Scaffolding Reference | MuleSoft Documentation
# Scaffolding Reference
Generate the backbone of a REST API implementation based on RESTful API Modeling Language (RAML) or OpenAPI Specifications (OAS) with APIkit for REST scaffolder.
## API Scaffolding
Studio offers several ways to scaffold an API:
  * From **New Mule Project wizard** , select **Scaffold Flows From These API Specifications** when importing a published API from Exchange or Maven, importing from a local file, or downloading from Design Center.
  * From **Package Explorer** , right-click the API file and select **Mule** > **Generate flows from Local REST API**.
  * From **Package Explorer** , right-click the API dependency and select **Generate flows** from its context menu.


Scaffolding from a local file is not supported for OAS. Scaffolding OAS APIs is available only for published assets in Exchange.   
---  
## Implementation Reference
When scaffolding a REST API specification, APIkit generates the following components:
  * A main flow that acts as the entry point and includes:
    * HTTP Listener as a source
    * APIkit Router as the main operation
APIkit Router is a message processor that directs messages from incoming API requests to the corresponding Mule flows and generates a serialized response using default values. For example, in an invalid request, APIkit generates a `bad request` response, and a missing associated flow for the requested API resource results in a `not implemented` response.
While APIkit Router validates aspects such as request payload, headers, query parameters, and URI parameters, it does not validate all elements specified in an API specification. Specifically, the router does not perform security-related validation, such as authentication enforcement. Instead, the API gateway policies are responsible for this validation, which occurs before the request reaches the router.
    * Error Handler
  * A secondary flow that exposes the API console and includes:
    * HTTP Listener as a source
    * APIkit Console as the main operation
    * Error Handler
  * In addition to N flows, one per API action-resource-content-type combination, each flow includes:
    * No source (this option is available for APIkit for REST and SOAP applications only)
    * A mock implementation you substitute later with your actual business logic


## Example
```
<mule>
  <apikit:config name="api-config" api="api.raml" outboundHeadersMapName="outboundHeaders" httpStatusVarName="httpStatus" />
  <flow name="api-main">
    <http:listener config-ref="HTTP_Listener_config" path="/api/*">
      <http:response statusCode="#[vars.httpStatus default 200]">
        <http:headers>#[vars.outboundHeaders default {}]</http:headers>
      </http:response>
      <http:error-response statusCode="#[vars.httpStatus default 500]">
        <http:body>#[payload]</http:body>
        <http:headers>#[vars.outboundHeaders default {}]</http:headers>
      </http:error-response>
    </http:listener>
    <apikit:router config-ref="api-config" />
    <error-handler>
      <on-error-propagate type="APIKIT:BAD_REQUEST">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Bad request"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">400</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
      <on-error-propagate type="APIKIT:NOT_FOUND">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Resource not found"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">404</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
      <on-error-propagate type="APIKIT:METHOD_NOT_ALLOWED">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Method not allowed"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">405</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
      <on-error-propagate type="APIKIT:NOT_ACCEPTABLE">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Not acceptable"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">406</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
      <on-error-propagate type="APIKIT:UNSUPPORTED_MEDIA_TYPE">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Unsupported media type"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">415</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
      <on-error-propagate type="APIKIT:NOT_IMPLEMENTED">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Not Implemented"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">501</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
    </error-handler>
  </flow>
  <flow name="api-console">
    <http:listener config-ref="HTTP_Listener_config" path="/console/*">
      <http:response statusCode="#[vars.httpStatus default 200]">
        <http:headers>#[vars.outboundHeaders default {}]</http:headers>
      </http:response>
      <http:error-response statusCode="#[vars.httpStatus default 500]">
        <http:body>#[payload]</http:body>
        <http:headers>#[vars.outboundHeaders default {}]</http:headers>
      </http:error-response>
    </http:listener>
    <apikit:console config-ref="api-config" />
    <error-handler>
      <on-error-propagate type="APIKIT:NOT_FOUND">
        <ee:transform>
          <ee:message>
            <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
{message: "Resource not found"}]]></ee:set-payload>
          </ee:message>
          <ee:variables>
            <ee:set-variable variableName="httpStatus">404</ee:set-variable>
          </ee:variables>
        </ee:transform>
      </on-error-propagate>
    </error-handler>
  </flow>
  <flow name="get:\users\userbyid:api-config">
    <ee:transform>
      <ee:message>
        <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
[
 {
  id: 3,
  name: "Clementine Bauch",
  username: "Samantha",
  email: "Nathan@yesenia.net",
  address: {
   street: "Douglas Extension",
   suite: "Suite 847",
   city: "McKenziehaven",
   zipcode: "59590-4157",
   geo: {
    lat: "-68.6102",
    lng: "-47.0653"
   }
  },
  phone: "1-463-123-4447",
  website: "ramiro.info",
  company: {
   name: "Romaguera-Jacobson",
   catchPhrase: "Face to face bifurcated interface",
   bs: "e-enable strategic applications"
  }
 }
]]]></ee:set-payload>
      </ee:message>
    </ee:transform>
  </flow>
  <flow name="get:\users:api-config">
    <ee:transform>
      <ee:message>
        <ee:set-payload><![CDATA[%dw 2.0
output application/json
---
[
 {
  id: 1,
  name: "Leanne Graham",
  username: "Bret",
  email: "Sincere@april.biz",
  address: {
   street: "Kulas Light",
   suite: "Apt. 556",
   city: "Gwenborough",
   zipcode: "92998-3874",
   geo: {
    lat: "-37.3159",
    lng: "81.1496"
   }
  },
  phone: "1-770-736-8031 x56442",
  website: "hildegard.org",
  company: {
   name: "Romaguera-Crona",
   catchPhrase: "Multi-layered client-server neural-net",
   bs: "harness real-time e-markets"
  }
 }
]]]></ee:set-payload>
      </ee:message>
    </ee:transform>
  </flow>
</mule>
```

## See Also
  * Error Handling Reference