Customized response example for Amazon SAM

You can customize some API Gateway error responses by defining response headers within your Amazon SAM template. To do this, you use the Gateway Response Object data type.

The following is an example Amazon SAM template that creates a customized response for the DEFAULT_5XX error.

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
  MyApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: Prod
      GatewayResponses:
        DEFAULT_5XX:
          ResponseParameters:
            Headers:
              Access-Control-Expose-Headers: "'WWW-Authenticate'"
              Access-Control-Allow-Origin: "'*'"
              ErrorHeader: "'MyCustomErrorHeader'"
          ResponseTemplates:
            application/json: "{\"message\": \"Error on the $context.resourcePath resource\" }"
              
  GetFunction:
    Type: AWS::Serverless::Function
    Properties:
      Runtime: python3.10
      Handler: index.handler
      InlineCode: |
        def handler(event, context):
          raise Exception('Check out the new response!')
      Events:
        GetResource:
          Type: Api
          Properties:
            Path: /error
            Method: get
            RestApiId: !Ref MyApi

For more information about API Gateway responses, see Gateway responses in API Gateway in the API Gateway Developer Guide.