Add Spring Boot Todo API demo

.gitignore

@@ -0,0 +1,6 @@
+target/
+.idea/
+.classpath
+.project
+.settings/
+.DS_Store

.mvn/wrapper/maven-wrapper.properties

@@ -0,0 +1,3 @@
+wrapperVersion=3.3.4
+distributionType=only-script
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.12/apache-maven-3.9.12-bin.zip

Dockerfile

@@ -0,0 +1,12 @@
+FROM maven:3.9.9-eclipse-temurin-21 AS build
+WORKDIR /app
+COPY pom.xml .
+COPY src ./src
+RUN mvn -q -DskipTests package
+
+FROM eclipse-temurin:21-jre
+WORKDIR /app
+ENV PORT=7860
+COPY --from=build /app/target/java-demo-0.1.0.jar /app/app.jar
+EXPOSE 7860
+CMD ["java","-jar","/app/app.jar"]

README.md

@@ -1,10 +1,81 @@
 ---
-title: Java Demo
-emoji: 🏃
-colorFrom: pink
-colorTo: yellow
+title: Java 面试 Demo（Todo API）
+emoji: 🚀
+colorFrom: blue
+colorTo: purple
 sdk: docker
 pinned: false
 ---
 
-Check out the configuration reference at https://huggingface.co/docs/hub/spaces-config-reference
+# Java 面试 Demo（Todo API）
+
+这是一个用于面试展示的 Java 小项目：基于 Spring Boot 实现一个最小可用的 Todo REST API，并包含参数校验、统一错误返回和基础测试。适配 HuggingFace Spaces（Docker）运行。
+
+## 功能点
+
+- Todo CRUD：创建、查询列表、按 id 查询、更新、删除
+- 参数校验：title 必填、长度限制等
+- 统一错误返回：校验错误与 404 统一结构化返回
+- 基础测试：MockMvc 覆盖创建与校验失败场景
+- HuggingFace Spaces：Docker 方式部署，默认监听 7860 端口
+
+## 本地运行
+
+前置：
+
+- JDK 21（推荐）
+
+启动：
+
+```bash
+export JAVA_HOME=$(/usr/libexec/java_home -v 21)
+./mvnw test
+./mvnw spring-boot:run
+```
+
+访问：
+
+- 首页：http://localhost:7860/
+- 健康检查：http://localhost:7860/api/health
+
+## API 说明
+
+### 创建 Todo
+
+```bash
+curl -s -X POST http://localhost:7860/api/todos \
+  -H 'Content-Type: application/json' \
+  -d '{"title":"准备面试","description":"把这个项目讲清楚"}'
+```
+
+### 查询列表
+
+```bash
+curl -s http://localhost:7860/api/todos
+curl -s 'http://localhost:7860/api/todos?status=DONE'
+```
+
+### 更新 Todo
+
+```bash
+curl -s -X PUT http://localhost:7860/api/todos/1 \
+  -H 'Content-Type: application/json' \
+  -d '{"title":"准备面试","description":"更新一下状态","status":"DONE"}'
+```
+
+### 删除 Todo
+
+```bash
+curl -i -X DELETE http://localhost:7860/api/todos/1
+```
+
+## 设计要点（面试可讲）
+
+- 分层：Controller / Service 分离，Service 内存存储（ConcurrentHashMap）
+- 数据结构：使用 record 表达 DTO 与返回值
+- 异常处理：全局异常处理，输出稳定的 ErrorResponse 结构
+- 可部署性：读取 PORT 环境变量并监听 0.0.0.0，适配容器平台
+
+## 部署到 HuggingFace Spaces（Docker）
+
+本仓库已经包含 Dockerfile。将代码推送到 Space 仓库后，Space 会自动构建并启动。

