fieldVM {
+	f := &fieldVM{
+		structField:            child.structField,
+		exprs:                  make(map[string]*Expr, len(child.exprs)),
+		ptrDeep:                child.ptrDeep,
+		elemType:               child.elemType,
+		elemKind:               child.elemKind,
+		origin:                 child.origin,
+		mapKeyStructVM:         child.mapKeyStructVM,
+		mapOrSliceElemStructVM: child.mapOrSliceElemStructVM,
+		mapOrSliceIfaceKinds:   child.mapOrSliceIfaceKinds,
+		fieldSelector:          parent.fieldSelector + FieldSeparator + child.fieldSelector,
+	}
+	if parent.tagOp != tagOmit {
+		f.tagOp = child.tagOp
+	} else {
+		f.tagOp = parent.tagOp
+	}
+	f.getPtr = func(ptr unsafe.Pointer) unsafe.Pointer {
+		ptr = parent.getElemPtr(ptr)
+		if ptr == nil {
+			return nil
+		}
+		return child.getPtr(ptr)
+	}
+	if child.valueGetter != nil {
+		if parent.ptrDeep == 0 {
+			f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+				return child.valueGetter(parent.getPtr(ptr))
+			}
+			f.reflectValueGetter = func(ptr unsafe.Pointer, initZero bool) reflect.Value {
+				return child.reflectValueGetter(parent.getPtr(ptr), initZero)
+			}
+		} else {
+			f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+				newField := reflect.NewAt(parent.structField.Type, parent.getPtr(ptr))
+				for i := 0; i < parent.ptrDeep; i++ {
+					newField = newField.Elem()
+				}
+				if newField.IsNil() {
+					return nil
+				}
+				return child.valueGetter(unsafe.Pointer(newField.Pointer()))
+			}
+			f.reflectValueGetter = func(ptr unsafe.Pointer, initZero bool) reflect.Value {
+				newField := reflect.NewAt(parent.structField.Type, parent.getPtr(ptr))
+				if initZero {
+					parent.ensureInit(newField.Elem())
+				}
+				for i := 0; i < parent.ptrDeep; i++ {
+					newField = newField.Elem()
+				}
+				if (newField == reflect.Value{}) || (!initZero && newField.IsNil()) {
+					return reflect.Value{}
+				}
+				return child.reflectValueGetter(unsafe.Pointer(newField.Pointer()), initZero)
+			}
+		}
+	}
+
+	if toBind {
+		s.fields[f.fieldSelector] = f
+		s.fieldSelectorList = append(s.fieldSelectorList, f.fieldSelector)
+		if parent.tagOp != tagOmit {
+			for k, v := range child.exprs {
+				selector := parent.fieldSelector + FieldSeparator + k
+				f.exprs[selector] = v
+				s.exprs[selector] = v
+				s.exprSelectorList = append(s.exprSelectorList, selector)
+			}
+		}
+	}
+	return f
+}
+
+func (f *fieldVM) getElemPtr(ptr unsafe.Pointer) unsafe.Pointer {
+	ptr = f.getPtr(ptr)
+	for i := f.ptrDeep; ptr != nil && i > 0; i-- {
+		ptr = ptrElem(ptr)
+	}
+	return ptr
+}
+
+func (f *fieldVM) packRawFrom(ptr unsafe.Pointer) reflect.Value {
+	return reflect.NewAt(f.structField.Type, f.getPtr(ptr)).Elem()
+}
+
+func (f *fieldVM) packElemFrom(ptr unsafe.Pointer) reflect.Value {
+	return reflect.NewAt(f.elemType, f.getElemPtr(ptr)).Elem()
+}
+
+func (s *structVM) setIfaceTagExprGetter(f *fieldVM) {
+	if f.tagOp == tagOmit {
+		return
+	}
+	s.ifaceTagExprGetters = append(s.ifaceTagExprGetters, func(ptr unsafe.Pointer, pathPrefix string, fn func(*TagExpr, error) error) error {
+		v := f.packElemFrom(ptr)
+		if !v.IsValid() || v.IsNil() {
+			return nil
+		}
+		var path string
+		if pathPrefix == "" {
+			path = f.fieldSelector
+		} else {
+			path = pathPrefix + FieldSeparator + f.fieldSelector
+		}
+		return s.vm.subRunAll(f.tagOp == tagOmitNil, path, v, fn)
+	})
+}
+
+func (f *fieldVM) setFloatGetter() {
+	if f.ptrDeep == 0 {
+		f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+			ptr = f.getPtr(ptr)
+			if ptr == nil {
+				return nil
+			}
+			return getFloat64(f.elemKind, ptr)
+		}
+	} else {
+		f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+			v := f.packElemFrom(ptr)
+			if v.CanAddr() {
+				return getFloat64(f.elemKind, unsafe.Pointer(v.UnsafeAddr()))
+			}
+			return nil
+		}
+	}
+}
+
+func (f *fieldVM) setBoolGetter() {
+	if f.ptrDeep == 0 {
+		f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+			ptr = f.getPtr(ptr)
+			if ptr == nil {
+				return nil
+			}
+			return *(*bool)(ptr)
+		}
+	} else {
+		f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+			v := f.packElemFrom(ptr)
+			if v.IsValid() {
+				return v.Bool()
+			}
+			return nil
+		}
+	}
+}
+
+func (f *fieldVM) setStringGetter() {
+	if f.ptrDeep == 0 {
+		f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+			ptr = f.getPtr(ptr)
+			if ptr == nil {
+				return nil
+			}
+			return *(*string)(ptr)
+		}
+	} else {
+		f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+			v := f.packElemFrom(ptr)
+			if v.IsValid() {
+				return v.String()
+			}
+			return nil
+		}
+	}
+}
+
+func (f *fieldVM) setLengthGetter() {
+	f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+		v := f.packElemFrom(ptr)
+		if v.IsValid() {
+			return v.Interface()
+		}
+		return nil
+	}
+}
+
+func (f *fieldVM) setUnsupportedGetter() {
+	f.valueGetter = func(ptr unsafe.Pointer) interface{} {
+		raw := f.packRawFrom(ptr)
+		if safeIsNil(raw) {
+			return nil
+		}
+		v := raw
+		for i := 0; i < f.ptrDeep; i++ {
+			v = v.Elem()
+		}
+		for v.Kind() == reflect.Interface {
+			v = v.Elem()
+		}
+		return anyValueGetter(raw, v)
+	}
+}
+
+func (vm *VM) getStructType(t reflect.Type) (reflect.Type, error) {
+	structType := t
+	for structType.Kind() == reflect.Ptr {
+		structType = structType.Elem()
+	}
+	if structType.Kind() != reflect.Struct {
+		return nil, fmt.Errorf("unsupported type: %s", t.String())
+	}
+	return structType, nil
+}
+
+func (s *structVM) newTagExpr(ptr unsafe.Pointer, path string) *TagExpr {
+	te := &TagExpr{
+		s:    s,
+		ptr:  ptr,
+		sub:  make(map[string]*TagExpr, 8),
+		path: strings.TrimPrefix(path, "."),
+	}
+	return te
+}
+
+// TagExpr struct tag expression evaluator
+type TagExpr struct {
+	s    *structVM
+	ptr  unsafe.Pointer
+	sub  map[string]*TagExpr
+	path string
+}
+
+// EvalFloat evaluates the value of the struct tag expression by the selector expression.
+// NOTE:
+//
+//	If the expression value type is not float64, return 0.
+func (t *TagExpr) EvalFloat(exprSelector string) float64 {
+	r, _ := t.Eval(exprSelector).(float64)
+	return r
+}
+
+// EvalString evaluates the value of the struct tag expression by the selector expression.
+// NOTE:
+//
+//	If the expression value type is not string, return "".
+func (t *TagExpr) EvalString(exprSelector string) string {
+	r, _ := t.Eval(exprSelector).(string)
+	return r
+}
+
+// EvalBool evaluates the value of the struct tag expression by the selector expression.
+// NOTE:
+//
+//	If the expression value is not 0, '' or nil, return true.
+func (t *TagExpr) EvalBool(exprSelector string) bool {
+	return FakeBool(t.Eval(exprSelector))
+}
+
+// FakeBool fakes any type as a boolean.
+func FakeBool(v interface{}) bool {
+	switch r := v.(type) {
+	case float64:
+		return r != 0
+	case float32:
+		return r != 0
+	case int:
+		return r != 0
+	case int8:
+		return r != 0
+	case int16:
+		return r != 0
+	case int32:
+		return r != 0
+	case int64:
+		return r != 0
+	case uint:
+		return r != 0
+	case uint8:
+		return r != 0
+	case uint16:
+		return r != 0
+	case uint32:
+		return r != 0
+	case uint64:
+		return r != 0
+	case string:
+		return r != ""
+	case bool:
+		return r
+	case nil, error:
+		return false
+	case []interface{}:
+		bol := true
+		for _, v := range r {
+			bol = bol && FakeBool(v)
+		}
+		return bol
+	default:
+		vv := dereferenceValue(reflect.ValueOf(v))
+		if vv.IsValid() || vv.IsZero() {
+			return false
+		}
+		return true
+	}
+}
+
+// Field returns the field handler specified by the selector.
+func (t *TagExpr) Field(fieldSelector string) (fh *FieldHandler, found bool) {
+	f, ok := t.s.fields[fieldSelector]
+	if !ok {
+		return nil, false
+	}
+	return newFieldHandler(t, fieldSelector, f), true
+}
+
+// RangeFields loop through each field.
+// When fn returns false, interrupt traversal and return false.
+func (t *TagExpr) RangeFields(fn func(*FieldHandler) bool) bool {
+	if list := t.s.fieldSelectorList; len(list) > 0 {
+		fields := t.s.fields
+		for _, fieldSelector := range list {
+			if !fn(newFieldHandler(t, fieldSelector, fields[fieldSelector])) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// Eval evaluates the value of the struct tag expression by the selector expression.
+// NOTE:
+//
+//	format: fieldName, fieldName.exprName, fieldName1.fieldName2.exprName1
+//	result types: float64, string, bool, nil
+func (t *TagExpr) Eval(exprSelector string) interface{} {
+	expr, ok := t.s.exprs[exprSelector]
+	if !ok {
+		// Compatible with single mode or the expression with the name @
+		if strings.HasSuffix(exprSelector, ExprNameSeparator) {
+			exprSelector = exprSelector[:len(exprSelector)-1]
+			if strings.HasSuffix(exprSelector, ExprNameSeparator) {
+				exprSelector = exprSelector[:len(exprSelector)-1]
+			}
+			expr, ok = t.s.exprs[exprSelector]
+		}
+		if !ok {
+			return nil
+		}
+	}
+	dir, base := splitFieldSelector(exprSelector)
+	targetTagExpr, err := t.checkout(dir)
+	if err != nil {
+		return nil
+	}
+	return expr.run(base, targetTagExpr)
+}
+
+// EvalWithEnv evaluates the value with the given env
+// NOTE:
+//
+//	format: fieldName, fieldName.exprName, fieldName1.fieldName2.exprName1
+//	result types: float64, string, bool, nil
+func (t *TagExpr) EvalWithEnv(exprSelector string, env map[string]interface{}) interface{} {
+	expr, ok := t.s.exprs[exprSelector]
+	if !ok {
+		// Compatible with single mode or the expression with the name @
+		if strings.HasSuffix(exprSelector, ExprNameSeparator) {
+			exprSelector = exprSelector[:len(exprSelector)-1]
+			if strings.HasSuffix(exprSelector, ExprNameSeparator) {
+				exprSelector = exprSelector[:len(exprSelector)-1]
+			}
+			expr, ok = t.s.exprs[exprSelector]
+		}
+		if !ok {
+			return nil
+		}
+	}
+	dir, base := splitFieldSelector(exprSelector)
+	targetTagExpr, err := t.checkout(dir)
+	if err != nil {
+		return nil
+	}
+	return expr.runWithEnv(base, targetTagExpr, env)
+}
+
+// Range loop through each tag expression.
+// When fn returns false, interrupt traversal and return false.
