AWS SAM method response

[royassis]

Hey there

Does SAM templates support method responses at this time?

[GavinZZ]

Hi there, thanks for reaching out and creating a discussion post. AWS::Serverless::Api currently do not explicitly support method response. However, a workaround is that you can define CloudFormation resource AWS::ApiGateway::Method. Here is an example provided:

Resources:
  MyApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: MyNewStageName

  MyApiGatewayRootMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      HttpMethod: GET
      AuthorizationType: NONE
      Integration:
        Type: MOCK
      ResourceId: !GetAtt MyApi.RootResourceId
      RestApiId: !Ref MyApi
      MethodResponses: <your-desired-setup>

This would allow you to use method responses along with AWS::Serverless::Api resource.

[GavinZZ]

---

An update to my response. The above answer is incorrect. I noticed that when I deploy this template using sam deploy --guided, it would fail because Resource handler returned message: "No integration defined for method.

After some investigation, this is expected behaviour according to this documentation. Unfortunately, because AWS::ApiGateway::Deployment is a generated resource, there is no simple way to add DependsOn on this generated resource.

That means there is currently no way to explicitly define a AWS::ApiGateway::Method with a SAM API resource. Will bring this issue up to team discussion.

---

Currently, the only solution is to define your custom OpenAPI definition files or use inline swagger format like

Resources:
  MyApi:
    Type: AWS::Serverless::Api
    Properties:
      StageName: prod
      DefinitionBody:
        openapi: "3.0.0"
        info:
          title: My API
          version: "1.0"
        paths:
          /my-resource:
            get:
              responses:  # <----- define this
                '200':
                  description: Successful response
                  content:
                    application/json:
                      schema:
                        type: object
                        properties:
                          id:
                            type: string
                          name:
                            type: string
                '400':
                  description: Bad Request
                  content:
                    application/json:
                      schema:
                        type: object
                        properties:
                          error:
                            type: string
              x-amazon-apigateway-integration:  # <----- define this
                type: aws_proxy  # This can be a different integration type based on your use case
                httpMethod: POST
                uri: !Sub
                  - arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${FunctionArn}/invocations
                  - FunctionArn: !GetAtt MyFunction.Arn

  MyFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: index.handler
      Runtime: nodejs14.x
      Events:
        MyApi:
          Type: Api
          Properties:
            Path: /my-resource
            Method: GET  # Specify the correct HTTP method here

[denisbog]

I would rather have a way to define the response model directly at AWS::Serverless::Function level, similar to what we have now for request model https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/sam-property-function-requestmodel.html

[Vadym79]

Any new here? With the feature of adding Amazon API Gateway REST API stages as targets for the Bedrock AgentCore Gateway method response codes becomes required as internally AgentCore Gateway calls the GetExport operation for API Gateway on our behalf to get an OpenAPI 3.0 formatted export of the API definition. It fails (among others) without at least one method response code defined. So it became a bit challenging to use the pure AWS SAM for such use cases with out defining Open API specification as shown above.