mvnw

@@ -0,0 +1,295 @@
+#!/bin/sh
+# ----------------------------------------------------------------------------
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+# ----------------------------------------------------------------------------
+
+# ----------------------------------------------------------------------------
+# Apache Maven Wrapper startup batch script, version 3.3.4
+#
+# Optional ENV vars
+# -----------------
+#   JAVA_HOME - location of a JDK home dir, required when download maven via java source
+#   MVNW_REPOURL - repo url base for downloading maven distribution
+#   MVNW_USERNAME/MVNW_PASSWORD - user and password for downloading maven
+#   MVNW_VERBOSE - true: enable verbose log; debug: trace the mvnw script; others: silence the output
+# ----------------------------------------------------------------------------
+
+set -euf
+[ "${MVNW_VERBOSE-}" != debug ] || set -x
+
+# OS specific support.
+native_path() { printf %s\\n "$1"; }
+case "$(uname)" in
+CYGWIN* | MINGW*)
+  [ -z "${JAVA_HOME-}" ] || JAVA_HOME="$(cygpath --unix "$JAVA_HOME")"
+  native_path() { cygpath --path --windows "$1"; }
+  ;;
+esac
+
+# set JAVACMD and JAVACCMD
+set_java_home() {
+  # For Cygwin and MinGW, ensure paths are in Unix format before anything is touched
+  if [ -n "${JAVA_HOME-}" ]; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ]; then
+      # IBM's JDK on AIX uses strange locations for the executables
+      JAVACMD="$JAVA_HOME/jre/sh/java"
+      JAVACCMD="$JAVA_HOME/jre/sh/javac"
+    else
+      JAVACMD="$JAVA_HOME/bin/java"
+      JAVACCMD="$JAVA_HOME/bin/javac"
+
+      if [ ! -x "$JAVACMD" ] || [ ! -x "$JAVACCMD" ]; then
+        echo "The JAVA_HOME environment variable is not defined correctly, so mvnw cannot run." >&2
+        echo "JAVA_HOME is set to \"$JAVA_HOME\", but \"\$JAVA_HOME/bin/java\" or \"\$JAVA_HOME/bin/javac\" does not exist." >&2
+        return 1
+      fi
+    fi
+  else
+    JAVACMD="$(
+      'set' +e
+      'unset' -f command 2>/dev/null
+      'command' -v java
+    )" || :
+    JAVACCMD="$(
+      'set' +e
+      'unset' -f command 2>/dev/null
+      'command' -v javac
+    )" || :
+
+    if [ ! -x "${JAVACMD-}" ] || [ ! -x "${JAVACCMD-}" ]; then
+      echo "The java/javac command does not exist in PATH nor is JAVA_HOME set, so mvnw cannot run." >&2
+      return 1
+    fi
+  fi
+}
+
+# hash string like Java String::hashCode
+hash_string() {
+  str="${1:-}" h=0
+  while [ -n "$str" ]; do
+    char="${str%"${str#?}"}"
+    h=$(((h * 31 + $(LC_CTYPE=C printf %d "'$char")) % 4294967296))
+    str="${str#?}"
+  done
+  printf %x\\n $h
+}
+
+verbose() { :; }
+[ "${MVNW_VERBOSE-}" != true ] || verbose() { printf %s\\n "${1-}"; }
+
+die() {
+  printf %s\\n "$1" >&2
+  exit 1
+}
+
+trim() {
+  # MWRAPPER-139:
+  #   Trims trailing and leading whitespace, carriage returns, tabs, and linefeeds.
+  #   Needed for removing poorly interpreted newline sequences when running in more
+  #   exotic environments such as mingw bash on Windows.
+  printf "%s" "${1}" | tr -d '[:space:]'
+}
+
+scriptDir="$(dirname "$0")"
+scriptName="$(basename "$0")"
+
+# parse distributionUrl and optional distributionSha256Sum, requires .mvn/wrapper/maven-wrapper.properties
+while IFS="=" read -r key value; do
+  case "${key-}" in
+  distributionUrl) distributionUrl=$(trim "${value-}") ;;
+  distributionSha256Sum) distributionSha256Sum=$(trim "${value-}") ;;
+  esac
+done <"$scriptDir/.mvn/wrapper/maven-wrapper.properties"
+[ -n "${distributionUrl-}" ] || die "cannot read distributionUrl property in $scriptDir/.mvn/wrapper/maven-wrapper.properties"
+
+case "${distributionUrl##*/}" in
+maven-mvnd-*bin.*)
+  MVN_CMD=mvnd.sh _MVNW_REPO_PATTERN=/maven/mvnd/
