Request and response mapping in AWS - Mini Project: Build & Apply

AWS API Gateway Request and Response Mapping

📖 Scenario: You are building a simple API using AWS API Gateway. Your API will receive requests and send responses. To control how data is passed between the client and backend, you need to create request and response mapping templates.This helps transform the data format so your backend gets exactly what it expects, and your client receives the right response.

🎯 Goal: Create an AWS API Gateway method with request and response mapping templates that transform JSON data between client and backend.

📋 What You'll Learn

Create a REST API resource called /items

Add a POST method to /items

Configure a request mapping template to extract itemName and itemQuantity from the incoming JSON body and pass them as JSON to the backend

Configure a response mapping template to transform the backend JSON response to include a message and statusCode

Use valid AWS API Gateway mapping template syntax

💡 Why This Matters

🌍 Real World

API Gateway request and response mapping is used to control data flow between clients and backend services, ensuring data formats match expectations.

💼 Career

Understanding request and response mapping is essential for cloud architects and developers building serverless APIs on AWS.

1

Create the API resource and POST method

Create a REST API resource called /items and add a POST method to it in AWS API Gateway.

AWS

# Your code here to create /items resource and POST method

Need a hint?

Use AWS CloudFormation syntax to define the resource and method.

2

Add request mapping template

Add a request mapping template to the POST method integration that extracts itemName and itemQuantity from the incoming JSON body and passes them as JSON to the backend.

AWS

Resources:
  ItemsResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      ParentId: !GetAtt ApiGatewayRestApi.RootResourceId
      PathPart: items
      RestApiId: !Ref ApiGatewayRestApi

  ItemsPostMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      HttpMethod: POST
      ResourceId: !Ref ItemsResource
      RestApiId: !Ref ApiGatewayRestApi
      AuthorizationType: NONE
      Integration:
        Type: MOCK
        RequestTemplates:
          application/json: |
            # Your mapping template here

Need a hint?

Use $input.path to extract JSON fields in the mapping template.

3

Add response mapping template

Add a response mapping template to the POST method integration that transforms the backend JSON response to include a message and statusCode fields.

AWS

Resources:
  ItemsResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      ParentId: !GetAtt ApiGatewayRestApi.RootResourceId
      PathPart: items
      RestApiId: !Ref ApiGatewayRestApi

  ItemsPostMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      HttpMethod: POST
      ResourceId: !Ref ItemsResource
      RestApiId: !Ref ApiGatewayRestApi
      AuthorizationType: NONE
      Integration:
        Type: MOCK
        RequestTemplates:
          application/json: |
            {
              "itemName": "$input.path('$.itemName')",
              "itemQuantity": $input.path('$.itemQuantity')
            }
        IntegrationResponses:
          - StatusCode: 200
            ResponseTemplates:
              application/json: |
                # Your response mapping template here

Need a hint?

Use IntegrationResponses and ResponseTemplates to define the response mapping.

4

Complete the method response configuration

Add the method response configuration for status code 200 to complete the POST method setup.

AWS

Resources:
  ItemsResource:
    Type: AWS::ApiGateway::Resource
    Properties:
      ParentId: !GetAtt ApiGatewayRestApi.RootResourceId
      PathPart: items
      RestApiId: !Ref ApiGatewayRestApi

  ItemsPostMethod:
    Type: AWS::ApiGateway::Method
    Properties:
      HttpMethod: POST
      ResourceId: !Ref ItemsResource
      RestApiId: !Ref ApiGatewayRestApi
      AuthorizationType: NONE
      Integration:
        Type: MOCK
        RequestTemplates:
          application/json: |
            {
              "itemName": "$input.path('$.itemName')",
              "itemQuantity": $input.path('$.itemQuantity')
            }
        IntegrationResponses:
          - StatusCode: 200
            ResponseTemplates:
              application/json: |
                {
                  "message": "Item processed successfully",
                  "statusCode": 200
                }
      MethodResponses:
        - StatusCode: 200
          ResponseModels:
            application/json: "Empty"  # Your method response here

Need a hint?

MethodResponses define what the client receives. Use status code 200 and response model "Empty".