Create handle_order Lambda function

In this step, we will create a new handle_order Lambda function using a SAM template.

Preparation

1. Open template.yaml in the source code you downloaded before.

   • Comment this code block.

     # BookApiDeployment:
     #   Type: AWS::ApiGateway::Deployment
     #   Properties:
     #     RestApiId: !Ref BookApi
     #   DependsOn:
     #     - BookApiGet
     #     - BookApiCreate
     #     - BookApiDelete
     #     - LoginApi
     #     - RegisterApi
     #     - ConfirmApi
     #     - FcjCheckoutOrderApi
     #     - FcjOrderManagementApi
     
     BookApiStage:
       Type: AWS::ApiGateway::Stage
       Properties:
         RestApiId: !Ref BookApi
         StageName: !Ref stage
     #     DeploymentId: !Ref BookApiDeployment
     

     

2. Run the below commands.

   sam build
   sam validate
   sam deploy
   

   

Create FcjHandleOrder function

1. Open template.yaml in the source code you downloaded before.

   • Add the following scripts below to create FcjHandleOrder function.

     handleOrderPathPart:
       Type: String
       Default: handle
     

     

     FcjHandleOrderResource:
       Type: AWS::ApiGateway::Resource
       Properties:
         RestApiId: !Ref BookApi
         ParentId: !Ref FcjCheckoutOrderResource
         PathPart: !Ref handleOrderPathPart
     
     FcjHandleOrderFunction:
       Type: AWS::Serverless::Function
       Properties:
         CodeUri: fcj-book-shop/handle_order
         Handler: handle_order.lambda_handler
         Runtime: python3.11
         FunctionName: handle_order
         Environment:
           Variables:
             ORDER_TABLE_NAME: !Ref orderTable
             SQS_QUEUE_URL: !Ref checkoutQueueUrl
         Architectures:
           - x86_64
         Policies:
           - Statement:
               - Sid: VisualEditor0
                 Effect: Allow
                 Action:
                   - dynamodb:PutItem
                   - dynamodb:BatchWriteItem
                 Resource:
                   - !Sub "arn:aws:dynamodb:${AWS::Region}:${AWS::AccountId}:table/${orderTable}"
               - Sid: VisualEditor1
                 Effect: Allow
                 Action:
                   - sqs:*
                 Resource:
                   - !Sub "arn:aws:sqs:${AWS::Region}:${AWS::AccountId}:${checkoutQueueName}"
     
     FcjHandleOrderApiOptions:
       Type: AWS::ApiGateway::Method
       Properties:
         HttpMethod: OPTIONS
         RestApiId: !Ref BookApi
         ResourceId: !Ref FcjHandleOrderResource
         AuthorizationType: NONE
         Integration:
           Type: MOCK
           IntegrationResponses:
             - StatusCode: "200"
               ResponseParameters:
                 method.response.header.Access-Control-Allow-Origin: "'*'"
                 method.response.header.Access-Control-Allow-Methods: "'OPTIONS,POST,GET,DELETE'"
                 method.response.header.Access-Control-Allow-Headers: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"
         MethodResponses:
           - StatusCode: "200"
             ResponseParameters:
               method.response.header.Access-Control-Allow-Origin: true
               method.response.header.Access-Control-Allow-Methods: true
               method.response.header.Access-Control-Allow-Headers: true
     
     FcjHandleOrderApi:
       Type: AWS::ApiGateway::Method
       Properties:
         HttpMethod: POST
         RestApiId: !Ref BookApi
         ResourceId: !Ref FcjHandleOrderResource
         AuthorizationType: NONE
         Integration:
           Type: AWS_PROXY
           IntegrationHttpMethod: POST # For Lambda integrations, you must set the integration method to POST
           Uri: !Sub >-
             arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${FcjHandleOrderFunction.Arn}/invocations
         MethodResponses:
           - StatusCode: "200"
             ResponseParameters:
               method.response.header.Access-Control-Allow-Origin: true
               method.response.header.Access-Control-Allow-Methods: true
               method.response.header.Access-Control-Allow-Headers: true
     
     FcjHandleOrderApiInvokePermission:
       Type: AWS::Lambda::Permission
       Properties:
         FunctionName: !Ref FcjHandleOrderFunction
         Action: lambda:InvokeFunction
         Principal: apigateway.amazonaws.com
         SourceAccount: !Ref "AWS::AccountId"
     

     

2. The directory structure is as follows.

   fcj-book-shop-sam-ws3
   ├── fcj-book-shop
   │   ├── checkout_order
   │   │   └── checkout_order.py
   │   ├── order_management
   │   │   └── order_management.py
   │   ├── handle_order
   │   │   └── handle_order.py
   │   ├── ...
   │
   └── template.yaml
   

   • Create handle_order folder in fcj-book-shop-sam-ws6/fcj-book-shop/ folder.

   • Create handle_order.py file and copy the following code to it.

     import json
     import boto3
     import os
     
     headers = {
         "Content-Type": "application/json",
         "Access-Control-Allow-Origin": "*",
         "Access-Control-Allow-Methods": "OPTIONS,POST,GET,DELETE",
         "Access-Control-Allow-Headers": "Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token"
     }
     
     dynamodb = boto3.resource('dynamodb')
     sqs = boto3.client('sqs')
     
     # Define the DynamoDB table name and SQS queue URL
     table_name = os.getenv('ORDER_TABLE_NAME')
     queue_url = os.getenv('SQS_QUEUE_URL')
     
     
     def lambda_handler(event, context):
         # Get product body info from the event
         products = json.loads(event['body'])
         books = products['books']
         receipt_handle = products['receiptHandle']
     
         # Write product info to DynamoDB
         table = dynamodb.Table(table_name)
         try:
             for book in books:
                 data = {
                     'id': products['id'],
                     'book_id': book['id'],
                     'name': book['name'],
                     'qty': book['qty'],
                     'price': str(products['price'])
                 }
     
                 table.put_item(Item=data)
         except Exception as e:
             print(f"Error writing to DynamoDB: {e}")
             raise Exception(f"Error writing to DynamoDB: {e}")
     
         # Delete message in SQS
         try:
             sqs.delete_message(
                 QueueUrl=queue_url,
                 ReceiptHandle=receipt_handle
             )
         except Exception as e:
             print(f"Error deleting message from SQS: {e}")
             raise Exception(f"Error deleting message from SQS: {e}")
     
         return {
             'statusCode': 200,
             'headers': headers,
             'body': json.dumps('Order processed successfully')
         }
     

     

3. Uncomment this code block.

   BookApiDeployment:
     Type: AWS::ApiGateway::Deployment
     Properties:
       RestApiId: !Ref BookApi
     DependsOn:
       - BookApiGet
       - BookApiCreate
       - BookApiDelete
       - LoginApi
       - RegisterApi
       - ConfirmApi
       - FcjCheckoutOrderApi
       - FcjOrderManagementApi
       - FcjHandleOrderApi
   
   BookApiStage:
     Type: AWS::ApiGateway::Stage
     Properties:
       RestApiId: !Ref BookApi
       StageName: !Ref stage
       DeploymentId: !Ref BookApiDeployment
   

   

4. Run the below commands.

   sam build
   sam validate
   sam deploy
   

   

Check the creation

1. Open Amazon API Gateway console.

   • Click fcj-serverless-api.
   • Click Resources on the left menu.
   • Check /handle just created.

2. Open Amazon Lambda console.

   • Click Functions on the left menu.
   • Choose handle_order function.
   • At handle_order page, check the function that just created.