+  case "${PROCESSOR_ARCHITECTURE-}${PROCESSOR_ARCHITEW6432-}:$(uname -a)" in
+  *AMD64:CYGWIN* | *AMD64:MINGW*) distributionPlatform=windows-amd64 ;;
+  :Darwin*x86_64) distributionPlatform=darwin-amd64 ;;
+  :Darwin*arm64) distributionPlatform=darwin-aarch64 ;;
+  :Linux*x86_64*) distributionPlatform=linux-amd64 ;;
+  *)
+    echo "Cannot detect native platform for mvnd on $(uname)-$(uname -m), use pure java version" >&2
+    distributionPlatform=linux-amd64
+    ;;
+  esac
+  distributionUrl="${distributionUrl%-bin.*}-$distributionPlatform.zip"
+  ;;
+maven-mvnd-*) MVN_CMD=mvnd.sh _MVNW_REPO_PATTERN=/maven/mvnd/ ;;
+*) MVN_CMD="mvn${scriptName#mvnw}" _MVNW_REPO_PATTERN=/org/apache/maven/ ;;
+esac
+
+# apply MVNW_REPOURL and calculate MAVEN_HOME
+# maven home pattern: ~/.m2/wrapper/dists/{apache-maven-<version>,maven-mvnd-<version>-<platform>}/<hash>
+[ -z "${MVNW_REPOURL-}" ] || distributionUrl="$MVNW_REPOURL$_MVNW_REPO_PATTERN${distributionUrl#*"$_MVNW_REPO_PATTERN"}"
+distributionUrlName="${distributionUrl##*/}"
+distributionUrlNameMain="${distributionUrlName%.*}"
+distributionUrlNameMain="${distributionUrlNameMain%-bin}"
+MAVEN_USER_HOME="${MAVEN_USER_HOME:-${HOME}/.m2}"
+MAVEN_HOME="${MAVEN_USER_HOME}/wrapper/dists/${distributionUrlNameMain-}/$(hash_string "$distributionUrl")"
+
+exec_maven() {
+  unset MVNW_VERBOSE MVNW_USERNAME MVNW_PASSWORD MVNW_REPOURL || :
+  exec "$MAVEN_HOME/bin/$MVN_CMD" "$@" || die "cannot exec $MAVEN_HOME/bin/$MVN_CMD"
+}
+
+if [ -d "$MAVEN_HOME" ]; then
+  verbose "found existing MAVEN_HOME at $MAVEN_HOME"
+  exec_maven "$@"
+fi
+
+case "${distributionUrl-}" in
+*?-bin.zip | *?maven-mvnd-?*-?*.zip) ;;
+*) die "distributionUrl is not valid, must match *-bin.zip or maven-mvnd-*.zip, but found '${distributionUrl-}'" ;;
+esac
+
+# prepare tmp dir
+if TMP_DOWNLOAD_DIR="$(mktemp -d)" && [ -d "$TMP_DOWNLOAD_DIR" ]; then
+  clean() { rm -rf -- "$TMP_DOWNLOAD_DIR"; }
+  trap clean HUP INT TERM EXIT
+else
+  die "cannot create temp dir"
+fi
+
+mkdir -p -- "${MAVEN_HOME%/*}"
+
+# Download and Install Apache Maven
+verbose "Couldn't find MAVEN_HOME, downloading and installing it ..."
+verbose "Downloading from: $distributionUrl"
+verbose "Downloading to: $TMP_DOWNLOAD_DIR/$distributionUrlName"
+
+# select .zip or .tar.gz
+if ! command -v unzip >/dev/null; then
+  distributionUrl="${distributionUrl%.zip}.tar.gz"
+  distributionUrlName="${distributionUrl##*/}"
+fi
+
+# verbose opt
+__MVNW_QUIET_WGET=--quiet __MVNW_QUIET_CURL=--silent __MVNW_QUIET_UNZIP=-q __MVNW_QUIET_TAR=''
+[ "${MVNW_VERBOSE-}" != true ] || __MVNW_QUIET_WGET='' __MVNW_QUIET_CURL='' __MVNW_QUIET_UNZIP='' __MVNW_QUIET_TAR=v
+
+# normalize http auth
+case "${MVNW_PASSWORD:+has-password}" in
+'') MVNW_USERNAME='' MVNW_PASSWORD='' ;;
+has-password) [ -n "${MVNW_USERNAME-}" ] || MVNW_USERNAME='' MVNW_PASSWORD='' ;;
+esac
+
+if [ -z "${MVNW_USERNAME-}" ] && command -v wget >/dev/null; then
+  verbose "Found wget ... using wget"
+  wget ${__MVNW_QUIET_WGET:+"$__MVNW_QUIET_WGET"} "$distributionUrl" -O "$TMP_DOWNLOAD_DIR/$distributionUrlName" || die "wget: Failed to fetch $distributionUrl"
+elif [ -z "${MVNW_USERNAME-}" ] && command -v curl >/dev/null; then
+  verbose "Found curl ... using curl"
+  curl ${__MVNW_QUIET_CURL:+"$__MVNW_QUIET_CURL"} -f -L -o "$TMP_DOWNLOAD_DIR/$distributionUrlName" "$distributionUrl" || die "curl: Failed to fetch $distributionUrl"
+elif set_java_home; then
+  verbose "Falling back to use Java to download"
+  javaSource="$TMP_DOWNLOAD_DIR/Downloader.java"
+  targetZip="$TMP_DOWNLOAD_DIR/$distributionUrlName"
+  cat >"$javaSource" <<-END
+	public class Downloader extends java.net.Authenticator
+	{
+	  protected java.net.PasswordAuthentication getPasswordAuthentication()
+	  {