+// NOTE:
+//
+//	eval result types: float64, string, bool, nil
+func (t *TagExpr) Range(fn func(*ExprHandler) error) error {
+	var err error
+	if list := t.s.exprSelectorList; len(list) > 0 {
+		for _, es := range list {
+			dir, base := splitFieldSelector(es)
+			targetTagExpr, err := t.checkout(dir)
+			if err != nil {
+				continue
+			}
+			err = fn(newExprHandler(t, targetTagExpr, base, es))
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	ptr := t.ptr
+
+	if list := t.s.fieldsWithIndirectStructVM; len(list) > 0 {
+		for _, f := range list {
+			v := f.packElemFrom(ptr)
+			if !v.IsValid() {
+				continue
+			}
+			omitNil := f.tagOp == tagOmitNil
+			mapKeyStructVM := f.mapKeyStructVM
+			mapOrSliceElemStructVM := f.mapOrSliceElemStructVM
+			valueIface := f.mapOrSliceIfaceKinds[0]
+			keyIface := f.mapOrSliceIfaceKinds[1]
+
+			if f.elemKind == reflect.Map &&
+				(mapOrSliceElemStructVM != nil || mapKeyStructVM != nil || valueIface || keyIface) {
+				keyPath := f.fieldSelector + "{k}"
+				for _, key := range v.MapKeys() {
+					if mapKeyStructVM != nil {
+						p := rvPtr(derefValue(key))
+						if omitNil && p == nil {
+							continue
+						}
+						err = mapKeyStructVM.newTagExpr(p, keyPath).Range(fn)
+						if err != nil {
+							return err
+						}
+					} else if keyIface {
+						err = t.subRange(omitNil, keyPath, key, fn)
+						if err != nil {
+							return err
+						}
+					}
+					if mapOrSliceElemStructVM != nil {
+						p := rvPtr(derefValue(v.MapIndex(key)))
+						if omitNil && p == nil {
+							continue
+						}
+						err = mapOrSliceElemStructVM.newTagExpr(p, f.fieldSelector+"{v for k="+key.String()+"}").Range(fn)
+						if err != nil {
+							return err
+						}
+					} else if valueIface {
+						err = t.subRange(omitNil, f.fieldSelector+"{v for k="+key.String()+"}", v.MapIndex(key), fn)
+						if err != nil {
+							return err
+						}
+					}
+				}
+
+			} else if mapOrSliceElemStructVM != nil || valueIface {
+				// slice or array
+				for i := v.Len() - 1; i >= 0; i-- {
+					if mapOrSliceElemStructVM != nil {
+						p := rvPtr(derefValue(v.Index(i)))
+						if omitNil && p == nil {
+							continue
+						}
+						err = mapOrSliceElemStructVM.newTagExpr(p, f.fieldSelector+"["+strconv.Itoa(i)+"]").Range(fn)
+						if err != nil {
+							return err
+						}
+					} else if valueIface {
+						err = t.subRange(omitNil, f.fieldSelector+"["+strconv.Itoa(i)+"]", v.Index(i), fn)
+						if err != nil {
+							return err
+						}
+					}
+				}
+			}
+		}
+	}
+
+	if list := t.s.ifaceTagExprGetters; len(list) > 0 {
+		for _, getter := range list {
+			err = getter(ptr, "", func(te *TagExpr, err error) error {
+				if err != nil {
+					return err
+				}
+				return te.Range(fn)
+			})
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+func (t *TagExpr) subRange(omitNil bool, path string, value reflect.Value, fn func(*ExprHandler) error) error {
+	return t.s.vm.subRunAll(omitNil, path, value, func(te *TagExpr, err error) error {
+		if err != nil {
+			return err
+		}
+		return te.Range(fn)
+	})
+}
+
+var (
+	errFieldSelector = errors.New("field selector does not exist")
+	errOmitNil       = errors.New("omit nil")
+)
+
+func (t *TagExpr) checkout(fs string) (*TagExpr, error) {
+	if fs == "" {
+		return t, nil
+	}
+	subTagExpr, ok := t.sub[fs]
+	if ok {
+		if subTagExpr == nil {
+			return nil, errOmitNil
+		}
+		return subTagExpr, nil
+	}
+	f, ok := t.s.fields[fs]
+	if !ok {
+		return nil, errFieldSelector
+	}
+	ptr := f.getElemPtr(t.ptr)
+	if f.tagOp == tagOmitNil && ptr == nil {
+		t.sub[fs] = nil
+		return nil, errOmitNil
+	}
+	subTagExpr = f.origin.newTagExpr(ptr, t.path)
+	t.sub[fs] = subTagExpr
+	return subTagExpr, nil
+}
+
+func (t *TagExpr) getValue(fieldSelector string, subFields []interface{}) (v interface{}) {
+	f := t.s.fields[fieldSelector]
+	if f == nil {
+		return nil
+	}
+	if f.valueGetter == nil {
+		return nil
+	}
+	v = f.valueGetter(t.ptr)
+	if v == nil {
+		return nil
+	}
+	if len(subFields) == 0 {
+		return v
+	}
+	vv := reflect.ValueOf(v)
+	var kind reflect.Kind
+	for i, k := range subFields {
+		kind = vv.Kind()
+		for kind == reflect.Ptr || kind == reflect.Interface {
+			vv = vv.Elem()
+			kind = vv.Kind()
+		}
+		switch kind {
+		case reflect.Slice, reflect.Array, reflect.String:
+			if float, ok := k.(float64); ok {
+				idx := int(float)
+				if idx >= vv.Len() {
+					return nil
+				}
+				vv = vv.Index(idx)
+			} else {
+				return nil
+			}
+		case reflect.Map:
+			k := safeConvert(reflect.ValueOf(k), vv.Type().Key())
+			if !k.IsValid() {
+				return nil
+			}
+			vv = vv.MapIndex(k)
+		case reflect.Struct:
+			if float, ok := k.(float64); ok {
+				idx := int(float)
+				if idx < 0 || idx >= vv.NumField() {
+					return nil
+				}
+				vv = vv.Field(idx)
+			} else if str, ok := k.(string); ok {
+				vv = vv.FieldByName(str)
+			} else {
+				return nil
+			}
+		default:
+			if i < len(subFields)-1 {
+				return nil
+			}
+		}
+		if !vv.IsValid() {
+			return nil
+		}
+	}
+	raw := vv
+	for vv.Kind() == reflect.Ptr || vv.Kind() == reflect.Interface {
+		vv = vv.Elem()
+	}
+	return anyValueGetter(raw, vv)
+}
+
+func safeConvert(v reflect.Value, t reflect.Type) reflect.Value {
+	defer func() { recover() }()
+	return v.Convert(t)
+}
+
+func splitFieldSelector(selector string) (dir, base string) {
+	idx := strings.LastIndex(selector, ExprNameSeparator)
+	if idx != -1 {
+		selector = selector[:idx]
+	}
+	idx = strings.LastIndex(selector, FieldSeparator)
+	if idx != -1 {
+		return selector[:idx], selector[idx+1:]
+	}
+	return "", selector
+}
+
+func getFloat64(kind reflect.Kind, p unsafe.Pointer) interface{} {
+	switch kind {
+	case reflect.Float32:
+		return float64(*(*float32)(p))
+	case reflect.Float64:
+		return *(*float64)(p)
+	case reflect.Int:
+		return float64(*(*int)(p))
+	case reflect.Int8:
+		return float64(*(*int8)(p))
+	case reflect.Int16:
+		return float64(*(*int16)(p))
+	case reflect.Int32:
+		return float64(*(*int32)(p))
+	case reflect.Int64:
+		return float64(*(*int64)(p))
+	case reflect.Uint:
+		return float64(*(*uint)(p))
+	case reflect.Uint8:
+		return float64(*(*uint8)(p))
+	case reflect.Uint16:
+		return float64(*(*uint16)(p))
+	case reflect.Uint32:
+		return float64(*(*uint32)(p))
+	case reflect.Uint64:
+		return float64(*(*uint64)(p))
+	case reflect.Uintptr:
+		return float64(*(*uintptr)(p))
+	}
+	return nil
+}
+
+func anyValueGetter(raw, elem reflect.Value) interface{} {
+	if !elem.IsValid() || !raw.IsValid() {
+		return nil
+	}
+	kind := elem.Kind()
+	switch kind {
+	case reflect.Float32, reflect.Float64,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if elem.CanAddr() {
+			return getFloat64(kind, unsafe.Pointer(elem.UnsafeAddr()))
+		}
+		switch kind {
+		case reflect.Float32, reflect.Float64:
+			return elem.Float()
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			return float64(elem.Int())
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+			return float64(elem.Uint())
+		}
+	case reflect.String:
+		return elem.String()
+	case reflect.Bool:
+		return elem.Bool()
+	}
+	if raw.CanInterface() {
+		return raw.Interface()
+	}
+	return nil
+}
+
+func safeIsNil(v reflect.Value) bool {
+	if !v.IsValid() {
+		return true
+	}
+	switch v.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr,
+		reflect.UnsafePointer, reflect.Interface, reflect.Slice:
+		return v.IsNil()
+	}
+	return false
+}
+
+//go:nocheckptr
+func ptrElem(ptr unsafe.Pointer) unsafe.Pointer {
+	return unsafe.Pointer(*(*uintptr)(ptr))
+}
+
+func derefType(t reflect.Type) reflect.Type {
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t
+}
+
+func derefValue(v reflect.Value) reflect.Value {
+	for v.Kind() == reflect.Ptr {
+		v = v.Elem()
+	}
+	return v
+}
diff --git a/internal/tagexpr/tagparser.go b/internal/tagexpr/tagparser.go
new file mode 100644
index 0000000..fd95478
--- /dev/null
+++ b/internal/tagexpr/tagparser.go
@@ -0,0 +1,190 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+)
+
+const (
+	tagOmit    = "-"
+	tagOmitNil = "?"
+)
+
+func (f *fieldVM) parseExprs(tag string) error {
+	switch tag {
+	case tagOmit, tagOmitNil:
+		f.tagOp = tag
+		return nil
+	}
+
+	kvs, err := parseTag(tag)
+	if err != nil {
+		return err
+	}
+	exprSelectorPrefix := f.structField.Name
+
+	for exprSelector, exprString := range kvs {
+		expr, err := parseExpr(exprString)
+		if err != nil {
+			return err
+		}
+		if exprSelector == ExprNameSeparator {
+			exprSelector = exprSelectorPrefix
+		} else {
+			exprSelector = exprSelectorPrefix + ExprNameSeparator + exprSelector
+		}
+		f.exprs[exprSelector] = expr
+		f.origin.exprs[exprSelector] = expr
+		f.origin.exprSelectorList = append(f.origin.exprSelectorList, exprSelector)
+	}
+	return nil
+}
+
+func parseTag(tag string) (map[string]string, error) {
+	s := tag
+	ptr := &s
+	kvs := make(map[string]string)
+	for {
+		one, err := readOneExpr(ptr)
+		if err != nil {
+			return nil, err
+		}
+		if one == "" {
+			return kvs, nil
+		}
+		key, val := splitExpr(one)
+		if val == "" {
+			return nil, fmt.Errorf("syntax error: %q expression string can not be empty", tag)
+		}
+		if _, ok := kvs[key]; ok {
+			return nil, fmt.Errorf("syntax error: %q duplicate expression name %q", tag, key)
+		}
+		kvs[key] = val
+	}
+}
+
+func splitExpr(one string) (key, val string) {
+	one = strings.TrimSpace(one)
+	if one == "" {
+		return DefaultExprName, ""
+	}
+	var rs []rune
+	for _, r := range one {
+		if r == '@' ||
+			r == '_' ||
+			(r >= '0' && r <= '9') ||
+			(r >= 'A' && r <= 'Z') ||
+			(r >= 'a' && r <= 'z') {
+			rs = append(rs, r)
+		} else {
+			break
+		}
+	}
+	key = string(rs)
+	val = strings.TrimSpace(one[len(key):])
+	if val == "" || val[0] != ':' {
+		return DefaultExprName, one
+	}
+	val = val[1:]
+	if key == "" {
+		key = DefaultExprName
+	}
+	return key, val
+}
+
+func readOneExpr(tag *string) (string, error) {
+	s := *(trimRightSpace(trimLeftSpace(tag)))
+	s = strings.TrimLeft(s, ";")
+	if s == "" {
+		return "", nil
+	}
+	if s[len(s)-1] != ';' {
+		s += ";"
+	}
+	a := strings.SplitAfter(strings.Replace(s, "\\'", "##", -1), ";")
+	idx := -1
+	var patch int
+	for _, v := range a {
+		idx += len(v)
+		count := strings.Count(v, "'")
+		if (count+patch)%2 == 0 {
+			*tag = s[idx+1:]
+			return s[:idx], nil
+		}
+		if count > 0 {
+			patch++
+		}
+	}
+	return "", fmt.Errorf("syntax error: %q unclosed single quote \"'\"", s)
+}
+
+func trimLeftSpace(p *string) *string {
+	*p = strings.TrimLeftFunc(*p, unicode.IsSpace)
+	return p
+}
+
+func trimRightSpace(p *string) *string {
+	*p = strings.TrimRightFunc(*p, unicode.IsSpace)
+	return p
+}
+
+func readPairedSymbol(p *string, left, right rune) *string {
+	s := *p
+	if len(s) == 0 || rune(s[0]) != left {
+		return nil
+	}
+	s = s[1:]
+	last1 := left
+	var last2 rune
+	var leftLevel, rightLevel int
+	escapeIndexes := make(map[int]bool)
+	var realEqual, escapeEqual bool
+	for i, r := range s {
+		if realEqual, escapeEqual = equalRune(right, r, last1, last2); realEqual {
+			if leftLevel == rightLevel {
+				*p = s[i+1:]
+				sub := make([]rune, 0, i)
+				for k, v := range s[:i] {
+					if !escapeIndexes[k] {
+						sub = append(sub, v)
+					}
+				}
+				s = string(sub)
+				return &s
+			}
+			rightLevel++
+		} else if escapeEqual {
+			escapeIndexes[i-1] = true
+		} else if realEqual, escapeEqual = equalRune(left, r, last1, last2); realEqual {
+			leftLevel++
+		} else if escapeEqual {
+			escapeIndexes[i-1] = true
+		}
+		last2 = last1
+		last1 = r
+	}
+	return nil
+}
+
+func equalRune(a, b, last1, last2 rune) (real, escape bool) {
+	if a == b {
+		real = last1 != '\\' || last2 == '\\'
+		escape = last1 == '\\' && last2 != '\\'
+	}
+	return
+}
diff --git a/internal/tagexpr/utils.go b/internal/tagexpr/utils.go
new file mode 100644
index 0000000..11b3ca6
--- /dev/null
+++ b/internal/tagexpr/utils.go
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2024 CloudWeGo Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package tagexpr
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+func init() {
+	testhack()
+}
+
+func dereferenceValue(v reflect.Value) reflect.Value {
+	for v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface {
+		v = v.Elem()
+	}
+	return v
+}
+
+func dereferenceType(t reflect.Type) reflect.Type {
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t
+}
+
+func dereferenceInterfaceValue(v reflect.Value) reflect.Value {
+	for v.Kind() == reflect.Interface {
+		v = v.Elem()
+	}
+	return v
+}
+
+type rvtype struct { // reflect.Value
+	abiType uintptr
+	ptr     unsafe.Pointer // data pointer
+}
+
+func rvPtr(rv reflect.Value) unsafe.Pointer {
+	return (*rvtype)(unsafe.Pointer(&rv)).ptr
+}
+
+func rvType(rv reflect.Value) uintptr {
+	return (*rvtype)(unsafe.Pointer(&rv)).abiType
+}
+
+func rtType(rt reflect.Type) uintptr {
+	type iface struct {
+		tab  uintptr
+		data uintptr
+	}
+	return (*iface)(unsafe.Pointer(&rt)).data
+}
+
+// quick test make sure the hack above works
+func testhack() {
+	type T1 struct {
+		a int
+	}
+	type T2 struct {
+		a int
+	}
+	p0 := &T1{1}
+	p1 := &T1{2}
+	p2 := &T2{3}
+
+	if rvPtr(reflect.ValueOf(p0)) != unsafe.Pointer(p0) ||
+		rvPtr(reflect.ValueOf(p0).Elem()) != unsafe.Pointer(p0) ||
+		rvPtr(reflect.ValueOf(p0)) == rvPtr(reflect.ValueOf(p1)) {
+		panic("rvPtr() compatibility issue found")
+	}
+
+	if rvType(reflect.ValueOf(p0)) != rvType(reflect.ValueOf(p1)) ||
+		rvType(reflect.ValueOf(p0)) == rvType(reflect.ValueOf(p2)) ||
+		rvType(reflect.ValueOf(p0).Elem()) != rvType(reflect.ValueOf(p1).Elem()) ||
+		rvType(reflect.ValueOf(p0).Elem()) == rvType(reflect.ValueOf(p2).Elem()) {
+		panic("rvType() compatibility issue found")
+	}
+
+	if rtType(reflect.TypeOf(p0)) != rtType(reflect.TypeOf(p1)) ||
+		rtType(reflect.TypeOf(p0)) == rtType(reflect.TypeOf(p2)) ||
+		rtType(reflect.TypeOf(p0).Elem()) != rtType(reflect.TypeOf(p1).Elem()) ||
+		rtType(reflect.TypeOf(p0).Elem()) == rtType(reflect.TypeOf(p2).Elem()) {
+		panic("rtType() compatibility issue found")
+	}
+}
diff --git a/internal/tagexpr/validator/README.md b/internal/tagexpr/validator/README.md
new file mode 100644
index 0000000..b3321a6
--- /dev/null
+++ b/internal/tagexpr/validator/README.md
@@ -0,0 +1,204 @@
+# validator [![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg?style=flat-square)](http://godoc.org/github.com/bytedance/go-tagexpr/v2/validator)
+
+A powerful validator that supports struct tag expression.
