Example 1: Override the status code based on the integration body Example 2: Override the request header and create new headers

Override your API's request and response parameters and status codes for REST APIs in API Gateway

You can use mapping template transformations to override any type of request parameter, response header, or response status code. You use a mapping template to do the following:

Perform many-to-one parameter mappings
Override parameters after standard API Gateway mappings have been applied
Conditionally map parameters based on body content or other parameter values
Programmatically create new parameters
Override status codes returned by your integration endpoint

Overrides are final. An override may only be applied to each parameter once. If you try to override the same parameter multiple times, API Gateway returns a 5XX response. If you must override the same parameter multiple times throughout the template, we recommend creating a variable and applying the override at the end of the template. The template is applied only after the entire template is parsed.

Example 1: Override the status code based on the integration body

The following example use the example API to override the status code based on the integration response body.

AWS Management Console

To override a status code based on the integration response body

Sign in to the API Gateway console at https://console.aws.amazon.com/apigateway.
Choose Create API.
For REST API, choose Build.
For API details, choose Example API.
Choose Create API.

API Gateway creates an example pet store API. To retrieve information about a pet, you use the API method request of GET /pets/{petId}, where {petId} is a path parameter corresponding to an ID number for a pet.

In this example, you override the GET method's response code to 400 when an error condition is detected.
In the Resources tree, choose the GET method under /{petId}.
First, you test the current implementation of the API.

Choose the Test tab. You might need to choose the right arrow button to show the tab.
For petId, enter -1, and then choose Test.

The Response body indicates an out-of-range error:
```
{
  "errors": [
    {
      "key": "GetPetRequest.petId",
      "message": "The value is out of range."
    }
  ]
}
```
In addition, the last line under Logs ends with: Method completed with status: 200.

The integration was completed successfully, but there was an error. Now you'll override the status code based on the integration response.
On the Integration response tab, for the Default - Response, choose Edit.
Choose Mapping templates.
Choose Add mapping template.
For Content type, enter application/json.
For Template body, enter the following:
```
#set($inputRoot = $input.path('$'))
$input.json("$")
#if($inputRoot.toString().contains("error"))
#set($context.responseOverride.status = 400)
#end
```
This mapping template uses the $context.responseOverride.status variable to override the status code to 400 if the integration response contains the string error.
Choose Save.
Choose the Test tab.
For petId, enter -1.
In the results, the Response Body indicates an out-of-range error:
```
{
  "errors": [
    {
      "key": "GetPetRequest.petId",
      "message": "The value is out of range."
    }
  ]
}
```
However, the last line under Logs now ends with: Method completed with status: 400.

AWS CloudFormation

In this example, you use the body property to import an OpenAPI definition file into API Gateway.


AWSTemplateFormatVersion: 2010-09-09
Resources:
  Api:
    Type: 'AWS::ApiGateway::RestApi'
    Properties:
      Body: 
        openapi: 3.0.1
        info:
          title: PetStore Example 1
          description: Example pet store API.
          version: "2025-01-14T00:13:18Z"
        paths:
          /pets/{petId}:
            get:
              parameters:
                - name: petId
                  in: path
                  required: true
                  schema:
                    type: string
              responses:
                "200":
                  description: 200 response
              x-amazon-apigateway-integration:
                httpMethod: GET
                uri: http://petstore.execute-api.us-east-1.amazonaws.com/petstore/pets/{petId}
                responses:
                  default:
                    statusCode: "200"
                    responseTemplates:
                      application/json: |-
                        #set($inputRoot = $input.path('$'))
                        $input.json("$")
                        #if($inputRoot.toString().contains("error"))
                        #set($context.responseOverride.status = 400)
                        #end
                requestParameters:
                  integration.request.path.petId: method.request.path.petId
                passthroughBehavior: when_no_match
                type: http
        components:
          schemas:
            Pet:
              type: object
              properties:
                id:
                  type: integer
                type:
                  type: string
                price:
                  type: number
  ApiGatewayDeployment:
    Type: 'AWS::ApiGateway::Deployment'
    DependsOn: Api 
    Properties: 
      RestApiId: !Ref Api
  ApiGatewayDeployment20250219:
    Type: 'AWS::ApiGateway::Deployment'
    DependsOn: Api 
    Properties: 
      RestApiId: !Ref Api
  Stage:
    Type: 'AWS::ApiGateway::Stage'
    Properties:
       DeploymentId: !Ref ApiGatewayDeployment20250219
       RestApiId: !Ref Api
       StageName: prod

OpenAPI

The following OpenAPI definition creates the GET pets/{petId} resource and overrides the status code based on the integration body.