+	    return new java.net.PasswordAuthentication( System.getenv( "MVNW_USERNAME" ), System.getenv( "MVNW_PASSWORD" ).toCharArray() );
+	  }
+	  public static void main( String[] args ) throws Exception
+	  {
+	    setDefault( new Downloader() );
+	    java.nio.file.Files.copy( java.net.URI.create( args[0] ).toURL().openStream(), java.nio.file.Paths.get( args[1] ).toAbsolutePath().normalize() );
+	  }
+	}
+	END
+  # For Cygwin/MinGW, switch paths to Windows format before running javac and java
+  verbose " - Compiling Downloader.java ..."
+  "$(native_path "$JAVACCMD")" "$(native_path "$javaSource")" || die "Failed to compile Downloader.java"
+  verbose " - Running Downloader.java ..."
+  "$(native_path "$JAVACMD")" -cp "$(native_path "$TMP_DOWNLOAD_DIR")" Downloader "$distributionUrl" "$(native_path "$targetZip")"
+fi
+
+# If specified, validate the SHA-256 sum of the Maven distribution zip file
+if [ -n "${distributionSha256Sum-}" ]; then
+  distributionSha256Result=false
+  if [ "$MVN_CMD" = mvnd.sh ]; then
+    echo "Checksum validation is not supported for maven-mvnd." >&2
+    echo "Please disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties." >&2
+    exit 1
+  elif command -v sha256sum >/dev/null; then
+    if echo "$distributionSha256Sum  $TMP_DOWNLOAD_DIR/$distributionUrlName" | sha256sum -c - >/dev/null 2>&1; then
+      distributionSha256Result=true
+    fi
+  elif command -v shasum >/dev/null; then
+    if echo "$distributionSha256Sum  $TMP_DOWNLOAD_DIR/$distributionUrlName" | shasum -a 256 -c >/dev/null 2>&1; then
+      distributionSha256Result=true
+    fi
+  else
+    echo "Checksum validation was requested but neither 'sha256sum' or 'shasum' are available." >&2
+    echo "Please install either command, or disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties." >&2
+    exit 1
+  fi
+  if [ $distributionSha256Result = false ]; then
+    echo "Error: Failed to validate Maven distribution SHA-256, your Maven distribution might be compromised." >&2
+    echo "If you updated your Maven version, you need to update the specified distributionSha256Sum property." >&2
+    exit 1
+  fi
+fi
+
+# unzip and move
+if command -v unzip >/dev/null; then
+  unzip ${__MVNW_QUIET_UNZIP:+"$__MVNW_QUIET_UNZIP"} "$TMP_DOWNLOAD_DIR/$distributionUrlName" -d "$TMP_DOWNLOAD_DIR" || die "failed to unzip"
+else
+  tar xzf${__MVNW_QUIET_TAR:+"$__MVNW_QUIET_TAR"} "$TMP_DOWNLOAD_DIR/$distributionUrlName" -C "$TMP_DOWNLOAD_DIR" || die "failed to untar"
+fi
+
+# Find the actual extracted directory name (handles snapshots where filename != directory name)
+actualDistributionDir=""
+
+# First try the expected directory name (for regular distributions)
+if [ -d "$TMP_DOWNLOAD_DIR/$distributionUrlNameMain" ]; then
+  if [ -f "$TMP_DOWNLOAD_DIR/$distributionUrlNameMain/bin/$MVN_CMD" ]; then
+    actualDistributionDir="$distributionUrlNameMain"
+  fi
+fi
+
+# If not found, search for any directory with the Maven executable (for snapshots)
+if [ -z "$actualDistributionDir" ]; then
+  # enable globbing to iterate over items
+  set +f
+  for dir in "$TMP_DOWNLOAD_DIR"/*; do
+    if [ -d "$dir" ]; then
+      if [ -f "$dir/bin/$MVN_CMD" ]; then
+        actualDistributionDir="$(basename "$dir")"
+        break
+      fi
+    fi
+  done
+  set -f
+fi
+
+if [ -z "$actualDistributionDir" ]; then
+  verbose "Contents of $TMP_DOWNLOAD_DIR:"
+  verbose "$(ls -la "$TMP_DOWNLOAD_DIR")"
+  die "Could not find Maven distribution directory in extracted archive"
+fi
+
+verbose "Found extracted Maven distribution directory: $actualDistributionDir"
+printf %s\\n "$distributionUrl" >"$TMP_DOWNLOAD_DIR/$actualDistributionDir/mvnw.url"
+mv -- "$TMP_DOWNLOAD_DIR/$actualDistributionDir" "$MAVEN_HOME" || [ -d "$MAVEN_HOME" ] || die "fail to move MAVEN_HOME"
+
+clean || :
+exec_maven "$@"

