Transforming API requests and responses - Amazon API Gateway

Transforming API requests and responses

You can modify API requests from clients before they reach your backend integrations. You can also change the response from integrations before API Gateway returns the response to clients. You use parameter mapping to modify API requests and responses for HTTP APIs. To use parameter mapping, you specify API request or response parameters to modify, and specify how to modify those parameters.

Transforming API requests

You use request parameters to change requests before they reach your backend integrations. You can modify headers, query strings, the request path, or the request body.

Request parameters are a key-value map. The key identifies the location of the request parameter to change, and how to change it. The value specifies the new data for the parameter.

The following table shows supported keys.

Parameter mapping keys
Type Syntax
Header append|overwrite|remove:header.headername
Query string append|overwrite|remove:querystring.querystring-name
Path overwrite:path

The following table shows supported values that you can map to parameters.

Request parameter mapping values
Type Syntax Notes
Header value $request.header.name Header names are case-insensitive. API Gateway combines multiple header values with commas, for example "header1": "value1,value2". Some headers are reserved. To learn more, see Reserved headers.
Query string value $request.querystring.name Query string names are case-sensitive. API Gateway combines multiple values with commas, for example "querystring1" "Value1,Value2".
Request body $request.body.name A JSON path expression. Recursive descent ($request.body..name) and filter expressions (?(expression)) aren't supported.
Note

When you specify a JSON path, API Gateway truncates the request body at 100 KB and then applies the selection expression. To send payloads larger than 100 KB, specify $request.body.

Request path $request.path The request path, without the stage name.
Path parameter $request.path.name The value of a path parameter in the request. For example if the route is /pets/{petId}, you can map the petId parameter from the request with $request.path.petId.
Context variable $context.variableName The value of a context variable.
Stage variable $stageVariables.variableName The value of a stage variable.
Static value string A constant value.

Transforming API responses

You use response parameters to transform the HTTP response from a backend integration before returning the response to clients. You can modify headers or the status code of a response before API Gateway returns the response to clients.

You configure response parameters for each status code that your integration returns. Response parameters are a key-value map. The key identifies the location of the request parameter to change, and how to change it. The value specifies the new data for the parameter.

The following table shows supported keys.

Response parameter mapping keys
Type Syntax
Header append|overwrite|remove:header.headername
Status code overwrite:statuscode

The following table shows supported values that you can map to parameters.

Response parameter mapping values
Type Syntax Notes
Header value $request.header.name Header names are case-insensitive. API Gateway combines multiple header values with commas, for example "header1": "value1,value2". Some headers are reserved. To learn more, see Reserved headers.
Response body $response.body.name A JSON path expression. Recursive descent ($response.body..name) and filter expressions (?(expression)) aren't supported.
Note

When you specify a JSON path, API Gateway truncates the response body at 100 KB and then applies the selection expression. To send payloads larger than 100 KB, specify $response.body.

Context variable $context.variableName The value of a supported context variable.
Stage variable $stageVariables.variableName The value of a stage variable.
Static value string A constant value.

Reserved headers

The following headers are reserved. You can't configure request or response mappings for these headers.

  • access-control-*

  • apigw-*

  • Authorization

  • Connection

  • Content-Encoding

  • Content-Length

  • Content-Location

  • Forwarded

  • Keep-Alive

  • Origin

  • Proxy-Authenticate

  • Proxy-Authorization

  • TE

  • Trailers

  • Transfer-Encoding

  • Upgrade

  • x-amz-*

  • x-amzn-*

  • X-Forwarded-For

  • X-Forwarded-Host

  • X-Forwarded-Proto

  • Via

Examples

The following AWS CLI examples configure parameter mappings. For example AWS CloudFormation templates, see GitHub.

Add a header to an API request

The following example adds a header named header1 to an API request before it reaches your backend integration. API Gateway populates the header with the request ID.

aws apigatewayv2 create-integration \ --api-id abcdef123 \ --integration-type HTTP_PROXY \ --payload-format-version 1.0 \ --integration-uri 'https://api.example.com' \ --integration-method ANY \ --request-parameters '{ "append:header.header1": "$context.requestId" }'

Rename a request header

The following example renames a request header from header1 to header2.

aws apigatewayv2 create-integration \ --api-id abcdef123 \ --integration-type HTTP_PROXY \ --payload-format-version 1.0 \ --integration-uri 'https://api.example.com' \ --integration-method ANY \ --request-parameters '{ "append:header.header2": "$request.header.header1", "remove:header.header1": "''"}' }

Change the response from an integration

The following example configures response parameters for an integration. When the integrations returns a 500 status code, API Gateway changes the status code to 403, and adds header11 to the response. When the integration returns a 404 status code, API Gateway adds an error header to the response.

aws apigatewayv2 create-integration \ --api-id abcdef123 \ --integration-type HTTP_PROXY \ --payload-format-version 1.0 \ --integration-uri 'https://api.example.com' \ --integration-method ANY \ --response-parameters '{"500" : {"append:header.header1": "$context.requestId", "overwrite:statuscode" : "403"}, "404" : {"append:header.error" : "$stageVariables.environmentId"} }

Remove configured parameter mappings

The following example command removes previously configured request parameters for append:header.header1. It also removes previously configured response parameters for a 200 status code.

aws apigatewayv2 update-integration \ --api-id abcdef123 \ --integration-type HTTP_PROXY \ --payload-format-version 1.0 \ --integration-uri 'https://api.example.com' \ --integration-method ANY \ --request-parameters {"append:header.header1" : ""} \ --response-parameters {"200" : {}}