{
  "openapi" : "3.0.1",
  "info" : {
    "title" : "PetStore Example 1",
    "description" : "Example pet store API.",
    "version" : "2025-01-14T00:13:18Z"
  },
  "paths" : {
    "/pets/{petId}" : {
      "get" : {
        "parameters" : [ {
          "name" : "petId",
          "in" : "path",
          "required" : true,
          "schema" : {
            "type" : "string"
          }
        } ],
        "responses" : {
          "200" : {
            "description" : "200 response"
          }
        },
        "x-amazon-apigateway-integration" : {
          "httpMethod" : "GET",
          "uri" : "http://petstore.execute-api.us-east-1.amazonaws.com/petstore/pets/{petId}",
          "responses" : {
            "default" : {
              "statusCode" : "200",
              "responseTemplates" : {
                "application/json" : "#set($inputRoot = $input.path('$'))\n$input.json(\"$\")\n#if($inputRoot.toString().contains(\"error\"))\n#set($context.responseOverride.status = 400)\n#end"
              }
            }
          },
          "requestParameters" : {
            "integration.request.path.petId" : "method.request.path.petId"
          },
          "passthroughBehavior" : "when_no_match",
          "type" : "http"
        }
      }
    }
  },
  "components" : {
    "schemas" : {
      "Pet" : {
        "type" : "object",
        "properties" : {
          "id" : {
            "type" : "integer"
          },
          "type" : {
            "type" : "string"
          },
          "price" : {
            "type" : "number"
          }
        }
      }
    }
  }
}

Example 2: Override the request header and create new headers

The following example uses the example API to override the request header and create new headers.

AWS Management Console

To override a method's request header by creating a new header

Sign in to the API Gateway console at https://console.aws.amazon.com/apigateway.
Choose the example API you created in the previous tutorial. The name of the API should be PetStore.
In the Resources tree, choose the GET method under /pet.
On the Method request tab, for Method request settings, choose Edit.
Choose HTTP request headers, and then choose Add header.
For Name, enter header1.
Choose Add header, and then create a second header called header2.
Choose Save.

Now, you combine these headers into one header value using a mapping template.
On the Integration request tab, for Integration request settings, choose Edit.
For Request body passthrough, select When there are no templates defined (recommended).

Choose Mapping templates, and then do the following:

Choose Add mapping template.
For Content type, enter application/json.

For Template body, enter the following:


#set($header1Override = "pets")
#set($header3Value = "$input.params('header1')$input.params('header2')")
$input.json("$")
#set($context.requestOverride.header.header3 = $header3Value)
#set($context.requestOverride.header.header1 = $header1Override)
#set($context.requestOverride.header.multivalueheader=[$header1Override, $header3Value])

This mapping template overrides header1 with the string pets and creates a multi-value header called $header3Value that combines header1 and header2.

Choose Save.
Choose the Test tab.
Under Headers, copy the following code:
```
header1:header1Val
header2:header2Val
```

Choose Test.

In the Logs, you should see an entry that includes this text:


Endpoint request headers: {header3=header1Valheader2Val, 
header2=header2Val, header1=pets, x-amzn-apigateway-api-id=api-id,
Accept=application/json, multivalueheader=pets,header1Valheader2Val}

AWS CloudFormation

In this example, you use the body property to import an OpenAPI definition file into API Gateway.