mvnw.cmd

@@ -0,0 +1,189 @@
+<# : batch portion
+@REM ----------------------------------------------------------------------------
+@REM Licensed to the Apache Software Foundation (ASF) under one
+@REM or more contributor license agreements.  See the NOTICE file
+@REM distributed with this work for additional information
+@REM regarding copyright ownership.  The ASF licenses this file
+@REM to you under the Apache License, Version 2.0 (the
+@REM "License"); you may not use this file except in compliance
+@REM with the License.  You may obtain a copy of the License at
+@REM
+@REM    http://www.apache.org/licenses/LICENSE-2.0
+@REM
+@REM Unless required by applicable law or agreed to in writing,
+@REM software distributed under the License is distributed on an
+@REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+@REM KIND, either express or implied.  See the License for the
+@REM specific language governing permissions and limitations
+@REM under the License.
+@REM ----------------------------------------------------------------------------
+
+@REM ----------------------------------------------------------------------------
+@REM Apache Maven Wrapper startup batch script, version 3.3.4
+@REM
+@REM Optional ENV vars
+@REM   MVNW_REPOURL - repo url base for downloading maven distribution
+@REM   MVNW_USERNAME/MVNW_PASSWORD - user and password for downloading maven
+@REM   MVNW_VERBOSE - true: enable verbose log; others: silence the output
+@REM ----------------------------------------------------------------------------
+
+@IF "%__MVNW_ARG0_NAME__%"=="" (SET __MVNW_ARG0_NAME__=%~nx0)
+@SET __MVNW_CMD__=
+@SET __MVNW_ERROR__=
+@SET __MVNW_PSMODULEP_SAVE=%PSModulePath%
+@SET PSModulePath=
+@FOR /F "usebackq tokens=1* delims==" %%A IN (`powershell -noprofile "& {$scriptDir='%~dp0'; $script='%__MVNW_ARG0_NAME__%'; icm -ScriptBlock ([Scriptblock]::Create((Get-Content -Raw '%~f0'))) -NoNewScope}"`) DO @(
+  IF "%%A"=="MVN_CMD" (set __MVNW_CMD__=%%B) ELSE IF "%%B"=="" (echo %%A) ELSE (echo %%A=%%B)
+)
+@SET PSModulePath=%__MVNW_PSMODULEP_SAVE%
+@SET __MVNW_PSMODULEP_SAVE=
+@SET __MVNW_ARG0_NAME__=
+@SET MVNW_USERNAME=
+@SET MVNW_PASSWORD=
+@IF NOT "%__MVNW_CMD__%"=="" ("%__MVNW_CMD__%" %*)
+@echo Cannot start maven from wrapper >&2 && exit /b 1
+@GOTO :EOF
+: end batch / begin powershell #>
+
+$ErrorActionPreference = "Stop"
+if ($env:MVNW_VERBOSE -eq "true") {
+  $VerbosePreference = "Continue"
+}
+
+# calculate distributionUrl, requires .mvn/wrapper/maven-wrapper.properties
+$distributionUrl = (Get-Content -Raw "$scriptDir/.mvn/wrapper/maven-wrapper.properties" | ConvertFrom-StringData).distributionUrl
+if (!$distributionUrl) {
+  Write-Error "cannot read distributionUrl property in $scriptDir/.mvn/wrapper/maven-wrapper.properties"
+}
+
+switch -wildcard -casesensitive ( $($distributionUrl -replace '^.*/','') ) {
+  "maven-mvnd-*" {
+    $USE_MVND = $true
+    $distributionUrl = $distributionUrl -replace '-bin\.[^.]*$',"-windows-amd64.zip"
+    $MVN_CMD = "mvnd.cmd"
+    break
+  }
+  default {
+    $USE_MVND = $false
+    $MVN_CMD = $script -replace '^mvnw','mvn'
+    break
+  }
+}
+
+# apply MVNW_REPOURL and calculate MAVEN_HOME
+# maven home pattern: ~/.m2/wrapper/dists/{apache-maven-<version>,maven-mvnd-<version>-<platform>}/<hash>
+if ($env:MVNW_REPOURL) {
+  $MVNW_REPO_PATTERN = if ($USE_MVND -eq $False) { "/org/apache/maven/" } else { "/maven/mvnd/" }
+  $distributionUrl = "$env:MVNW_REPOURL$MVNW_REPO_PATTERN$($distributionUrl -replace "^.*$MVNW_REPO_PATTERN",'')"
+}
+$distributionUrlName = $distributionUrl -replace '^.*/',''
+$distributionUrlNameMain = $distributionUrlName -replace '\.[^.]*$','' -replace '-bin$',''
+
+$MAVEN_M2_PATH = "$HOME/.m2"
+if ($env:MAVEN_USER_HOME) {
+  $MAVEN_M2_PATH = "$env:MAVEN_USER_HOME"
+}
+
+if (-not (Test-Path -Path $MAVEN_M2_PATH)) {
+    New-Item -Path $MAVEN_M2_PATH -ItemType Directory | Out-Null
+}
+
+$MAVEN_WRAPPER_DISTS = $null
+if ((Get-Item $MAVEN_M2_PATH).Target[0] -eq $null) {
+  $MAVEN_WRAPPER_DISTS = "$MAVEN_M2_PATH/wrapper/dists"
+} else {
+  $MAVEN_WRAPPER_DISTS = (Get-Item $MAVEN_M2_PATH).Target[0] + "/wrapper/dists"
+}
+
+$MAVEN_HOME_PARENT = "$MAVEN_WRAPPER_DISTS/$distributionUrlNameMain"