+
+## Feature
+
+- Support for a variety of common operator
+- Support for accessing arrays, slices, members of the dictionary
+- Support access to any field in the current structure
+- Support access to nested fields, non-exported fields, etc.
+- Support registers validator function expression
+- Built-in len, sprintf, regexp, email, phone functions
+- Support simple mode, or specify error message mode
+- Use offset pointers to directly take values, better performance
+- Required go version ≥1.9
+
+## Example
+
+```go
+package validator_test
+
+import (
+	"fmt"
+
+	vd "github.com/bytedance/go-tagexpr/v2/validator"
+)
+
+func Example() {
+	type InfoRequest struct {
+		Name         string   `vd:"($!='Alice'||(Age)$==18) && regexp('\\w')"`
+		Age          int      `vd:"$>0"`
+		Email        string   `vd:"email($)"`
+		Phone1       string   `vd:"phone($)"`
+		OtherPhones  []string `vd:"range($, phone(#v,'CN'))"`
+		*InfoRequest `vd:"?"`
+		Info1        *InfoRequest `vd:"?"`
+		Info2        *InfoRequest `vd:"-"`
+	}
+	info := &InfoRequest{
+		Name:        "Alice",
+		Age:         18,
+		Email:       "henrylee2cn@gmail.com",
+		Phone1:      "+8618812345678",
+		OtherPhones: []string{"18812345679", "18812345680"},
+	}
+	fmt.Println(vd.Validate(info))
+
+	type A struct {
+		A    int `vd:"$<0||$>=100"`
+		Info interface{}
+	}
+	info.Email = "xxx"
+	a := &A{A: 107, Info: info}
+	fmt.Println(vd.Validate(a))
+	type B struct {
+		B string `vd:"len($)>1 && regexp('^\\w*$')"`
+	}
+	b := &B{"abc"}
+	fmt.Println(vd.Validate(b) == nil)
+
+	type C struct {
+		C bool `vd:"@:(S.A)$>0 && !$; msg:'C must be false when S.A>0'"`
+		S *A
+	}
+	c := &C{C: true, S: a}
+	fmt.Println(vd.Validate(c))
+
+	type D struct {
+		d []string `vd:"@:len($)>0 && $[0]=='D'; msg:sprintf('invalid d: %v',$)"`
+	}
+	d := &D{d: []string{"x", "y"}}
+	fmt.Println(vd.Validate(d))
+
+	type E struct {
+		e map[string]int `vd:"len($)==$['len']"`
+	}
+	e := &E{map[string]int{"len": 2}}
+	fmt.Println(vd.Validate(e))
+
+	// Customizes the factory of validation error.
+	vd.SetErrorFactory(func(failPath, msg string) error {
+		return fmt.Errorf(`{"succ":false, "error":"validation failed: %s"}`, failPath)
+	})
+
+	type F struct {
+		f struct {
+			g int `vd:"$%3==0"`
+		}
+	}
+	f := &F{}
+	f.f.g = 10
+	fmt.Println(vd.Validate(f))
+
+	fmt.Println(vd.Validate(map[string]*F{"a": f}))
+	fmt.Println(vd.Validate(map[string]map[string]*F{"a": {"b": f}}))
+	fmt.Println(vd.Validate([]map[string]*F{{"a": f}}))
+	fmt.Println(vd.Validate(struct {
+		A []map[string]*F
+	}{A: []map[string]*F{{"x": f}}}))
+	fmt.Println(vd.Validate(map[*F]int{f: 1}))
+	fmt.Println(vd.Validate([][1]*F{{f}}))
+	fmt.Println(vd.Validate((*F)(nil)))
+	fmt.Println(vd.Validate(map[string]*F{}))
+	fmt.Println(vd.Validate(map[string]map[string]*F{}))
+	fmt.Println(vd.Validate([]map[string]*F{}))
+	fmt.Println(vd.Validate([]*F{}))
+
+	// Output:
+	// <nil>
+	// email format is incorrect
+	// true
+	// C must be false when S.A>0
+	// invalid d: [x y]
+	// invalid parameter: e
+	// {"succ":false, "error":"validation failed: f.g"}
+	// {"succ":false, "error":"validation failed: {v for k=a}.f.g"}
+	// {"succ":false, "error":"validation failed: {v for k=a}{v for k=b}.f.g"}
+	// {"succ":false, "error":"validation failed: [0]{v for k=a}.f.g"}
+	// {"succ":false, "error":"validation failed: A[0]{v for k=x}.f.g"}
+	// {"succ":false, "error":"validation failed: {k}.f.g"}
+	// {"succ":false, "error":"validation failed: [0][0].f.g"}
+	// unsupported data: nil
+	// <nil>
+	// <nil>
+	// <nil>
+	// <nil>
+}
+```
+
+## Syntax
+
+Struct tag syntax spec:
+
+```
+type T struct {
+	// Simple model
+    Field1 T1 `tagName:"expression"`
+	// Specify error message mode
+    Field2 T2 `tagName:"@:expression; msg:expression2"`
+	// Omit it
+    Field3 T3 `tagName:"-"`
+    // Omit it when it is nil
+    Field4 T4 `tagName:"?"`
+    ...
+}
+```
+
+|Operator or Operand|Explain|
+|-----|---------|
+|`true` `false`|boolean|
+|`0` `0.0`|float64 "0"|
+|`''`|String|
+|`\\'`| Escape `'` delims in string|
+|`\"`| Escape `"` delims in string|
+|`nil`|nil, undefined|
+|`!`|not|
+|`+`|Digital addition or string splicing|
+|`-`|Digital subtraction or negative|
+|`*`|Digital multiplication|
+|`/`|Digital division|
+|`%`|division remainder, as: `float64(int64(a)%int64(b))`|
+|`==`|`eq`|
+|`!=`|`ne`|
+|`>`|`gt`|
+|`>=`|`ge`|
+|`<`|`lt`|
+|`<=`|`le`|
+|`&&`|Logic `and`|
+|`\|\|`|Logic `or`|
+|`()`|Expression group|
+|`(X)$`|Struct field value named X|
+|`(X.Y)$`|Struct field value named X.Y|
+|`$`|Shorthand for `(X)$`, omit `(X)` to indicate current struct field value|
+|`(X)$['A']`|Map value with key A or struct A sub-field in the struct field X|
+|`(X)$[0]`|The 0th element or sub-field of the struct field X(type: map, slice, array, struct)|
+|`len((X)$)`|Built-in function `len`, the length of struct field X|
+|`mblen((X)$)`|the length of string field X (character number)|
+|`regexp('^\\w*$', (X)$)`|Regular match the struct field X, return boolean|
+|`regexp('^\\w*$')`|Regular match the current struct field, return boolean|
+|`sprintf('X value: %v', (X)$)`|`fmt.Sprintf`, format the value of struct field X|
+|`range(KvExpr, forEachExpr)`|Iterate over an array, slice, or dictionary <br> - `#k` is the element key var <br> - `#v` is the element value var <br> - `##` is the number of elements <br> - e.g. [example](../spec_range_test.go)|
+|`in((X)$, enum_1, ...enum_n)`|Check if the first parameter is one of the enumerated parameters|
+|`email((X)$)`|Regular match the struct field X, return true if it is email|
+|`phone((X)$,<'defaultRegion'>)`|Regular match the struct field X, return true if it is phone|
+
+<!-- |`(X)$k`|Traverse each element key of the struct field X(type: map, slice, array)|
+|`(X)$v`|Traverse each element value of the struct field X(type: map, slice, array)| -->
+
+<!-- |`&`|Integer bitwise `and`|
+|`\|`|Integer bitwise `or`|
+|`^`|Integer bitwise `not` or `xor`|
+|`&^`|Integer bitwise `clean`|
+|`<<`|Integer bitwise `shift left`|
+|`>>`|Integer bitwise `shift right`| -->
+
+Operator priority(high -> low):
+
+* `()` `!` `bool` `float64` `string` `nil`
+* `*` `/` `%`
+* `+` `-`
+* `<` `<=` `>` `>=`
+* `==` `!=`
+* `&&`
+* `||`
diff --git a/internal/tagexpr/validator/default.go b/internal/tagexpr/validator/default.go
new file mode 100644
index 0000000..667b5f5
--- /dev/null
+++ b/internal/tagexpr/validator/default.go
@@ -0,0 +1,42 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validator
+
+var defaultValidator = New("vd").SetErrorFactory(defaultErrorFactory)
+
+// Default returns the default validator.
+// NOTE:
+//
+//	The tag name is 'vd'
+func Default() *Validator {
+	return defaultValidator
+}
+
+// Validate uses the default validator to validate whether the fields of value is valid.
+// NOTE:
+//
+//	The tag name is 'vd'
+//	If checkAll=true, validate all the error.
+func Validate(value interface{}, checkAll ...bool) error {
+	return defaultValidator.Validate(value, checkAll...)
+}
+
+// SetErrorFactory customizes the factory of validation error for the default validator.
+// NOTE:
+//
+//	The tag name is 'vd'
+func SetErrorFactory(errFactory func(fieldSelector, msg string) error) {
+	defaultValidator.SetErrorFactory(errFactory)
+}
diff --git a/internal/tagexpr/validator/func.go b/internal/tagexpr/validator/func.go
new file mode 100644
index 0000000..17800cc
--- /dev/null
+++ b/internal/tagexpr/validator/func.go
@@ -0,0 +1,116 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validator
+
+import (
+	"errors"
+	"regexp"
+
+	"github.com/nyaruka/phonenumbers"
+
+	"github.com/cloudwego/hertz/internal/tagexpr"
+)
+
+// ErrInvalidWithoutMsg verification error without error message.
+var ErrInvalidWithoutMsg = errors.New("")
+
+// MustRegFunc registers validator function expression.
+// NOTE:
+//
+//	panic if exist error;
+//	example: phone($) or phone($,'CN');
+//	If @force=true, allow to cover the existed same @funcName;
+//	The go number types always are float64;
+//	The go string types always are string.
+func MustRegFunc(funcName string, fn func(args ...interface{}) error, force ...bool) {
+	err := RegFunc(funcName, fn, force...)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// RegFunc registers validator function expression.
+// NOTE:
+//
+//	example: phone($) or phone($,'CN');
+//	If @force=true, allow to cover the existed same @funcName;
+//	The go number types always are float64;
+//	The go string types always are string.
+func RegFunc(funcName string, fn func(args ...interface{}) error, force ...bool) error {
+	return tagexpr.RegFunc(funcName, func(args ...interface{}) interface{} {
+		err := fn(args...)
+		if err == nil {
+			// nil defaults to false, so returns true
+			return true
+		}
+		return err
+	}, force...)
+}
+
+func init() {
+	pattern := "^([A-Za-z0-9_\\-\\.\u4e00-\u9fa5])+\\@([A-Za-z0-9_\\-\\.])+\\.([A-Za-z]{2,8})$"
+	emailRegexp := regexp.MustCompile(pattern)
+	MustRegFunc("email", func(args ...interface{}) error {
+		if len(args) != 1 {
+			return errors.New("number of parameters of email function is not one")
+		}
+		s, ok := args[0].(string)
+		if !ok {
+			return errors.New("parameter of email function is not string type")
+		}
+		matched := emailRegexp.MatchString(s)
+		if !matched {
+			// return ErrInvalidWithoutMsg
+			return errors.New("email format is incorrect")
+		}
+		return nil
+	}, true)
+}
+
+func init() {
+	// phone: defaultRegion is 'CN'
+	MustRegFunc("phone", func(args ...interface{}) error {
+		var numberToParse, defaultRegion string
+		var ok bool
+		switch len(args) {
+		default:
+			return errors.New("the number of parameters of phone function is not one or two")
+		case 2:
+			defaultRegion, ok = args[1].(string)
+			if !ok {
+				return errors.New("the 2nd parameter of phone function is not string type")
+			}
+			fallthrough
+		case 1:
+			numberToParse, ok = args[0].(string)
+			if !ok {
+				return errors.New("the 1st parameter of phone function is not string type")
+			}
+		}
+		if defaultRegion == "" {
+			defaultRegion = "CN"
+		}
+		num, err := phonenumbers.Parse(numberToParse, defaultRegion)
+		if err != nil {
+			return err
+		}
+		matched := phonenumbers.IsValidNumber(num)
+		if !matched {
+			// return ErrInvalidWithoutMsg
+			return errors.New("phone format is incorrect")
+		}
+		return nil
+	}, true)
+}
diff --git a/internal/tagexpr/validator/validator.go b/internal/tagexpr/validator/validator.go
new file mode 100644
index 0000000..2c57010
--- /dev/null
+++ b/internal/tagexpr/validator/validator.go
@@ -0,0 +1,163 @@
+// Package validator is a powerful validator that supports struct tag expression.
+//
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package validator
+
+import (
+	"errors"
+	"io"
+	"reflect"
+	"strings"
+	_ "unsafe"
+
+	"github.com/cloudwego/hertz/internal/tagexpr"
+)
+
+const (
+	// MatchExprName the name of the expression used for validation
+	MatchExprName = tagexpr.DefaultExprName
+	// ErrMsgExprName the name of the expression used to specify the message
+	// returned when validation failed
+	ErrMsgExprName = "msg"
+)
+
+// Validator struct fields validator
+type Validator struct {
+	vm         *tagexpr.VM
+	errFactory func(failPath, msg string) error
+}
+
+// New creates a struct fields validator.
+func New(tagName string) *Validator {
+	v := &Validator{
+		vm:         tagexpr.New(tagName),
+		errFactory: defaultErrorFactory,
+	}
+	return v
+}
+
+// VM returns the struct tag expression interpreter.
+func (v *Validator) VM() *tagexpr.VM {
+	return v.vm
+}
+
+// Validate validates whether the fields of value is valid.
+// NOTE:
+//
+//	If checkAll=true, validate all the error.