AWSTemplateFormatVersion: 2010-09-09
Resources:
  Api:
    Type: 'AWS::ApiGateway::RestApi'
    Properties:
      Body: 
        openapi: 3.0.1
        info:
          title: PetStore Example 2
          description: Example pet store API.
          version: "2025-01-14T00:36:18Z"
        paths:
          /pets:
            get:
              parameters:
                - name: header2
                  in: header
                  schema:
                    type: string
                - name: page
                  in: query
                  schema:
                    type: string
                - name: type
                  in: query
                  schema:
                    type: string
                - name: header1
                  in: header
                  schema:
                    type: string
              responses:
                "200":
                  description: 200 response
              x-amazon-apigateway-integration:
                httpMethod: GET
                uri: http://petstore.execute-api.us-east-1.amazonaws.com/petstore/pets
                responses:
                  default:
                    statusCode: "200"
                requestParameters:
                  integration.request.header.header1: method.request.header.header1
                  integration.request.header.header2: method.request.header.header2
                  integration.request.querystring.page: method.request.querystring.page
                  integration.request.querystring.type: method.request.querystring.type
                requestTemplates:
                  application/json: |-
                    #set($header1Override = "pets")
                    #set($header3Value = "$input.params('header1')$input.params('header2')")
                    $input.json("$")
                    #set($context.requestOverride.header.header3 = $header3Value)
                    #set($context.requestOverride.header.header1 = $header1Override)
                    #set($context.requestOverride.header.multivalueheader=[$header1Override, $header3Value])
                passthroughBehavior: when_no_match
                type: http
        components:
          schemas:
            Pet:
              type: object
              properties:
                id:
                  type: integer
                type:
                  type: string
                price:
                  type: number
  ApiGatewayDeployment:
    Type: 'AWS::ApiGateway::Deployment'
    DependsOn: Api 
    Properties: 
      RestApiId: !Ref Api
  ApiGatewayDeployment20250219:
    Type: 'AWS::ApiGateway::Deployment'
    DependsOn: Api 
    Properties: 
      RestApiId: !Ref Api
  Stage:
    Type: 'AWS::ApiGateway::Stage'
    Properties:
       DeploymentId: !Ref ApiGatewayDeployment20250219
       RestApiId: !Ref Api
       StageName: prod

OpenAPI

The following OpenAPI definition creates the GET pets resource and overrides the request header and create new headers.


{
  "openapi" : "3.0.1",
  "info" : {
    "title" : "PetStore Example 2",
    "description" : "Example pet store API.",
    "version" : "2025-01-14T00:36:18Z"
  },
  "paths" : {
    "/pets" : {
      "get" : {
        "parameters" : [ {
          "name" : "header2",
          "in" : "header",
          "schema" : {
            "type" : "string"
          }
        }, {
          "name" : "page",
          "in" : "query",
          "schema" : {
            "type" : "string"
          }
        }, {
          "name" : "type",
          "in" : "query",
          "schema" : {
            "type" : "string"
          }
        }, {
          "name" : "header1",
          "in" : "header",
          "schema" : {
            "type" : "string"
          }
        } ],
        "responses" : {
          "200" : {
            "description" : "200 response"
          }
        },
        "x-amazon-apigateway-integration" : {
          "httpMethod" : "GET",
          "uri" : "http://petstore.execute-api.us-east-1.amazonaws.com/petstore/pets",
          "responses" : {
            "default" : {
              "statusCode" : "200"
            }
          },
          "requestParameters" : {
            "integration.request.header.header1" : "method.request.header.header1",
            "integration.request.header.header2" : "method.request.header.header2",
            "integration.request.querystring.page" : "method.request.querystring.page",
            "integration.request.querystring.type" : "method.request.querystring.type"
          },
          "requestTemplates" : {
            "application/json" : "#set($header1Override = \"pets\")\n#set($header3Value = \"$input.params('header1')$input.params('header2')\")\n$input.json(\"$\")\n#set($context.requestOverride.header.header3 = $header3Value)\n#set($context.requestOverride.header.header1 = $header1Override)\n#set($context.requestOverride.header.multivalueheader=[$header1Override, $header3Value])"
          },
          "passthroughBehavior" : "when_no_match",
          "type" : "http"
        }
      }
    }
  }
}

To use a mapping template override, add one or more of the following $context variables. For a list of $context variables, see Context variables for data transformations.

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Additional mapping template example

Tutorial: Modify the integration request and response for integrations to AWS services