+$MAVEN_HOME_NAME = ([System.Security.Cryptography.SHA256]::Create().ComputeHash([byte[]][char[]]$distributionUrl) | ForEach-Object {$_.ToString("x2")}) -join ''
+$MAVEN_HOME = "$MAVEN_HOME_PARENT/$MAVEN_HOME_NAME"
+
+if (Test-Path -Path "$MAVEN_HOME" -PathType Container) {
+  Write-Verbose "found existing MAVEN_HOME at $MAVEN_HOME"
+  Write-Output "MVN_CMD=$MAVEN_HOME/bin/$MVN_CMD"
+  exit $?
+}
+
+if (! $distributionUrlNameMain -or ($distributionUrlName -eq $distributionUrlNameMain)) {
+  Write-Error "distributionUrl is not valid, must end with *-bin.zip, but found $distributionUrl"
+}
+
+# prepare tmp dir
+$TMP_DOWNLOAD_DIR_HOLDER = New-TemporaryFile
+$TMP_DOWNLOAD_DIR = New-Item -Itemtype Directory -Path "$TMP_DOWNLOAD_DIR_HOLDER.dir"
+$TMP_DOWNLOAD_DIR_HOLDER.Delete() | Out-Null
+trap {
+  if ($TMP_DOWNLOAD_DIR.Exists) {
+    try { Remove-Item $TMP_DOWNLOAD_DIR -Recurse -Force | Out-Null }
+    catch { Write-Warning "Cannot remove $TMP_DOWNLOAD_DIR" }
+  }
+}
+
+New-Item -Itemtype Directory -Path "$MAVEN_HOME_PARENT" -Force | Out-Null
+
+# Download and Install Apache Maven
+Write-Verbose "Couldn't find MAVEN_HOME, downloading and installing it ..."
+Write-Verbose "Downloading from: $distributionUrl"
+Write-Verbose "Downloading to: $TMP_DOWNLOAD_DIR/$distributionUrlName"
+
+$webclient = New-Object System.Net.WebClient
+if ($env:MVNW_USERNAME -and $env:MVNW_PASSWORD) {
+  $webclient.Credentials = New-Object System.Net.NetworkCredential($env:MVNW_USERNAME, $env:MVNW_PASSWORD)
+}
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+$webclient.DownloadFile($distributionUrl, "$TMP_DOWNLOAD_DIR/$distributionUrlName") | Out-Null
+
+# If specified, validate the SHA-256 sum of the Maven distribution zip file
+$distributionSha256Sum = (Get-Content -Raw "$scriptDir/.mvn/wrapper/maven-wrapper.properties" | ConvertFrom-StringData).distributionSha256Sum
+if ($distributionSha256Sum) {
+  if ($USE_MVND) {
+    Write-Error "Checksum validation is not supported for maven-mvnd. `nPlease disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties."
+  }
+  Import-Module $PSHOME\Modules\Microsoft.PowerShell.Utility -Function Get-FileHash
+  if ((Get-FileHash "$TMP_DOWNLOAD_DIR/$distributionUrlName" -Algorithm SHA256).Hash.ToLower() -ne $distributionSha256Sum) {
+    Write-Error "Error: Failed to validate Maven distribution SHA-256, your Maven distribution might be compromised. If you updated your Maven version, you need to update the specified distributionSha256Sum property."
+  }
+}
+
+# unzip and move
+Expand-Archive "$TMP_DOWNLOAD_DIR/$distributionUrlName" -DestinationPath "$TMP_DOWNLOAD_DIR" | Out-Null
+
+# Find the actual extracted directory name (handles snapshots where filename != directory name)
+$actualDistributionDir = ""
+
+# First try the expected directory name (for regular distributions)
+$expectedPath = Join-Path "$TMP_DOWNLOAD_DIR" "$distributionUrlNameMain"
+$expectedMvnPath = Join-Path "$expectedPath" "bin/$MVN_CMD"
+if ((Test-Path -Path $expectedPath -PathType Container) -and (Test-Path -Path $expectedMvnPath -PathType Leaf)) {
+  $actualDistributionDir = $distributionUrlNameMain
+}
+
+# If not found, search for any directory with the Maven executable (for snapshots)
+if (!$actualDistributionDir) {
+  Get-ChildItem -Path "$TMP_DOWNLOAD_DIR" -Directory | ForEach-Object {
+    $testPath = Join-Path $_.FullName "bin/$MVN_CMD"
+    if (Test-Path -Path $testPath -PathType Leaf) {
+      $actualDistributionDir = $_.Name
+    }
+  }
+}
+
+if (!$actualDistributionDir) {
+  Write-Error "Could not find Maven distribution directory in extracted archive"
+}
+
+Write-Verbose "Found extracted Maven distribution directory: $actualDistributionDir"
+Rename-Item -Path "$TMP_DOWNLOAD_DIR/$actualDistributionDir" -NewName $MAVEN_HOME_NAME | Out-Null
+try {
+  Move-Item -Path "$TMP_DOWNLOAD_DIR/$MAVEN_HOME_NAME" -Destination $MAVEN_HOME_PARENT | Out-Null
+} catch {
+  if (! (Test-Path -Path "$MAVEN_HOME" -PathType Container)) {
+    Write-Error "fail to move MAVEN_HOME"
+  }
+} finally {
+  try { Remove-Item $TMP_DOWNLOAD_DIR -Recurse -Force | Out-Null }
+  catch { Write-Warning "Cannot remove $TMP_DOWNLOAD_DIR" }
+}
+
+Write-Output "MVN_CMD=$MAVEN_HOME/bin/$MVN_CMD"