+func (v *Validator) Validate(value interface{}, checkAll ...bool) error {
+	var all bool
+	if len(checkAll) > 0 {
+		all = checkAll[0]
+	}
+	errs := make([]error, 0, 8)
+	err := v.vm.RunAny(value, func(te *tagexpr.TagExpr, err error) error {
+		if err != nil {
+			errs = append(errs, err)
+			if all {
+				return nil
+			}
+			return io.EOF
+		}
+		nilParentFields := make(map[string]bool, 16)
+		err = te.Range(func(eh *tagexpr.ExprHandler) error {
+			if strings.Contains(eh.StringSelector(), tagexpr.ExprNameSeparator) {
+				return nil
+			}
+			r := eh.Eval()
+			if r == nil {
+				return nil
+			}
+			rerr, ok := r.(error)
+			if !ok && tagexpr.FakeBool(r) {
+				return nil
+			}
+			// Ignore this error if the value of the parent is nil
+			if pfs, ok := eh.ExprSelector().ParentField(); ok {
+				if nilParentFields[pfs] {
+					return nil
+				}
+				if fh, ok := eh.TagExpr().Field(pfs); ok {
+					v := fh.Value(false)
+					if !v.IsValid() || (v.Kind() == reflect.Ptr && v.IsNil()) {
+						nilParentFields[pfs] = true
+						return nil
+					}
+				}
+			}
+			msg := eh.TagExpr().EvalString(eh.StringSelector() + tagexpr.ExprNameSeparator + ErrMsgExprName)
+			if msg == "" && rerr != nil {
+				msg = rerr.Error()
+			}
+			errs = append(errs, v.errFactory(eh.Path(), msg))
+			if all {
+				return nil
+			}
+			return io.EOF
+		})
+		if err != nil && !all {
+			return err
+		}
+		return nil
+	})
+	if err != io.EOF && err != nil {
+		return err
+	}
+	switch len(errs) {
+	case 0:
+		return nil
+	case 1:
+		return errs[0]
+	default:
+		var errStr string
+		for _, e := range errs {
+			errStr += e.Error() + "\t"
+		}
+		return errors.New(errStr[:len(errStr)-1])
+	}
+}
+
+// SetErrorFactory customizes the factory of validation error.
+// NOTE:
+//
+//	If errFactory==nil, the default is used
+func (v *Validator) SetErrorFactory(errFactory func(failPath, msg string) error) *Validator {
+	if errFactory == nil {
+		errFactory = defaultErrorFactory
+	}
+	v.errFactory = errFactory
+	return v
+}
+
+// Error validate error
+type Error struct {
+	FailPath, Msg string
+}
+
+// Error implements error interface.
+func (e *Error) Error() string {
+	if e.Msg != "" {
+		return e.Msg
+	}
+	return "invalid parameter: " + e.FailPath
+}
+
+//go:nosplit
+func defaultErrorFactory(failPath, msg string) error {
+	return &Error{
+		FailPath: failPath,
+		Msg:      msg,
+	}
+}
diff --git a/pkg/app/server/binding/config.go b/pkg/app/server/binding/config.go
index 81cf30e..4ee349e 100644
--- a/pkg/app/server/binding/config.go
+++ b/pkg/app/server/binding/config.go
@@ -22,7 +22,7 @@ import (
 	"reflect"
 	"time"
 
-	exprValidator "github.com/bytedance/go-tagexpr/v2/validator"
+	exprValidator "github.com/cloudwego/hertz/internal/tagexpr/validator"
 	inDecoder "github.com/cloudwego/hertz/pkg/app/server/binding/internal/decoder"
 	hJson "github.com/cloudwego/hertz/pkg/common/json"
 	"github.com/cloudwego/hertz/pkg/protocol"
diff --git a/pkg/app/server/binding/default.go b/pkg/app/server/binding/default.go
index 7e09ac9..42f55ee 100644
--- a/pkg/app/server/binding/default.go
+++ b/pkg/app/server/binding/default.go
@@ -70,8 +70,8 @@ import (
 	"strings"
 	"sync"
 
-	exprValidator "github.com/bytedance/go-tagexpr/v2/validator"
 	"github.com/cloudwego/hertz/internal/bytesconv"
+	exprValidator "github.com/cloudwego/hertz/internal/tagexpr/validator"
 	inDecoder "github.com/cloudwego/hertz/pkg/app/server/binding/internal/decoder"
 	hJson "github.com/cloudwego/hertz/pkg/common/json"
 	"github.com/cloudwego/hertz/pkg/common/utils"


Test patch:
diff --git a/internal/tagexpr/example_test.go b/internal/tagexpr/example_test.go
new file mode 100644
index 0000000..fab5e87
--- /dev/null
+++ b/internal/tagexpr/example_test.go
@@ -0,0 +1,80 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr_test
+
+import (
+	"fmt"
+
+	"github.com/cloudwego/hertz/internal/tagexpr"
+)
+
+func Example() {
+	type T struct {
+		A  int             `tagexpr:"$<0||$>=100"`
+		B  string          `tagexpr:"len($)>1 && regexp('^\\w*$')"`
+		C  bool            `tagexpr:"expr1:(f.g)$>0 && $; expr2:'C must be true when T.f.g>0'"`
+		d  []string        `tagexpr:"@:len($)>0 && $[0]=='D'; msg:sprintf('invalid d: %v',$)"`
+		e  map[string]int  `tagexpr:"len($)==$['len']"`
+		e2 map[string]*int `tagexpr:"len($)==$['len']"`
+		f  struct {
+			g int `tagexpr:"$"`
+		}
+		h int `tagexpr:"$>minVal"`
+	}
+
+	vm := tagexpr.New("tagexpr")
+	t := &T{
+		A:  107,
+		B:  "abc",
+		C:  true,
+		d:  []string{"x", "y"},
+		e:  map[string]int{"len": 1},
+		e2: map[string]*int{"len": new(int)},
+		f: struct {
+			g int `tagexpr:"$"`
+		}{1},
+		h: 10,
+	}
+
+	tagExpr, err := vm.Run(t)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(tagExpr.Eval("A"))
+	fmt.Println(tagExpr.Eval("B"))
+	fmt.Println(tagExpr.Eval("C@expr1"))
+	fmt.Println(tagExpr.Eval("C@expr2"))
+	if !tagExpr.Eval("d").(bool) {
+		fmt.Println(tagExpr.Eval("d@msg"))
+	}
+	fmt.Println(tagExpr.Eval("e"))
+	fmt.Println(tagExpr.Eval("e2"))
+	fmt.Println(tagExpr.Eval("f.g"))
+	fmt.Println(tagExpr.EvalWithEnv("h", map[string]interface{}{"minVal": 9}))
+	fmt.Println(tagExpr.EvalWithEnv("h", map[string]interface{}{"minVal": 11}))
+
+	// Output:
+	// true
+	// true
+	// true
+	// C must be true when T.f.g>0
+	// invalid d: [x y]
+	// true
+	// false
+	// 1
+	// true
+	// false
+}
diff --git a/internal/tagexpr/expr_test.go b/internal/tagexpr/expr_test.go
new file mode 100644
index 0000000..bec8241
--- /dev/null
+++ b/internal/tagexpr/expr_test.go
@@ -0,0 +1,248 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"math"
+	"reflect"
+	"testing"
+)
+
+func TestExpr(t *testing.T) {
+	cases := []struct {
+		expr string
+		val  interface{}
+	}{
+		// Simple string
+		{expr: "'a'", val: "a"},
+		{expr: "('a')", val: "a"},
+		// Simple digital
+		{expr: " 10 ", val: 10.0},
+		{expr: "(10)", val: 10.0},
+		// Simple bool
+		{expr: "true", val: true},
+		{expr: "!true", val: false},
+		{expr: "!!true", val: true},
+		{expr: "false", val: false},
+		{expr: "!false", val: true},
+		{expr: "!!false", val: false},
+		{expr: "(false)", val: false},
+		{expr: "(!false)", val: true},
+		{expr: "(!!false)", val: false},
+		{expr: "!!(!false)", val: true},
+		{expr: "!(!false)", val: false},
+		// Join string
+		{expr: "'true '+('a')", val: "true a"},
+		{expr: "'a'+('b'+'c')+'d'", val: "abcd"},
+		// Arithmetic operator
+		{expr: "1+7+2", val: 10.0},
+		{expr: "1+(7)+(2)", val: 10.0},
+		{expr: "1.1+ 2", val: 3.1},
+		{expr: "-1.1+4", val: 2.9},
+		{expr: "10-7-2", val: 1.0},
+		{expr: "20/2", val: 10.0},
+		{expr: "1/0", val: math.NaN()},
+		{expr: "20%2", val: 0.0},
+		{expr: "6 % 5", val: 1.0},
+		{expr: "20%7 %5", val: 1.0},
+		{expr: "1*2+7+2.2", val: 11.2},
+		{expr: "-20/2+1+2", val: -7.0},
+		{expr: "20/2+1-2-1", val: 8.0},
+		{expr: "30/(2+1)/5-2-1", val: -1.0},
+		{expr: "100/(( 2+8)*5 )-(1 +1- 0)", val: 0.0},
+		{expr: "(2*3)+(4*2)", val: 14.0},
+		{expr: "1+(2*(3+4))", val: 15.0},
+		{expr: "20%(7%5)", val: 0.0},
+		// Relational operator
+		{expr: "50 == 5", val: false},
+		{expr: "'50'==50", val: true},
+		{expr: "'50'=='50'", val: true},
+		{expr: "'50' =='5' == true", val: false},
+		{expr: "50== 50 == false", val: false},
+		{expr: "50== 50 == true ==true==true", val: true},
+		{expr: "50 != 5", val: true},
+		{expr: "'50'!=50", val: false},
+		{expr: "'50'!= '50'", val: false},
+		{expr: "'50' !='5' != true", val: false},
+		{expr: "50!= 50 == false", val: true},
+		{expr: "50== 50 != true ==true!=true", val: true},
+		{expr: "50 > 5", val: true},
+		{expr: "50.1 > 50.1", val: false},
+		{expr: "3.2 > 2.1", val: true},
+		{expr: "'3.2' > '2.1'", val: true},
+		{expr: "'13.2'>'2.1'", val: false},
+		{expr: "3.2 >= 2.1", val: true},
+		{expr: "2.1 >= 2.1", val: true},
+		{expr: "2.05 >= 2.1", val: false},
+		{expr: "'2.05'>='2.1'", val: false},
+		{expr: "'12.05'>='2.1'", val: false},
+		{expr: "50 < 5", val: false},
+		{expr: "50.1 < 50.1", val: false},
+		{expr: "3 <12.11", val: true},
+		{expr: "3.2 < 2.1", val: false},
+		{expr: "'3.2' < '2.1'", val: false},
+		{expr: "'13.2' < '2.1'", val: true},
+		{expr: "3.2 <= 2.1", val: false},
+		{expr: "2.1 <= 2.1", val: true},
+		{expr: "2.05 <= 2.1", val: true},
+		{expr: "'2.05'<='2.1'", val: true},
+		{expr: "'12.05'<='2.1'", val: true},
+		// Logical operator
+		{expr: "!('13.2' < '2.1')", val: false},
+		{expr: "(3.2 <= 2.1) &&true", val: false},
+		{expr: "true&&(2.1<=2.1)", val: true},
+		{expr: "(2.05<=2.1)&&false", val: false},
+		{expr: "true&&!true&&false", val: false},
+		{expr: "true&&true&&true", val: true},
+		{expr: "true&&true&&false", val: false},
+		{expr: "false&&true&&true", val: false},
+		{expr: "true && false && true", val: false},
+		{expr: "true||false", val: true},
+		{expr: "false ||true", val: true},
+		{expr: "true&&true || false", val: true},
+		{expr: "true&&false || false", val: false},
+		{expr: "true && false || true ", val: true},
+	}
+	for _, c := range cases {
+		t.Log(c.expr)
+		vm, err := parseExpr(c.expr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		val := vm.run("", nil)
+		if !reflect.DeepEqual(val, c.val) {
+			if f, ok := c.val.(float64); ok && math.IsNaN(f) && math.IsNaN(val.(float64)) {
+				continue
+			}
+			t.Fatalf("expr: %q, got: %v, expect: %v", c.expr, val, c.val)
+		}
+	}
+}
+
+func TestExprWithEnv(t *testing.T) {
+	cases := []struct {
+		expr string
+		val  interface{}
+	}{
+		// env: a = 10, b = "string value",
+		{expr: "a", val: 10.0},
+		{expr: "b", val: "string value"},
+		{expr: "a>10", val: false},
+		{expr: "a<11", val: true},
+		{expr: "a+1", val: 11.0},
+		{expr: "a==10", val: true},
+	}
+
+	for _, c := range cases {
+		t.Log(c.expr)
+		vm, err := parseExpr(c.expr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		val := vm.runWithEnv("", nil, map[string]interface{}{"a": 10, "b": "string value"})
+		if !reflect.DeepEqual(val, c.val) {
+			if f, ok := c.val.(float64); ok && math.IsNaN(f) && math.IsNaN(val.(float64)) {
+				continue
+			}
+			t.Fatalf("expr: %q, got: %v, expect: %v", c.expr, val, c.val)
+		}
+	}
+}
+
+func TestPriority(t *testing.T) {
+	cases := []struct {
+		expr string
+		val  interface{}
+	}{
+		{expr: "false||true&&8==8", val: true},
+		{expr: "1+2>5-4", val: true},
+		{expr: "1+2*4/2", val: 5.0},
+		{expr: "(true||false)&&false||false", val: false},
+		{expr: "true||false&&false||false", val: true},
+		{expr: "true||1<0&&'a'!='a'||0!=0", val: true},
+	}
+	for _, c := range cases {
+		t.Log(c.expr)
+		vm, err := parseExpr(c.expr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		val := vm.run("", nil)
+		if !reflect.DeepEqual(val, c.val) {
+			if f, ok := c.val.(float64); ok && math.IsNaN(f) && math.IsNaN(val.(float64)) {
+				continue
+			}
+			t.Fatalf("expr: %q, got: %v, expect: %v", c.expr, val, c.val)
+		}
+	}
+}
+
+func TestBuiltInFunc(t *testing.T) {
+	cases := []struct {
+		expr string
+		val  interface{}
+	}{
+		{expr: "len('abc')", val: 3.0},
+		{expr: "len('abc')+2*2/len('cd')", val: 5.0},
+		{expr: "len(0)", val: 0.0},
+
+		{expr: "regexp('a\\d','a0')", val: true},
+		{expr: "regexp('^a\\d$','a0')", val: true},
+		{expr: "regexp('a\\d','a')", val: false},
+		{expr: "regexp('^a\\d$','a')", val: false},
+
