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Getting started with Amazon SAM and the Amazon CDK

This topic describes what you need to use the Amazon SAM CLI with Amazon CDK applications, and provides instructions for building and locally testing a simple Amazon CDK application.

Prerequisites

To use the Amazon SAM CLI with Amazon CDK, you must install the Amazon CDK, and the Amazon SAM CLI.

Creating and locally testing an Amazon CDK application

To locally test an Amazon CDK application using the Amazon SAM CLI, you must have an Amazon CDK application that contains a Lambda function. Use the following steps to create a basic Amazon CDK application with a Lambda function. For more information, see Creating a serverless application using the Amazon CDK in the Amazon Cloud Development Kit (Amazon CDK) Developer Guide.

Step 1: Create an Amazon CDK application

For this tutorial, initialize an Amazon CDK application that uses TypeScript.

Command to run:

Amazon CDK v2

mkdir cdk-sam-example
cd cdk-sam-example
cdk init app --language typescript

Amazon CDK v1

mkdir cdk-sam-example
cd cdk-sam-example
cdk init app --language typescript
npm install @aws-cdk/aws-lambda

Step 2: Add a Lambda function to your application

Replace the code in lib/cdk-sam-example-stack.ts with the following:

Amazon CDK v2

import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as lambda from 'aws-cdk-lib/aws-lambda';

export class CdkSamExampleStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    new lambda.Function(this, 'MyFunction', {
      runtime: lambda.Runtime.PYTHON_3_9,
      handler: 'app.lambda_handler',
      code: lambda.Code.fromAsset('./my_function'),
    });
  }
}

Amazon CDK v1

import * as cdk from '@aws-cdk/core';
import * as lambda from '@aws-cdk/aws-lambda';

export class CdkSamExampleStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    new lambda.Function(this, 'MyFunction', {
      runtime: lambda.Runtime.PYTHON_3_9,
      handler: 'app.lambda_handler',
      code: lambda.Code.fromAsset('./my_function'),
    });
  }
}

Step 3: Add your Lambda function code

Create a directory named my_function. In that directory, create a file named app.py.

Command to run:

mkdir my_function
cd my_function
touch app.py

Add the following code to app.py:

def lambda_handler(event, context):
    return "Hello from SAM and the CDK!"

Step 4: Test your Lambda function

You can use the Amazon SAM CLI to locally invoke a Lambda function that you define in an Amazon CDK application. To do this, you need the function construct identifier and the path to your synthesized Amazon CloudFormation template.

Command to run:

cdk synth --no-staging

sam local invoke MyFunction --no-event -t ./cdk.out/CdkSamExampleStack.template.json

Example output:

Invoking app.lambda_handler (python3.9)
     
START RequestId: 5434c093-7182-4012-9b06-635011cac4f2 Version: $LATEST
"Hello from SAM and the CDK!"
END RequestId: 5434c093-7182-4012-9b06-635011cac4f2
REPORT RequestId: 5434c093-7182-4012-9b06-635011cac4f2	Init Duration: 0.32 ms	Duration: 177.47 ms	Billed Duration: 178 ms	Memory Size: 128 MB	Max Memory Used: 128 MB

For more information about options available to test Amazon CDK applications using the Amazon SAM CLI, see Locally testing Amazon CDK applications.