pom.xml

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>3.4.1</version>
+        <relativePath/>
+    </parent>
+
+    <groupId>com.duqing2026</groupId>
+    <artifactId>java-demo</artifactId>
+    <version>0.1.0</version>
+    <name>java-demo</name>
+    <description>Interview-ready Java demo project</description>
+
+    <properties>
+        <java.version>21</java.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-validation</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <argLine>-XX:+EnableDynamicAgentLoading</argLine>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

src/main/java/com/duqing2026/javademo/JavaDemoApplication.java

@@ -0,0 +1,11 @@
+package com.duqing2026.javademo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class JavaDemoApplication {
+    public static void main(String[] args) {
+        SpringApplication.run(JavaDemoApplication.class, args);
+    }
+}

src/main/java/com/duqing2026/javademo/api/ErrorResponse.java

@@ -0,0 +1,14 @@
+package com.duqing2026.javademo.api;
+
+import java.time.Instant;
+import java.util.Map;
+
+public record ErrorResponse(
+        Instant timestamp,
+        int status,
+        String error,
+        String message,
+        String path,
+        Map<String, Object> details
+) {
+}

src/main/java/com/duqing2026/javademo/api/GlobalExceptionHandler.java

@@ -0,0 +1,63 @@
+package com.duqing2026.javademo.api;
+
+import jakarta.servlet.http.HttpServletRequest;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.validation.FieldError;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+
+import java.time.Instant;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+@RestControllerAdvice
+public class GlobalExceptionHandler {
+
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ResponseEntity<ErrorResponse> handleValidation(MethodArgumentNotValidException ex, HttpServletRequest request) {
+        Map<String, Object> details = new LinkedHashMap<>();
+        for (FieldError fieldError : ex.getBindingResult().getFieldErrors()) {
+            details.put(fieldError.getField(), fieldError.getDefaultMessage());
+        }
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(
+                new ErrorResponse(
+                        Instant.now(),
+                        HttpStatus.BAD_REQUEST.value(),
+                        HttpStatus.BAD_REQUEST.getReasonPhrase(),
+                        "参数校验失败",
+                        request.getRequestURI(),
+                        details
+                )
+        );
+    }
+
+    @ExceptionHandler(TodoNotFoundException.class)
+    public ResponseEntity<ErrorResponse> handleNotFound(TodoNotFoundException ex, HttpServletRequest request) {
+        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(
+                new ErrorResponse(
+                        Instant.now(),
+                        HttpStatus.NOT_FOUND.value(),
+                        HttpStatus.NOT_FOUND.getReasonPhrase(),
+                        ex.getMessage(),
+                        request.getRequestURI(),
+                        Map.of()
+                )
+        );
+    }
+
+    @ExceptionHandler(Exception.class)
+    public ResponseEntity<ErrorResponse> handleOther(Exception ex, HttpServletRequest request) {
+        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(
+                new ErrorResponse(
+                        Instant.now(),
+                        HttpStatus.INTERNAL_SERVER_ERROR.value(),
+                        HttpStatus.INTERNAL_SERVER_ERROR.getReasonPhrase(),
+                        "服务端异常",
+                        request.getRequestURI(),
+                        Map.of("exception", ex.getClass().getName())
+                )
+        );
+    }
+}

src/main/java/com/duqing2026/javademo/api/TodoNotFoundException.java

@@ -0,0 +1,7 @@
+package com.duqing2026.javademo.api;
+
+public class TodoNotFoundException extends RuntimeException {
+    public TodoNotFoundException(long id) {
+        super("Todo 不存在: id=" + id);
+    }
+}

src/main/java/com/duqing2026/javademo/system/HealthController.java

@@ -0,0 +1,18 @@
+package com.duqing2026.javademo.system;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.time.Instant;
+import java.util.Map;
+
+@RestController
+public class HealthController {
+    @GetMapping("/api/health")
+    public Map<String, Object> health() {
+        return Map.of(
+                "status", "UP",
+                "time", Instant.now().toString()
+        );
+    }
+}

src/main/java/com/duqing2026/javademo/todo/TodoController.java

@@ -0,0 +1,45 @@
+package com.duqing2026.javademo.todo;
+
+import jakarta.validation.Valid;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+import java.util.Optional;
+
+@RestController
+@RequestMapping("/api/todos")
+public class TodoController {
+    private final TodoService todoService;
+
+    public TodoController(TodoService todoService) {
+        this.todoService = todoService;
+    }
+
+    @PostMapping
+    @ResponseStatus(HttpStatus.CREATED)
+    public TodoItem create(@Valid @RequestBody TodoCreateRequest request) {
+        return todoService.create(request);
+    }
+
+    @GetMapping
+    public List<TodoItem> list(@RequestParam(required = false) TodoStatus status) {
+        return todoService.list(Optional.ofNullable(status));
+    }
+
+    @GetMapping("/{id}")
+    public TodoItem get(@PathVariable long id) {
+        return todoService.get(id);
+    }
+
+    @PutMapping("/{id}")
+    public TodoItem update(@PathVariable long id, @Valid @RequestBody TodoUpdateRequest request) {
+        return todoService.update(id, request);
+    }
+
+    @DeleteMapping("/{id}")
+    @ResponseStatus(HttpStatus.NO_CONTENT)
+    public void delete(@PathVariable long id) {
+        todoService.delete(id);
+    }
+}

src/main/java/com/duqing2026/javademo/todo/TodoCreateRequest.java

@@ -0,0 +1,14 @@
+package com.duqing2026.javademo.todo;
+
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Size;
+
+public record TodoCreateRequest(
+        @NotBlank(message = "title 不能为空")
+        @Size(max = 80, message = "title 最多 80 个字符")
+        String title,
+
+        @Size(max = 400, message = "description 最多 400 个字符")
+        String description
+) {
+}

src/main/java/com/duqing2026/javademo/todo/TodoItem.java

@@ -0,0 +1,13 @@
+package com.duqing2026.javademo.todo;
+
+import java.time.Instant;
+
+public record TodoItem(
+        long id,
+        String title,
+        String description,
+        TodoStatus status,
+        Instant createdAt,
+        Instant updatedAt
+) {
+}

src/main/java/com/duqing2026/javademo/todo/TodoService.java

@@ -0,0 +1,81 @@
+package com.duqing2026.javademo.todo;
+
+import com.duqing2026.javademo.api.TodoNotFoundException;
+import org.springframework.stereotype.Service;
+
+import java.time.Instant;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicLong;
+
+@Service
+public class TodoService {
+    private final AtomicLong idGenerator = new AtomicLong(0);
+    private final ConcurrentMap<Long, TodoItem> store = new ConcurrentHashMap<>();
+
+    public TodoItem create(TodoCreateRequest request) {
+        long id = idGenerator.incrementAndGet();
+        Instant now = Instant.now();
+        TodoItem item = new TodoItem(
+                id,
+                request.title().trim(),
+                normalizeDescription(request.description()),
+                TodoStatus.OPEN,
+                now,
+                now
+        );
+        store.put(id, item);
+        return item;
+    }
+
+    public List<TodoItem> list(Optional<TodoStatus> status) {
+        return store.values().stream()
+                .filter(item -> status.map(s -> item.status() == s).orElse(true))
+                .sorted(Comparator.comparingLong(TodoItem::id))
+                .toList();
+    }
+
+    public TodoItem get(long id) {
+        TodoItem item = store.get(id);
+        if (item == null) {
+            throw new TodoNotFoundException(id);
+        }
+        return item;
+    }
+
+    public TodoItem update(long id, TodoUpdateRequest request) {
+        return store.compute(id, (key, existing) -> {
+            if (existing == null) {
+                throw new TodoNotFoundException(id);
+            }
+            Instant now = Instant.now();
+            TodoStatus nextStatus = request.status() == null ? existing.status() : request.status();
+            return new TodoItem(
+                    existing.id(),
+                    request.title().trim(),
+                    normalizeDescription(request.description()),
+                    nextStatus,
+                    existing.createdAt(),
+                    now
+            );
+        });
+    }
+
+    public void delete(long id) {
+        TodoItem removed = store.remove(id);
+        if (removed == null) {
+            throw new TodoNotFoundException(id);
+        }
+    }
+
+    private String normalizeDescription(String description) {
+        if (description == null) {
+            return null;
+        }
+        String trimmed = description.trim();
+        return trimmed.isEmpty() ? null : trimmed;
+    }
+}