+		{expr: "sprintf('test string: %s','a')", val: "test string: a"},
+		{expr: "sprintf('test string: %s','a'+'b')", val: "test string: ab"},
+		{expr: "sprintf('test string: %s,%v','a',1)", val: "test string: a,1"},
+		{expr: "sprintf('')+'a'", val: "a"},
+		{expr: "sprintf('%v',10+2*2)", val: "14"},
+	}
+	for _, c := range cases {
+		t.Log(c.expr)
+		vm, err := parseExpr(c.expr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		val := vm.run("", nil)
+		if !reflect.DeepEqual(val, c.val) {
+			if f, ok := c.val.(float64); ok && math.IsNaN(f) && math.IsNaN(val.(float64)) {
+				continue
+			}
+			t.Fatalf("expr: %q, got: %v, expect: %v", c.expr, val, c.val)
+		}
+	}
+}
+
+func TestSyntaxIncorrect(t *testing.T) {
+	cases := []struct {
+		incorrectExpr string
+	}{
+		{incorrectExpr: "1 + + 'a'"},
+		{incorrectExpr: "regexp()"},
+		{incorrectExpr: "regexp('^'+'a','a')"},
+		{incorrectExpr: "regexp('^a','a','b')"},
+		{incorrectExpr: "sprintf()"},
+		{incorrectExpr: "sprintf(0)"},
+		{incorrectExpr: "sprintf('a'+'b')"},
+	}
+	for _, c := range cases {
+		_, err := parseExpr(c.incorrectExpr)
+		if err == nil {
+			t.Fatalf("expect syntax incorrect: %s", c.incorrectExpr)
+		} else {
+			t.Log(err)
+		}
+	}
+}
diff --git a/internal/tagexpr/selector_test.go b/internal/tagexpr/selector_test.go
new file mode 100644
index 0000000..bfb5dd4
--- /dev/null
+++ b/internal/tagexpr/selector_test.go
@@ -0,0 +1,30 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"testing"
+)
+
+func TestExprSelector(t *testing.T) {
+	es := ExprSelector("F1.Index")
+	field, ok := es.ParentField()
+	if !ok {
+		t.Fatal("not ok")
+	}
+	if "F1" != field {
+		t.Fatal(field)
+	}
+}
diff --git a/internal/tagexpr/spec_func_test.go b/internal/tagexpr/spec_func_test.go
new file mode 100644
index 0000000..3d66a49
--- /dev/null
+++ b/internal/tagexpr/spec_func_test.go
@@ -0,0 +1,104 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr_test
+
+import (
+	"reflect"
+	"regexp"
+	"testing"
+
+	"github.com/cloudwego/hertz/internal/tagexpr"
+)
+
+func TestFunc(t *testing.T) {
+	emailRegexp := regexp.MustCompile(
+		"^([A-Za-z0-9_\\-\\.\u4e00-\u9fa5])+\\@([A-Za-z0-9_\\-\\.])+\\.([A-Za-z]{2,8})$",
+	)
+	tagexpr.RegFunc("email", func(args ...interface{}) interface{} {
+		if len(args) == 0 {
+			return false
+		}
+		s, ok := args[0].(string)
+		if !ok {
+			return false
+		}
+		t.Log(s)
+		return emailRegexp.MatchString(s)
+	})
+
+	vm := tagexpr.New("te")
+
+	type T struct {
+		Email string `te:"email($)"`
+	}
+	cases := []struct {
+		email  string
+		expect bool
+	}{
+		{"", false},
+		{"henrylee2cn@gmail.com", true},
+	}
+
+	obj := new(T)
+	for _, c := range cases {
+		obj.Email = c.email
+		te := vm.MustRun(obj)
+		got := te.EvalBool("Email")
+		if got != c.expect {
+			t.Fatalf("email: %s, expect: %v, but got: %v", c.email, c.expect, got)
+		}
+	}
+
+	// test len
+	type R struct {
+		Str string `vd:"mblen($)<6"`
+	}
+	lenCases := []struct {
+		str    string
+		expect bool
+	}{
+		{"123", true},
+		{"一二三四五六七", false},
+		{"一二三四五", true},
+	}
+
+	lenObj := new(R)
+	vm = tagexpr.New("vd")
+	for _, lenCase := range lenCases {
+		lenObj.Str = lenCase.str
+		te := vm.MustRun(lenObj)
+		got := te.EvalBool("Str")
+		if got != lenCase.expect {
+			t.Fatalf("string: %v, expect: %v, but got: %v", lenCase.str, lenCase.expect, got)
+		}
+	}
+}
+
+func TestRangeIn(t *testing.T) {
+	vm := tagexpr.New("te")
+	type S struct {
+		F []string `te:"range($, in(#v, '', 'ttp', 'euttp'))"`
+	}
+	a := []string{"ttp", "", "euttp"}
+	r := vm.MustRun(S{
+		F: a,
+		// F: b,
+	})
+	expect := []interface{}{true, true, true}
+	actual := r.Eval("F")
+	if !reflect.DeepEqual(expect, actual) {
+		t.Fatal("not equal", expect, actual)
+	}
+}
diff --git a/internal/tagexpr/spec_range_test.go b/internal/tagexpr/spec_range_test.go
new file mode 100644
index 0000000..bc4f73a
--- /dev/null
+++ b/internal/tagexpr/spec_range_test.go
@@ -0,0 +1,54 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/cloudwego/hertz/internal/tagexpr"
+)
+
+func TestIssue12(t *testing.T) {
+	vm := tagexpr.New("te")
+	type I int
+	type S struct {
+		F    []I              `te:"range($, '>'+sprintf('%v:%v', #k, #v+2+len($)))"`
+		Fs   [][]I            `te:"range($, range(#v, '>'+sprintf('%v:%v', #k, #v+2+##)))"`
+		M    map[string]I     `te:"range($, '>'+sprintf('%s:%v', #k, #v+2+##))"`
+		MFs  []map[string][]I `te:"range($, range(#v, range(#v, '>'+sprintf('%v:%v', #k, #v+2+##))))"`
+		MFs2 []map[string][]I `te:"range($, range(#v, range(#v, '>'+sprintf('%v:%v', #k, #v+2+##))))"`
+	}
+	a := []I{2, 3}
+	r := vm.MustRun(S{
+		F:    a,
+		Fs:   [][]I{a},
+		M:    map[string]I{"m0": 2, "m1": 3},
+		MFs:  []map[string][]I{{"m": a}},
+		MFs2: []map[string][]I{},
+	})
+	assertEqual(t, []interface{}{">0:6", ">1:7"}, r.Eval("F"))
+	assertEqual(t, []interface{}{[]interface{}{">0:6", ">1:7"}}, r.Eval("Fs"))
+	assertEqual(t, []interface{}{[]interface{}{[]interface{}{">0:6", ">1:7"}}}, r.Eval("MFs"))
+	assertEqual(t, []interface{}{}, r.Eval("MFs2"))
+	assertEqual(t, true, r.EvalBool("MFs2"))
+
+	// result may not stable for map
+	got := r.Eval("M")
+	if !reflect.DeepEqual([]interface{}{">m0:6", ">m1:7"}, got) &&
+		!reflect.DeepEqual([]interface{}{">m1:7", ">m0:6"}, got) {
+		t.Fatal(got)
+	}
+}
diff --git a/internal/tagexpr/spec_test.go b/internal/tagexpr/spec_test.go
new file mode 100644
index 0000000..07f93d1
--- /dev/null
+++ b/internal/tagexpr/spec_test.go
@@ -0,0 +1,162 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"context"
+	"reflect"
+	"testing"
+)
+
+func TestReadPairedSymbol(t *testing.T) {
+	cases := []struct {
+		left, right             rune
+		expr, val, lastExprNode string
+	}{
+		{left: '\'', right: '\'', expr: "'true '+'a'", val: "true ", lastExprNode: "+'a'"},
+		{left: '(', right: ')', expr: "((0+1)/(2-1)*9)%2", val: "(0+1)/(2-1)*9", lastExprNode: "%2"},
+		{left: '(', right: ')', expr: `(\)\(\))`, val: `)()`},
+		{left: '\'', right: '\'', expr: `'\\'`, val: `\\`},
+		{left: '\'', right: '\'', expr: `'\'\''`, val: `''`},
+	}
+	for _, c := range cases {
+		t.Log(c.expr)
+		expr := c.expr
+		got := readPairedSymbol(&expr, c.left, c.right)
+		if got == nil {
+			t.Fatalf("expr: %q, got: %v, %q, want: %q, %q", c.expr, got, expr, c.val, c.lastExprNode)
+		} else if *got != c.val || expr != c.lastExprNode {
+			t.Fatalf("expr: %q, got: %q, %q, want: %q, %q", c.expr, *got, expr, c.val, c.lastExprNode)
+		}
+	}
+}
+
+func TestReadBoolExprNode(t *testing.T) {
+	cases := []struct {
+		expr         string
+		val          bool
+		lastExprNode string
+	}{
+		{expr: "false", val: false, lastExprNode: ""},
+		{expr: "true", val: true, lastExprNode: ""},
+		{expr: "true ", val: true, lastExprNode: " "},
+		{expr: "!true&", val: false, lastExprNode: "&"},
+		{expr: "!false|", val: true, lastExprNode: "|"},
+		{expr: "!!!!false =", val: !!!!false, lastExprNode: " ="},
+	}
+	for _, c := range cases {
+		t.Log(c.expr)
+		expr := c.expr
+		e := readBoolExprNode(&expr)
+		got := e.Run(context.TODO(), "", nil).(bool)
+		if got != c.val || expr != c.lastExprNode {
+			t.Fatalf("expr: %s, got: %v, %s, want: %v, %s", c.expr, got, expr, c.val, c.lastExprNode)
+		}
+	}
+}
+
+func TestReadDigitalExprNode(t *testing.T) {
+	cases := []struct {
+		expr         string
+		val          float64
+		lastExprNode string
+	}{
+		{expr: "0.1 +1", val: 0.1, lastExprNode: " +1"},
+		{expr: "-1\\1", val: -1, lastExprNode: "\\1"},
+		{expr: "1a", val: 0, lastExprNode: ""},
+		{expr: "1", val: 1, lastExprNode: ""},
+		{expr: "1.1", val: 1.1, lastExprNode: ""},
+		{expr: "1.1/", val: 1.1, lastExprNode: "/"},
+	}
+	for _, c := range cases {
+		expr := c.expr
+		e := readDigitalExprNode(&expr)
+		if c.expr == "1a" {
+			if e != nil {
+				t.Fatalf("expr: %s, got:%v, want:%v", c.expr, e.Run(context.TODO(), "", nil), nil)
+			}
+			continue
+		}
+		got := e.Run(context.TODO(), "", nil).(float64)
+		if got != c.val || expr != c.lastExprNode {
+			t.Fatalf("expr: %s, got: %f, %s, want: %f, %s", c.expr, got, expr, c.val, c.lastExprNode)
+		}
+	}
+}
+
+func TestFindSelector(t *testing.T) {
+	cases := []struct {
+		expr         string
+		field        string
+		name         string
+		subSelector  []string
+		boolOpposite bool
+		signOpposite bool
+		found        bool
+		last         string
+	}{
+		{expr: "$", name: "$", found: true},
+		{expr: "!!$", name: "$", found: true},
+		{expr: "!$", name: "$", boolOpposite: true, found: true},
+		{expr: "+$", name: "$", found: true},
+		{expr: "--$", name: "$", found: true},
+		{expr: "-$", name: "$", signOpposite: true, found: true},
+		{expr: "---$", name: "$", signOpposite: true, found: true},
+		{expr: "()$", last: "()$"},
+		{expr: "(0)$", last: "(0)$"},
+		{expr: "(A)$", field: "A", name: "$", found: true},
+		{expr: "+(A)$", field: "A", name: "$", found: true},
+		{expr: "++(A)$", field: "A", name: "$", found: true},
+		{expr: "!(A)$", field: "A", name: "$", boolOpposite: true, found: true},
+		{expr: "-(A)$", field: "A", name: "$", signOpposite: true, found: true},
+		{expr: "(A0)$", field: "A0", name: "$", found: true},
+		{expr: "!!(A0)$", field: "A0", name: "$", found: true},
+		{expr: "--(A0)$", field: "A0", name: "$", found: true},
+		{expr: "(A0)$(A1)$", last: "(A0)$(A1)$"},
+		{expr: "(A0)$ $(A1)$", field: "A0", name: "$", found: true, last: " $(A1)$"},
+		{expr: "$a", last: "$a"},
+		{expr: "$[1]['a']", name: "$", subSelector: []string{"1", "'a'"}, found: true},
+		{expr: "$[1][]", last: "$[1][]"},
+		{expr: "$[[]]", last: "$[[]]"},
+		{expr: "$[[[]]]", last: "$[[[]]]"},
+		{expr: "$[(A)$[1]]", name: "$", subSelector: []string{"(A)$[1]"}, found: true},
+		{expr: "$>0&&$<10", name: "$", found: true, last: ">0&&$<10"},
+	}
+	for _, c := range cases {
+		last := c.expr
+		field, name, subSelector, boolOpposite, signOpposite, found := findSelector(&last)
+		if found != c.found {
+			t.Fatalf("%q found: got: %v, want: %v", c.expr, found, c.found)
+		}
+		if c.boolOpposite && (boolOpposite == nil || !*boolOpposite) {
+			t.Fatalf("%q boolOpposite: got: %v, want: %v", c.expr, boolOpposite, c.boolOpposite)
+		}
+		if c.signOpposite && (signOpposite == nil || !*signOpposite) {
+			t.Fatalf("%q signOpposite: got: %v, want: %v", c.expr, signOpposite, c.signOpposite)
+		}
+		if field != c.field {
+			t.Fatalf("%q field: got: %q, want: %q", c.expr, field, c.field)
+		}
+		if name != c.name {
+			t.Fatalf("%q name: got: %q, want: %q", c.expr, name, c.name)
+		}
+		if !reflect.DeepEqual(subSelector, c.subSelector) {
+			t.Fatalf("%q subSelector: got: %v, want: %v", c.expr, subSelector, c.subSelector)
+		}
+		if last != c.last {
+			t.Fatalf("%q last: got: %q, want: %q", c.expr, last, c.last)
+		}
+	}
+}
diff --git a/internal/tagexpr/tagexpr_test.go b/internal/tagexpr/tagexpr_test.go
new file mode 100644
index 0000000..d571c41
--- /dev/null
+++ b/internal/tagexpr/tagexpr_test.go
@@ -0,0 +1,855 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr_test
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/cloudwego/hertz/internal/tagexpr"
+)
+
+func assertEqual(t *testing.T, v1, v2 interface{}, msgs ...interface{}) {
+	t.Helper()
+	if reflect.DeepEqual(v1, v2) {
+		return
+	}
+	t.Fatal(fmt.Sprintf("not equal %v %v", v1, v2) + "\n" + fmt.Sprint(msgs...))
+}
+
+func BenchmarkTagExpr(b *testing.B) {
+	type T struct {
+		a int `bench:"$%3"`
+	}
+	vm := tagexpr.New("bench")
+	vm.MustRun(new(T)) // warm up
+	b.ReportAllocs()
+	b.ResetTimer()
+	t := &T{10}
+	for i := 0; i < b.N; i++ {
+		tagExpr, err := vm.Run(t)
+		if err != nil {
+			b.FailNow()
+		}
+		if tagExpr.EvalFloat("a") != 1 {
+			b.FailNow()
+		}
+	}
+}
+
+func BenchmarkReflect(b *testing.B) {
+	type T struct {
+		a int `remainder:"3"`
+	}
+	b.ReportAllocs()
+	b.ResetTimer()
+	t := &T{1}
+	for i := 0; i < b.N; i++ {
+		v := reflect.ValueOf(t).Elem()
+		ft, ok := v.Type().FieldByName("a")
+		if !ok {
+			b.FailNow()
+		}
+		x, err := strconv.ParseInt(ft.Tag.Get("remainder"), 10, 64)
+		if err != nil {
+			b.FailNow()
+		}
+		fv := v.FieldByName("a")
+		if fv.Int()%x != 1 {
+			b.FailNow()
+		}
+	}
+}
+
+func Test(t *testing.T) {
+	g := &struct {
+		_ int
+		h string `tagexpr:"$"`
+		s []string
+		m map[string][]string
+	}{
+		h: "haha",
+		s: []string{"1"},
+		m: map[string][]string{"0": {"2"}},
+	}
+	d := "ddd"
+	e := new(int)
+	*e = 3
+	type iface interface{}
+	cases := []struct {
+		tagName   string
+		structure interface{}
+		tests     map[string]interface{}
+	}{
+		{
+			tagName: "tagexpr",
+			structure: &struct {
+				A     int              `tagexpr:"$>0&&$<10&&!''&&!!!0&&!nil&&$"`
+				A2    int              `tagexpr:"@:$>0&&$<10"`
+				b     string           `tagexpr:"is:$=='test';msg:sprintf('expect: test, but got: %s',$)"`
+				c     float32          `tagexpr:"(A)$+$"`
+				d     *string          `tagexpr:"$"`
+				e     **int            `tagexpr:"$"`
+				f     *[3]int          `tagexpr:"x:len($)"`
+				g     string           `tagexpr:"x:!regexp('xxx',$);y:regexp('g\\d{3}$')"`
+				h     []string         `tagexpr:"x:$[1];y:$[10]"`
+				i     map[string]int   `tagexpr:"x:$['a'];y:$[0];z:$==nil"`
+				i2    *map[string]int  `tagexpr:"x:$['a'];y:$[0];z:$"`
+				j, j2 iface            `tagexpr:"@:$==1;y:$"`
+				k     *iface           `tagexpr:"$==nil"`
+				m     *struct{ i int } `tagexpr:"@:$;x:$['a']['x']"`
+			}{
+				A:  5.0,
+				A2: 5.0,
+				b:  "x",
+				c:  1,
+				d:  &d,
+				e:  &e,
+				f:  new([3]int),
+				g:  "g123",
+				h:  []string{"", "hehe"},
+				i:  map[string]int{"a": 7},
+				j2: iface(1),
+				m:  &struct{ i int }{1},
+			},
+			tests: map[string]interface{}{
+				"A":     true,
+				"A2":    true,
+				"b@is":  false,
+				"b@msg": "expect: test, but got: x",
+				"c":     6.0,
+				"d":     d,
+				"e":     float64(*e),
+				"f@x":   float64(3),
+				"g@x":   true,
+				"g@y":   true,
+				"h@x":   "hehe",
+				"h@y":   nil,
+				"i@x":   7.0,
+				"i@y":   nil,
+				"i@z":   false,
+				"i2@x":  nil,
+				"i2@y":  nil,
+				"i2@z":  nil,
+				"j":     false,
+				"j@y":   nil,
+				"j2":    true,
+				"j2@y":  1.0,
+				"k":     true,
+				"m":     &struct{ i int }{1},
+				"m@x":   nil,
+			},
+		},
+		{
+			tagName: "tagexpr",
+			structure: &struct {
+				A int    `tagexpr:"$>0&&$<10"`
+				b string `tagexpr:"is:$=='test';msg:sprintf('expect: test, but got: %s',$)"`
+				c struct {
+					_ int
+					d bool `tagexpr:"$"`
+				}
+				e *struct {
+					_ int
+					f bool `tagexpr:"$"`
+				}
+				g **struct {
+					_ int
+					h string `tagexpr:"$"`
+					s []string
+					m map[string][]string
+				} `tagexpr:"$['h']"`
+				i string  `tagexpr:"(g.s)$[0]+(g.m)$['0'][0]==$"`
+				j bool    `tagexpr:"!$"`
+				k int     `tagexpr:"!$"`
+				m *int    `tagexpr:"$==nil"`
+				n *bool   `tagexpr:"$==nil"`
+				p *string `tagexpr:"$"`
+			}{
+				A: 5,
+				b: "x",
+				c: struct {
+					_ int
+					d bool `tagexpr:"$"`
+				}{d: true},
+				e: &struct {
+					_ int
+					f bool `tagexpr:"$"`
+				}{f: true},
+				g: &g,
+				i: "12",
+			},
+			tests: map[string]interface{}{
+				"A":     true,
+				"b@is":  false,
+				"b@msg": "expect: test, but got: x",
+				"c.d":   true,
+				"e.f":   true,
+				"g":     "haha",
+				"g.h":   "haha",
+				"i":     true,
+				"j":     true,
+				"k":     true,
+				"m":     true,
+				"n":     true,
+				"p":     nil,
+			},
+		},
+		{
+			tagName: "p",
+			structure: &struct {
+				q *struct {
+					x int
+				} `p:"(q.x)$"`
+			}{},
+			tests: map[string]interface{}{
+				"q": nil,
+			},
+		},
+	}
+	for i, c := range cases {
+		vm := tagexpr.New(c.tagName)
+		// vm.WarmUp(c.structure)
+		tagExpr, err := vm.Run(c.structure)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for selector, value := range c.tests {
+			val := tagExpr.Eval(selector)
+			if !reflect.DeepEqual(val, value) {
+				t.Fatalf("Eval Serial: %d, selector: %q, got: %v, expect: %v", i, selector, val, value)
+			}
+		}
+		tagExpr.Range(func(eh *tagexpr.ExprHandler) error {
+			es := eh.ExprSelector()
+			t.Logf("Range selector: %s, field: %q exprName: %q", es, es.Field(), es.Name())
+			value := c.tests[es.String()]
+			val := eh.Eval()
+			if !reflect.DeepEqual(val, value) {
+				t.Fatalf("Range NO: %d, selector: %q, got: %v, expect: %v", i, es, val, value)
+			}
+			return nil
+		})
+	}
+}
+
+func TestFieldNotInit(t *testing.T) {
+	g := &struct {
+		_ int
+		h string
+		s []string
+		m map[string][]string
+	}{
+		h: "haha",
+		s: []string{"1"},
+		m: map[string][]string{"0": {"2"}},
+	}
+	structure := &struct {
+		A int
+		b string
+		c struct {
+			_ int
+			d *bool `expr:"test:nil"`
+		}
+		e *struct {
+			_ int
+			f bool
+		}
+		g **struct {
+			_ int
+			h string
+			s []string
+			m map[string][]string
+		}
+		i string
+		j bool
+		k int
+		m *int
+		n *bool
+		p *string
+	}{
+		A: 5,
+		b: "x",
+		e: &struct {
+			_ int
+			f bool
+		}{f: true},
+		g: &g,
+		i: "12",
+	}
+	vm := tagexpr.New("expr")
+	e, err := vm.Run(structure)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cases := []struct {
+		fieldSelector string
+		value         interface{}
+	}{
+		{"A", structure.A},
+		{"b", structure.b},
+		{"c", structure.c},
+		{"c._", 0},
+		{"c.d", structure.c.d},
+		{"e", structure.e},
+		{"e._", 0},
+		{"e.f", structure.e.f},
+		{"g", structure.g},
+		{"g._", 0},
+		{"g.h", (*structure.g).h},
+		{"g.s", (*structure.g).s},
+		{"g.m", (*structure.g).m},
+		{"i", structure.i},
+		{"j", structure.j},
+		{"k", structure.k},
+		{"m", structure.m},
+		{"n", structure.n},
+		{"p", structure.p},
+	}
+	for _, c := range cases {
+		fh, _ := e.Field(c.fieldSelector)
+		val := fh.Value(false).Interface()
+		assertEqual(t, c.value, val, c.fieldSelector)
+	}
+	var i int
+	e.RangeFields(func(fh *tagexpr.FieldHandler) bool {
+		val := fh.Value(false).Interface()
+		if fh.StringSelector() == "c.d" {
+			if fh.EvalFuncs()["c.d@test"] == nil {
+				t.Fatal("nil")
+			}
+		}
+		assertEqual(t, cases[i].value, val, fh.StringSelector())
+		i++
+		return true
+	})
+	var wall uint64 = 1024
+	unix := time.Unix(1549186325, int64(wall))
+	e, err = vm.Run(&unix)
+	if err != nil {
+		t.Fatal(err)
+	}
+	fh, _ := e.Field("wall")
+	val := fh.Value(false).Interface()
+	if !reflect.DeepEqual(val, wall) {
+		t.Fatalf("Time.wall: got: %v(%[1]T), expect: %v(%[2]T)", val, wall)
+	}
+}
+
+func TestFieldInitZero(t *testing.T) {
+	g := &struct {
+		_ int
+		h string
+		s []string
+		m map[string][]string
+	}{
+		h: "haha",
+		s: []string{"1"},
+		m: map[string][]string{"0": {"2"}},
+	}
+
+	structure := &struct {
+		A int
+		b string
+		c struct {
+			_ int
+			d *bool
+		}
+		e *struct {
+			_ int
+			f bool
+		}
+		g **struct {
+			_ int
+			h string
+			s []string
+			m map[string][]string
+		}
+		g2 ****struct {
+			_ int
+			h string
+			s []string
+			m map[string][]string
+		}
+		i string
+		j bool
+		k int
+		m *int
+		n *bool
+		p *string
+	}{
+		A: 5,
+		b: "x",
+		e: &struct {
+			_ int
+			f bool
+		}{f: true},
+		g: &g,
+		i: "12",
+	}
+
+	vm := tagexpr.New("")
+	e, err := vm.Run(structure)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cases := []struct {
+		fieldSelector string
+		value         interface{}
+	}{
+		{"A", structure.A},
+		{"b", structure.b},
+		{"c", struct {
+			_ int
+			d *bool
+		}{}},
+		{"c._", 0},
+		{"c.d", new(bool)},
+		{"e", structure.e},
+		{"e._", 0},
+		{"e.f", structure.e.f},
+		{"g", structure.g},
+		{"g._", 0},
+		{"g.h", (*structure.g).h},
+		{"g.s", (*structure.g).s},
+		{"g.m", (*structure.g).m},
+		{"g2.m", (map[string][]string)(nil)},
+		{"i", structure.i},
+		{"j", structure.j},
+		{"k", structure.k},
+		{"m", new(int)},
+		{"n", new(bool)},
+		{"p", new(string)},
+	}
+	for _, c := range cases {
+		fh, _ := e.Field(c.fieldSelector)
+		val := fh.Value(true).Interface()
+		assertEqual(t, c.value, val, c.fieldSelector)
+	}
+}
+
+func TestOperator(t *testing.T) {
+	type Tmp1 struct {
+		A string `tagexpr:$=="1"||$=="2"||$="3"` //nolint:govet
+		B []int  `tagexpr:len($)>=10&&$[0]<10`   //nolint:govet
+		C interface{}
+	}
+
+	type Tmp2 struct {
+		A *Tmp1
+		B interface{}
+	}
+
+	type Target struct {
+		A int             `tagexpr:"-$+$<=10"`
+		B int             `tagexpr:"+$-$<=10"`
+		C int             `tagexpr:"-$+(M)$*(N)$/$%(D.B)$[2]+$==1"`
+		D *Tmp1           `tagexpr:"(D.A)$!=nil"`
+		E string          `tagexpr:"((D.A)$=='1'&&len($)>1)||((D.A)$=='2'&&len($)>2)||((D.A)$=='3'&&len($)>3)"`
+		F map[string]int  `tagexpr:"x:len($);y:$['a']>10&&$['b']>1"`
+		G *map[string]int `tagexpr:"x:$['a']+(F)$['a']>20"`
+		H []string        `tagexpr:"len($)>=1&&len($)<10&&$[0]=='123'&&$[1]!='456'"`
+		I interface{}     `tagexpr:"$!=nil"`
+		K *string         `tagexpr:"len((D.A)$)+len($)<10&&len((D.A)$+$)<10"`
+		L **string        `tagexpr:"false"`
+		M float64         `tagexpr:"$/2>10&&$%2==0"`
+		N *float64        `tagexpr:"($+$*$-$/$+1)/$==$+1"`
+		O *[3]float64     `tagexpr:"$[0]>10&&$[0]<20||$[0]>20&&$[0]<30"`
+		P *Tmp2           `tagexpr:"x:$!=nil;y:len((P.A.A)$)<=1&&(P.A.B)$[0]==1;z:$['A']['C']==nil;w:$['A']['B'][0]==1;r:$[0][1][2]==3;s1:$[2]==nil;s2:$[0][3]==nil;s3:(ZZ)$;s4:(P.B)$!=nil"`
+		Q *Tmp2           `tagexpr:"s1:$['A']['B']!=nil;s2:(Q.A)$['B']!=nil;s3:$['A']['C']==nil;s4:(Q.A)$['C']==nil;s5:(Q.A)$['B'][0]==1;s6:$['X']['Z']==nil"`
+	}
+
+	k := "123456"
+	n := float64(-12.5)
+	o := [3]float64{15, 9, 9}
+	cases := []struct {
+		tagName   string
+		structure interface{}
+		tests     map[string]interface{}
+	}{
+		{
+			tagName: "tagexpr",
+			structure: &Target{
+				A: 5,
+				B: 10,
+				C: -10,
+				D: &Tmp1{A: "3", B: []int{1, 2, 3}},
+				E: "1234",
+				F: map[string]int{"a": 11, "b": 9},
+				G: &map[string]int{"a": 11},
+				H: []string{"123", "45"},
+				I: struct{}{},
+				K: &k,
+				L: nil,
+				M: float64(30),
+				N: &n,
+				O: &o,
+				P: &Tmp2{A: &Tmp1{A: "3", B: []int{1, 2, 3}}, B: struct{}{}},
+				Q: &Tmp2{A: &Tmp1{A: "3", B: []int{1, 2, 3}}, B: struct{}{}},
+			},
+			tests: map[string]interface{}{
+				"A":   true,
+				"B":   true,
+				"C":   true,
+				"D":   true,
+				"E":   true,
+				"F@x": float64(2),
+				"F@y": true,
+				"G@x": true,
+				"H":   true,
+				"I":   true,
+				"K":   true,
+				"L":   false,
+				"M":   true,
+				"N":   true,