src/main/java/com/duqing2026/javademo/todo/TodoStatus.java

@@ -0,0 +1,6 @@
+package com.duqing2026.javademo.todo;
+
+public enum TodoStatus {
+    OPEN,
+    DONE
+}

src/main/java/com/duqing2026/javademo/todo/TodoUpdateRequest.java

@@ -0,0 +1,16 @@
+package com.duqing2026.javademo.todo;
+
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Size;
+
+public record TodoUpdateRequest(
+        @NotBlank(message = "title 不能为空")
+        @Size(max = 80, message = "title 最多 80 个字符")
+        String title,
+
+        @Size(max = 400, message = "description 最多 400 个字符")
+        String description,
+
+        TodoStatus status
+) {
+}

src/main/resources/application.properties

@@ -0,0 +1,3 @@
+server.address=0.0.0.0
+server.port=${PORT:7860}
+spring.jackson.time-zone=UTC

src/main/resources/static/index.html

@@ -0,0 +1,42 @@
+<!doctype html>
+<html lang="zh-CN">
+<head>
+  <meta charset="utf-8"/>
+  <meta name="viewport" content="width=device-width, initial-scale=1"/>
+  <title>Java Demo - Todo API</title>
+  <style>
+    body { font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial; margin: 32px; line-height: 1.6; }
+    code, pre { background: #f6f8fa; padding: 2px 6px; border-radius: 6px; }
+    pre { padding: 12px; overflow: auto; }
+    .box { border: 1px solid #e5e7eb; border-radius: 10px; padding: 16px; margin: 16px 0; }
+  </style>
+</head>
+<body>
+  <h1>Java Demo：Todo API</h1>
+  <p>这是一个用于面试展示的 Java/Spring Boot 小项目：提供一个最小可用的 Todo 管理 REST API，并包含参数校验、统一错误返回与单元测试。</p>
+
+  <div class="box">
+    <h2>快速检查</h2>
+    <p><a href="/api/health">/api/health</a></p>
+  </div>
+
+  <div class="box">
+    <h2>API 示例（curl）</h2>
+    <pre><code>curl -s http://localhost:7860/api/health
+
+curl -s -X POST http://localhost:7860/api/todos \
+  -H 'Content-Type: application/json' \
+  -d '{"title":"准备面试","description":"把这个项目讲清楚"}'
+
+curl -s http://localhost:7860/api/todos
+
+curl -s -X PUT http://localhost:7860/api/todos/1 \
+  -H 'Content-Type: application/json' \
+  -d '{"title":"准备面试","description":"更新一下状态","status":"DONE"}'
+
+curl -i -X DELETE http://localhost:7860/api/todos/1</code></pre>
+  </div>
+
+  <p>更多说明见仓库 README.md。</p>
+</body>
+</html>

src/test/java/com/duqing2026/javademo/todo/TodoControllerTest.java

@@ -0,0 +1,57 @@
+package com.duqing2026.javademo.todo;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.hamcrest.Matchers.*;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
+
+@SpringBootTest
+@AutoConfigureMockMvc
+class TodoControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Autowired
+    private ObjectMapper objectMapper;
+
+    @Test
+    void createAndGetTodo() throws Exception {
+        TodoCreateRequest createRequest = new TodoCreateRequest("准备面试", "写一个可运行的 demo");
+
+        String createdJson = mockMvc.perform(post("/api/todos")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content(objectMapper.writeValueAsString(createRequest)))
+                .andExpect(status().isCreated())
+                .andExpect(jsonPath("$.id", greaterThan(0)))
+                .andExpect(jsonPath("$.title", is("准备面试")))
+                .andExpect(jsonPath("$.status", is("OPEN")))
+                .andReturn()
+                .getResponse()
+                .getContentAsString();
+
+        TodoItem created = objectMapper.readValue(createdJson, TodoItem.class);
+
+        mockMvc.perform(get("/api/todos/{id}", created.id()))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.id", is((int) created.id())))
+                .andExpect(jsonPath("$.title", is("准备面试")));
+    }
+
+    @Test
+    void validationErrorReturnsDetails() throws Exception {
+        mockMvc.perform(post("/api/todos")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("{\"title\":\"\",\"description\":\"x\"}"))
+                .andExpect(status().isBadRequest())
+                .andExpect(jsonPath("$.message", is("参数校验失败")))
+                .andExpect(jsonPath("$.details.title", notNullValue()));
+    }
+}