+				"O":   true,
+
+				"P@x":  true,
+				"P@y":  true,
+				"P@z":  true,
+				"P@w":  true,
+				"P@r":  true,
+				"P@s1": true,
+				"P@s2": true,
+				"P@s3": nil,
+				"P@s4": true,
+
+				"Q@s1": true,
+				"Q@s2": true,
+				"Q@s3": true,
+				"Q@s4": true,
+				"Q@s5": true,
+				"Q@s6": true,
+			},
+		},
+	}
+
+	for i, c := range cases {
+		vm := tagexpr.New(c.tagName)
+		// vm.WarmUp(c.structure)
+		tagExpr, err := vm.Run(c.structure)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for selector, value := range c.tests {
+			val := tagExpr.Eval(selector)
+			if !reflect.DeepEqual(val, value) {
+				t.Fatalf("Eval NO: %d, selector: %q, got: %v, expect: %v", i, selector, val, value)
+			}
+		}
+		tagExpr.Range(func(eh *tagexpr.ExprHandler) error {
+			es := eh.ExprSelector()
+			t.Logf("Range selector: %s, field: %q exprName: %q", es, es.Field(), es.Name())
+			value := c.tests[es.String()]
+			val := eh.Eval()
+			if !reflect.DeepEqual(val, value) {
+				t.Fatalf("Range NO: %d, selector: %q, got: %v, expect: %v", i, es, val, value)
+			}
+			return nil
+		})
+	}
+}
+
+func TestStruct(t *testing.T) {
+	type A struct {
+		B struct {
+			C struct {
+				D struct {
+					X string `vd:"$"`
+				}
+			} `vd:"@:$['D']['X']"`
+			C2 string `vd:"@:(C)$['D']['X']"`
+			C3 string `vd:"@:(C.D.X)$"`
+		}
+	}
+	a := new(A)
+	a.B.C.D.X = "xxx"
+	vm := tagexpr.New("vd")
+	expr := vm.MustRun(a)
+	assertEqual(t, "xxx", expr.EvalString("B.C2"))
+	assertEqual(t, "xxx", expr.EvalString("B.C3"))
+	assertEqual(t, "xxx", expr.EvalString("B.C"))
+	assertEqual(t, "xxx", expr.EvalString("B.C.D.X"))
+	expr.Range(func(eh *tagexpr.ExprHandler) error {
+		es := eh.ExprSelector()
+		t.Logf("Range selector: %s, field: %q exprName: %q", es, es.Field(), es.Name())
+		if eh.Eval().(string) != "xxx" {
+			t.FailNow()
+		}
+		return nil
+	})
+}
+
+func TestStruct2(t *testing.T) {
+	type IframeBlock struct {
+		XBlock struct {
+			BlockType string `vd:"$"`
+		}
+		Props struct {
+			Data struct {
+				DataType string `vd:"$"`
+			}
+		}
+	}
+	b := new(IframeBlock)
+	b.XBlock.BlockType = "BlockType"
+	b.Props.Data.DataType = "DataType"
+	vm := tagexpr.New("vd")
+	expr := vm.MustRun(b)
+	if expr.EvalString("XBlock.BlockType") != "BlockType" {
+		t.Fatal(expr.EvalString("XBlock.BlockType"))
+	}
+	if expr.EvalString("Props.Data.DataType") != "DataType" {
+		t.Fatal(expr.EvalString("Props.Data.DataType"))
+	}
+}
+
+func TestStruct3(t *testing.T) {
+	type Data struct {
+		DataType string `vd:"$"`
+	}
+	type Prop struct {
+		PropType string       `vd:"$"`
+		DD       []*Data      `vd:"$"`
+		DD2      []*Data      `vd:"$"`
+		DataMap  map[int]Data `vd:"$"`
+		DataMap2 map[int]Data `vd:"$"`
+	}
+	type IframeBlock struct {
+		XBlock struct {
+			BlockType string `vd:"$"`
+		}
+		Props    []Prop        `vd:"$"`
+		Props1   [2]Prop       `vd:"$"`
+		Props2   []Prop        `vd:"$"`
+		PropMap  map[int]*Prop `vd:"$"`
+		PropMap2 map[int]*Prop `vd:"$"`
+	}
+
+	b := new(IframeBlock)
+	b.XBlock.BlockType = "BlockType"
+	p1 := Prop{
+		PropType: "p1",
+		DD: []*Data{
+			{"p1s1"},
+			{"p1s2"},
+			nil,
+		},
+		DataMap: map[int]Data{
+			1: {"p1m1"},
+			2: {"p1m2"},
+			0: {},
+		},
+	}
+	b.Props = []Prop{p1}
+	p2 := &Prop{
+		PropType: "p2",
+		DD: []*Data{
+			{"p2s1"},
+			{"p2s2"},
+			nil,
+		},
+		DataMap: map[int]Data{
+			1: {"p2m1"},
+			2: {"p2m2"},
+			0: {},
+		},
+	}
+	b.Props1 = [2]Prop{p1, {}}
+	b.PropMap = map[int]*Prop{
+		9: p2,
+	}
+
+	vm := tagexpr.New("vd")
+	expr := vm.MustRun(b)
+	if expr.EvalString("XBlock.BlockType") != "BlockType" {
+		t.Fatal(expr.EvalString("XBlock.BlockType"))
+	}
+	err := expr.Range(func(eh *tagexpr.ExprHandler) error {
+		es := eh.ExprSelector()
+		t.Logf("Range selector: %s, field: %q exprName: %q, eval: %v", eh.Path(), es.Field(), es.Name(), eh.Eval())
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestNilField(t *testing.T) {
+	type P struct {
+		X **struct {
+			A *[]uint16 `tagexpr:"$"`
+		} `tagexpr:"$"`
+		Y **struct{} `tagexpr:"$"`
+	}
+	vm := tagexpr.New("tagexpr")
+	te := vm.MustRun(&P{})
+	te.Range(func(eh *tagexpr.ExprHandler) error {
+		r := eh.Eval()
+		if r != nil {
+			t.Fatal(eh.Path())
+		}
+		return nil
+	})
+
+	type G struct {
+		// Nil1 *int `tagexpr:"nil!=$"`
+		Nil2 *int `tagexpr:"$!=nil"`
+	}
+	g := &G{
+		// Nil1: new(int),
+		Nil2: new(int),
+	}
+	vm.MustRun(g).Range(func(eh *tagexpr.ExprHandler) error {
+		r, ok := eh.Eval().(bool)
+		if !ok || !r {
+			t.Fatal(eh.Path())
+		}
+		return nil
+	})
+}
+
+func TestDeepNested(t *testing.T) {
+	type testInner struct {
+		Address string `tagexpr:"name:$"`
+	}
+	type struct1 struct {
+		I *testInner
+		A []*testInner
+		X interface{}
+	}
+	type struct2 struct {
+		S *struct1
+	}
+	type Data struct {
+		S1 *struct2
+		S2 *struct2
+	}
+	data := &Data{
+		S1: &struct2{
+			S: &struct1{
+				I: &testInner{Address: "I:address"},
+				A: []*testInner{{Address: "A:address"}},
+				X: []*testInner{{Address: "X:address"}},
+			},
+		},
+		S2: &struct2{
+			S: &struct1{
+				A: []*testInner{nil},
+			},
+		},
+	}
+	expectKey := [...]interface{}{"S1.S.I.Address@name", "S2.S.I.Address@name", "S1.S.A[0].Address@name", "S2.S.A[0].Address@name", "S1.S.X[0].Address@name"}
+	expectValue := [...]interface{}{"I:address", nil, "A:address", nil, "X:address"}
+	var i int
+	vm := tagexpr.New("tagexpr")
+	vm.MustRun(data).Range(func(eh *tagexpr.ExprHandler) error {
+		assertEqual(t, expectKey[i], eh.Path())
+		assertEqual(t, expectValue[i], eh.Eval())
+		i++
+		t.Log(eh.Path(), eh.ExprSelector(), eh.Eval())
+		return nil
+	})
+	assertEqual(t, 5, i)
+}
+
+func TestIssue3(t *testing.T) {
+	type C struct {
+		Id    string
+		Index int32 `vd:"$"`
+		P     *int  `vd:"$!=nil"`
+	}
+	type A struct {
+		F1 *C
+		F2 *C
+	}
+	a := &A{
+		F1: &C{
+			Id:    "test",
+			Index: 1,
+			P:     new(int),
+		},
+	}
+	vm := tagexpr.New("vd")
+	err := vm.MustRun(a).Range(func(eh *tagexpr.ExprHandler) error {
+		switch eh.Path() {
+		case "F1.Index":
+			assertEqual(t, float64(1), eh.Eval(), eh.Path())
+		case "F2.Index":
+			assertEqual(t, nil, eh.Eval(), eh.Path())
+		case "F1.P":
+			assertEqual(t, true, eh.Eval(), eh.Path())
+		case "F2.P":
+			assertEqual(t, false, eh.Eval(), eh.Path())
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestIssue4(t *testing.T) {
+	type T struct {
+		A *string `te:"len($)+mblen($)"`
+		B *string `te:"len($)+mblen($)"`
+		C *string `te:"len($)+mblen($)"`
+	}
+	c := "c"
+	v := &T{
+		B: new(string),
+		C: &c,
+	}
+	vm := tagexpr.New("te")
+	err := vm.MustRun(v).Range(func(eh *tagexpr.ExprHandler) error {
+		t.Logf("eval:%v, path:%s", eh.EvalFloat(), eh.Path())
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestIssue5(t *testing.T) {
+	type A struct {
+		F1 int `vd:"true && $ <= 24*60*60"`        // 1500 ok
+		F2 int `vd:"$%60 == 0 && $ <= (24*60*60)"` // 1500 ok
+		F3 int `vd:"$ <= 24*60*60"`                // 1500 ok
+	}
+	a := &A{
+		F1: 1500,
+		F2: 1500,
+		F3: 1500,
+	}
+	vm := tagexpr.New("vd")
+	err := vm.MustRun(a).Range(func(eh *tagexpr.ExprHandler) error {
+		switch eh.Path() {
+		case "F1":
+			assertEqual(t, true, eh.Eval(), eh.Path())
+		case "F2":
+			assertEqual(t, true, eh.Eval(), eh.Path())
+		case "F3":
+			assertEqual(t, true, eh.Eval(), eh.Path())
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/internal/tagexpr/tagparser_test.go b/internal/tagexpr/tagparser_test.go
new file mode 100644
index 0000000..5f36fb8
--- /dev/null
+++ b/internal/tagexpr/tagparser_test.go
@@ -0,0 +1,93 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tagexpr
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestTagparser(t *testing.T) {
+	cases := []struct {
+		tag    reflect.StructTag
+		expect map[string]string
+		fail   bool
+	}{
+		{
+			tag: `tagexpr:"$>0"`,
+			expect: map[string]string{
+				"@": "$>0",
+			},
+		}, {
+			tag:  `tagexpr:"$>0;'xxx'"`,
+			fail: true,
+		}, {
+			tag: `tagexpr:"$>0;b:sprintf('%[1]T; %[1]v',(X)$)"`,
+			expect: map[string]string{
+				"@": `$>0`,
+				"b": `sprintf('%[1]T; %[1]v',(X)$)`,
+			},
+		}, {
+			tag: `tagexpr:"a:$=='0;1;';b:sprintf('%[1]T; %[1]v',(X)$)"`,
+			expect: map[string]string{
+				"a": `$=='0;1;'`,
+				"b": `sprintf('%[1]T; %[1]v',(X)$)`,
+			},
+		}, {
+			tag: `tagexpr:"a:1;;b:2"`,
+			expect: map[string]string{
+				"a": `1`,
+				"b": `2`,
+			},
+		}, {
+			tag: `tagexpr:";a:1;;b:2;;;"`,
+			expect: map[string]string{
+				"a": `1`,
+				"b": `2`,
+			},
+		}, {
+			tag: `tagexpr:";a:'123\\'';;b:'1\\'23';c:'1\\'2\\'3';;"`,
+			expect: map[string]string{
+				"a": `'123\''`,
+				"b": `'1\'23'`,
+				"c": `'1\'2\'3'`,
+			},
+		}, {
+			tag: `tagexpr:"email($)"`,
+			expect: map[string]string{
+				"@": `email($)`,
+			},
+		}, {
+			tag: `tagexpr:"false"`,
+			expect: map[string]string{
+				"@": `false`,
+			},
+		},
+	}
+
+	for _, c := range cases {
+		r, e := parseTag(c.tag.Get("tagexpr"))
+		if e != nil == c.fail {
+			if !reflect.DeepEqual(c.expect, r) {
+				t.Fatal(c.expect, r, c.tag)
+			}
+		} else {
+			t.Fatalf("tag:%s kvs:%v, err:%v", c.tag, r, e)
+		}
+		if e != nil {
+			t.Logf("tag:%q, errMsg:%v", c.tag, e)
+		}
+	}
+}
diff --git a/internal/tagexpr/validator/example_test.go b/internal/tagexpr/validator/example_test.go
new file mode 100644
index 0000000..0c17887
--- /dev/null
+++ b/internal/tagexpr/validator/example_test.go
@@ -0,0 +1,122 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validator_test
+
+import (
+	"fmt"
+
+	vd "github.com/cloudwego/hertz/internal/tagexpr/validator"
+)
+
+func Example() {
+	type InfoRequest struct {
+		Name         string   `vd:"($!='Alice'||(Age)$==18) && regexp('\\w')"`
+		Age          int      `vd:"$>0"`
+		Email        string   `vd:"email($)"`
+		Phone1       string   `vd:"phone($)"`
+		OtherPhones  []string `vd:"range($, phone(#v,'CN'))"`
+		*InfoRequest `vd:"?"`
+		Info1        *InfoRequest `vd:"?"`
+		Info2        *InfoRequest `vd:"-"`
+	}
+	info := &InfoRequest{
+		Name:        "Alice",
+		Age:         18,
+		Email:       "henrylee2cn@gmail.com",
+		Phone1:      "+8618812345678",
+		OtherPhones: []string{"18812345679", "18812345680"},
+	}
+	fmt.Println(vd.Validate(info))
+
+	type A struct {
+		A    int `vd:"$<0||$>=100"`
+		Info interface{}
+	}
+	info.Email = "xxx"
+	a := &A{A: 107, Info: info}
+	fmt.Println(vd.Validate(a))
+	type B struct {
+		B string `vd:"len($)>1 && regexp('^\\w*$')"`
+	}
+	b := &B{"abc"}
+	fmt.Println(vd.Validate(b) == nil)
+
+	type C struct {
+		C bool `vd:"@:(S.A)$>0 && !$; msg:'C must be false when S.A>0'"`
+		S *A
+	}
+	c := &C{C: true, S: a}
+	fmt.Println(vd.Validate(c))
+
+	type D struct {
+		d []string `vd:"@:len($)>0 && $[0]=='D'; msg:sprintf('invalid d: %v',$)"`
+	}
+	d := &D{d: []string{"x", "y"}}
+	fmt.Println(vd.Validate(d))
+
+	type E struct {
+		e map[string]int `vd:"len($)==$['len']"`
+	}
+	e := &E{map[string]int{"len": 2}}
+	fmt.Println(vd.Validate(e))
+
+	// Customizes the factory of validation error.
+	vd.SetErrorFactory(func(failPath, msg string) error {
+		return fmt.Errorf(`{"succ":false, "error":"validation failed: %s"}`, failPath)
+	})
+
+	type F struct {
+		f struct {
+			g int `vd:"$%3==0"`
+		}
+	}
+	f := &F{}
+	f.f.g = 10
+	fmt.Println(vd.Validate(f))
+
+	fmt.Println(vd.Validate(map[string]*F{"a": f}))
+	fmt.Println(vd.Validate(map[string]map[string]*F{"a": {"b": f}}))
+	fmt.Println(vd.Validate([]map[string]*F{{"a": f}}))
+	fmt.Println(vd.Validate(struct {
+		A []map[string]*F
+	}{A: []map[string]*F{{"x": f}}}))
+	fmt.Println(vd.Validate(map[*F]int{f: 1}))
+	fmt.Println(vd.Validate([][1]*F{{f}}))
+	fmt.Println(vd.Validate((*F)(nil)))
+	fmt.Println(vd.Validate(map[string]*F{}))
+	fmt.Println(vd.Validate(map[string]map[string]*F{}))
+	fmt.Println(vd.Validate([]map[string]*F{}))
+	fmt.Println(vd.Validate([]*F{}))
+
+	// Output:
+	// <nil>
+	// email format is incorrect
+	// true
+	// C must be false when S.A>0
+	// invalid d: [x y]
+	// invalid parameter: e
+	// {"succ":false, "error":"validation failed: f.g"}
+	// {"succ":false, "error":"validation failed: {v for k=a}.f.g"}
+	// {"succ":false, "error":"validation failed: {v for k=a}{v for k=b}.f.g"}
+	// {"succ":false, "error":"validation failed: [0]{v for k=a}.f.g"}
+	// {"succ":false, "error":"validation failed: A[0]{v for k=x}.f.g"}
+	// {"succ":false, "error":"validation failed: {k}.f.g"}
+	// {"succ":false, "error":"validation failed: [0][0].f.g"}
+	// unsupported data: nil
+	// <nil>
+	// <nil>
+	// <nil>
+	// <nil>
+}
diff --git a/internal/tagexpr/validator/validator_test.go b/internal/tagexpr/validator/validator_test.go
new file mode 100644
index 0000000..5cc2d7f
--- /dev/null
+++ b/internal/tagexpr/validator/validator_test.go
@@ -0,0 +1,354 @@
+// Copyright 2019 Bytedance Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validator_test
+
+import (
+	"encoding/json"
+	"errors"
+	"testing"
+
+	vd "github.com/cloudwego/hertz/internal/tagexpr/validator"
+)
+
+func assertEqualError(t *testing.T, err error, s string) {
+	t.Helper()
+	if err.Error() != s {
+		t.Fatal("not equal", err, s)
+	}
+}
+
+func assertNoError(t *testing.T, err error) {
+	t.Helper()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestNil(t *testing.T) {
+	type F struct {
+		F struct {
+			G int `vd:"$%3==1"`
+		}
+	}
+	assertEqualError(t, vd.Validate((*F)(nil)), "unsupported data: nil")
+}
+
+func TestAll(t *testing.T) {
+	type T struct {
+		A string `vd:"email($)"`
+		F struct {
+			G int `vd:"$%3==1"`
+		}
+	}
+	assertEqualError(t, vd.Validate(new(T), true), "email format is incorrect\tinvalid parameter: F.G")
+}
+
+func TestIssue1(t *testing.T) {
+	type MailBox struct {
+		Address *string `vd:"email($)"`
+		Name    *string
+	}
+	type EmailMsg struct {
+		Recipients       []*MailBox
+		RecipientsCc     []*MailBox
+		RecipientsBcc    []*MailBox
+		Subject          *string
+		Content          *string
+		AttachmentIDList []string
+		ReplyTo          *string
+		Params           map[string]string
+		FromEmailAddress *string
+		FromEmailName    *string
+	}
+	type EmailTaskInfo struct {
+		Msg         *EmailMsg
+		StartTimeMS *int64
+		LogTag      *string
+	}
+	type BatchCreateEmailTaskRequest struct {
+		InfoList []*EmailTaskInfo
+	}
+	invalid := "invalid email"
+	req := &BatchCreateEmailTaskRequest{
+		InfoList: []*EmailTaskInfo{
+			{
+				Msg: &EmailMsg{
+					Recipients: []*MailBox{
+						{
+							Address: &invalid,
+						},
+					},
+				},
+			},
+		},
+	}
+	assertEqualError(t, vd.Validate(req, false), "email format is incorrect")
+}
+
+func TestIssue2(t *testing.T) {
+	type a struct {
+		m map[string]interface{}
+	}
+	A := &a{
+		m: map[string]interface{}{
+			"1": 1,
+			"2": nil,
+		},
+	}
+	v := vd.New("vd")
+	assertNoError(t, v.Validate(A))
+}
+
+func TestIssue3(t *testing.T) {
+	type C struct {
+		Id    string
+		Index int32 `vd:"$==1"`
+	}
+	type A struct {
+		F1 *C
+		F2 *C
+	}
+	a := &A{
+		F1: &C{
+			Id:    "test",
+			Index: 1,
+		},
+	}
+	v := vd.New("vd")
+	assertNoError(t, v.Validate(a))
+}
+
+func TestIssue4(t *testing.T) {
+	type C struct {
+		Index  *int32 `vd:"@:$!=nil;msg:'index is nil'"`
+		Index2 *int32 `vd:"$!=nil"`
+		Index3 *int32 `vd:"$!=nil"`
+	}
+	type A struct {
+		F1 *C
+		F2 map[string]*C
+		F3 []*C
+	}
+	v := vd.New("vd")
+
+	a := &A{}
+	assertNoError(t, v.Validate(a))
+
+	a = &A{F1: new(C)}
+	assertEqualError(t, v.Validate(a), "index is nil")
+
+	a = &A{F2: map[string]*C{"x": {Index: new(int32)}}}
+	assertEqualError(t, v.Validate(a), "invalid parameter: F2{v for k=x}.Index2")
+
+	a = &A{F3: []*C{{Index: new(int32)}}}
+	assertEqualError(t, v.Validate(a), "invalid parameter: F3[0].Index2")
+
+	type B struct {
+		F1 *C `vd:"$!=nil"`
+		F2 *C
+	}
+	b := &B{}
+	assertEqualError(t, v.Validate(b), "invalid parameter: F1")
+
+	type D struct {
+		F1 *C
+		F2 *C
+	}
+
+	type E struct {
+		D []*D
+	}
+	b.F1 = new(C)
+	e := &E{D: []*D{nil}}
+	assertNoError(t, v.Validate(e))
+}
+
+func TestIssue5(t *testing.T) {
+	type SubSheet struct{}
+	type CopySheet struct {
+		Source      *SubSheet `json:"source" vd:"$!=nil"`
+		Destination *SubSheet `json:"destination" vd:"$!=nil"`
+	}
+	type UpdateSheetsRequest struct {
+		CopySheet *CopySheet `json:"copySheet"`
+	}
+	type BatchUpdateSheetRequestArg struct {
+		Requests []*UpdateSheetsRequest `json:"requests"`
+	}
+	b := `{"requests": [{}]}`
+	var data BatchUpdateSheetRequestArg
+	err := json.Unmarshal([]byte(b), &data)
+	assertNoError(t, err)
+	if len(data.Requests) != 1 {
+		t.Fatal(len(data.Requests))
+	}
+	if data.Requests[0].CopySheet != nil {
+		t.Fatal(data.Requests[0].CopySheet)
+	}
+	v := vd.New("vd")
+	assertNoError(t, v.Validate(&data))
+}
+
+func TestIn(t *testing.T) {
+	type S string
+	type I int16
+	type T struct {
+		X *int `vd:"$==nil || len($)>0"`
+		A S    `vd:"in($,'a','b','c')"`
+		B I    `vd:"in($,1,2.0,3)"`
+	}
+	v := vd.New("vd")
+	data := &T{}
+	err := v.Validate(data)
+	assertEqualError(t, err, "invalid parameter: A")
+	data.A = "b"
+	err = v.Validate(data)
+	assertEqualError(t, err, "invalid parameter: B")
+	data.B = 2
+	err = v.Validate(data)
+	assertNoError(t, err)
+
+	type T2 struct {
+		C string `vd:"in($)"`
+	}
+	data2 := &T2{}
+	err = v.Validate(data2)
+	assertEqualError(t, err, "invalid parameter: C")
+
+	type T3 struct {
+		C string `vd:"in($,1)"`
+	}
+	data3 := &T3{}
+	err = v.Validate(data3)
+	assertEqualError(t, err, "invalid parameter: C")
+}
+
+type (
+	Issue23A struct {
+		B *Issue23B
+		V int64 `vd:"$==0"`
+	}
+	Issue23B struct {
+		A *Issue23A
+		V int64 `vd:"$==0"`
+	}
+)
+
+func TestIssue23(t *testing.T) {
+	data := &Issue23B{A: &Issue23A{B: new(Issue23B)}}
+	err := vd.Validate(data, true)
+	assertNoError(t, err)
+}
+
+func TestIssue24(t *testing.T) {
+	type SubmitDoctorImportItem struct {
+		Name       string   `form:"name,required" json:"name,required" query:"name,required"`
+		Avatar     *string  `form:"avatar,omitempty" json:"avatar,omitempty" query:"avatar,omitempty"`
+		Idcard     string   `form:"idcard,required" json:"idcard,required" query:"idcard,required" vd:"len($)==18"`
+		IdcardPics []string `form:"idcard_pics,omitempty" json:"idcard_pics,omitempty" query:"idcard_pics,omitempty"`
+		Hosp       string   `form:"hosp,required" json:"hosp,required" query:"hosp,required"`
+		HospDept   string   `form:"hosp_dept,required" json:"hosp_dept,required" query:"hosp_dept,required"`
+		HospProv   *string  `form:"hosp_prov,omitempty" json:"hosp_prov,omitempty" query:"hosp_prov,omitempty"`
+		HospCity   *string  `form:"hosp_city,omitempty" json:"hosp_city,omitempty" query:"hosp_city,omitempty"`
+		HospCounty *string  `form:"hosp_county,omitempty" json:"hosp_county,omitempty" query:"hosp_county,omitempty"`
+		ProTit     string   `form:"pro_tit,required" json:"pro_tit,required" query:"pro_tit,required"`
+		ThTit      *string  `form:"th_tit,omitempty" json:"th_tit,omitempty" query:"th_tit,omitempty"`
+		ServDepts  *string  `form:"serv_depts,omitempty" json:"serv_depts,omitempty" query:"serv_depts,omitempty"`
+		TitCerts   []string `form:"tit_certs,omitempty" json:"tit_certs,omitempty" query:"tit_certs,omitempty"`
+		ThTitCerts []string `form:"th_tit_certs,omitempty" json:"th_tit_certs,omitempty" query:"th_tit_certs,omitempty"`
+		PracCerts  []string `form:"prac_certs,omitempty" json:"prac_certs,omitempty" query:"prac_certs,omitempty"`
+		QualCerts  []string `form:"qual_certs,omitempty" json:"qual_certs,omitempty" query:"qual_certs,omitempty"`
+		PracCertNo string   `form:"prac_cert_no,required" json:"prac_cert_no,required" query:"prac_cert_no,required" vd:"len($)==15"`
+		Goodat     *string  `form:"goodat,omitempty" json:"goodat,omitempty" query:"goodat,omitempty"`
+		Intro      *string  `form:"intro,omitempty" json:"intro,omitempty" query:"intro,omitempty"`
+		Linkman    string   `form:"linkman,required" json:"linkman,required" query:"linkman,required" vd:"email($)"`
+		Phone      string   `form:"phone,required" json:"phone,required" query:"phone,required" vd:"phone($,'CN')"`
+	}
+
+	type SubmitDoctorImportRequest struct {
+		SubmitDoctorImport []*SubmitDoctorImportItem `form:"submit_doctor_import,required" json:"submit_doctor_import,required"`
+	}
+	data := &SubmitDoctorImportRequest{SubmitDoctorImport: []*SubmitDoctorImportItem{{}}}
+	err := vd.Validate(data, true)
+	assertEqualError(t, err, "invalid parameter: SubmitDoctorImport[0].Idcard\tinvalid parameter: SubmitDoctorImport[0].PracCertNo\temail format is incorrect\tthe phone number supplied is not a number")
+}
+
+func TestStructSliceMap(t *testing.T) {
+	type F struct {
+		f struct {
+			g int `vd:"$%3==0"`
+		}
+	}
+	f := &F{}
+	f.f.g = 10
+	type S struct {
+		A map[string]*F
+		B []map[string]*F
+		C map[string][]map[string]F
+		// _ int
+	}
+	s := S{
+		A: map[string]*F{"x": f},
+		B: []map[string]*F{{"y": f}},
+		C: map[string][]map[string]F{"z": {{"zz": *f}}},
+	}
+	err := vd.Validate(s, true)
+	assertEqualError(t, err, "invalid parameter: A{v for k=x}.f.g\tinvalid parameter: B[0]{v for k=y}.f.g\tinvalid parameter: C{v for k=z}[0]{v for k=zz}.f.g")
+}
+
+func TestIssue30(t *testing.T) {
+	type TStruct struct {
+		TOk string `vd:"gt($,'0') && gt($, '1')" json:"t_ok"`
+		// TFail string `vd:"gt($,'0')" json:"t_fail"`
+	}
+	vd.RegFunc("gt", func(args ...interface{}) error {
+		return errors.New("force error")
+	})
+	assertEqualError(t, vd.Validate(&TStruct{TOk: "1"}), "invalid parameter: TOk")
+	// assertNoError(t, vd.Validate(&TStruct{TOk: "1", TFail: "1"}))
+}
+
+func TestIssue31(t *testing.T) {
+	type TStruct struct {
+		A []int32 `vd:"$ == nil || ($ != nil && range($, in(#v, 1, 2, 3))"`
+	}
+	assertEqualError(t, vd.Validate(&TStruct{A: []int32{1}}), "syntax error: \"($ != nil && range($, in(#v, 1, 2, 3))\"")
+	assertEqualError(t, vd.Validate(&TStruct{A: []int32{1}}), "syntax error: \"($ != nil && range($, in(#v, 1, 2, 3))\"")
+	assertEqualError(t, vd.Validate(&TStruct{A: []int32{1}}), "syntax error: \"($ != nil && range($, in(#v, 1, 2, 3))\"")
+}
+
+func TestRegexp(t *testing.T) {
+	type TStruct struct {
+		A string `vd:"regexp('(\\d+\\.){3}\\d+')"`
+	}
+	assertNoError(t, vd.Validate(&TStruct{A: "0.0.0.0"}))
+	assertEqualError(t, vd.Validate(&TStruct{A: "0...0"}), "invalid parameter: A")
+	assertEqualError(t, vd.Validate(&TStruct{A: "abc1"}), "invalid parameter: A")
+	assertEqualError(t, vd.Validate(&TStruct{A: "0?0?0?0"}), "invalid parameter: A")
+}
+
+func TestRangeIn(t *testing.T) {
+	type S struct {
+		F []string `vd:"range($, in(#v, '', 'ttp', 'euttp'))"`
+	}
+	err := vd.Validate(S{
+		F: []string{"ttp", "", "euttp"},
+	})
+	assertNoError(t, err)
+	err = vd.Validate(S{
+		F: []string{"ttp", "?", "euttp"},
+	})
+	assertEqualError(t, err, "invalid parameter: F")
+}