AWS Lambda Java Examples

This project demonstrates the creation of AWS Lambda functions in Java, showcasing various examples using custom annotations to define Lambda handlers.

Project Structure

• lambdas-sidecar: Contains common utilities and configurations shared across Lambda functions.
• lambda-examples: Contains example implementations of AWS Lambda functions using Java and custom annotations.

Requirements

• Java 17
• Gradle
• AWS CLI
• AWS CDK

Getting Started

Clone the Repository

git clone <repository-url>
cd my-aws-infra

Build the Project

./gradlew clean build

Set Up AWS CLI

Install AWS CLI using Homebrew:

brew install awscli

Configure AWS credentials:

aws configure --profile your-account

Deploy with AWS CDK

Ensure that AWS CDK is installed:

npm install -g aws-cdk

Bootstrap your environment:

cdk bootstrap --profile your-account

Synthesize and deploy the CDK stack:

cdk synth --profile your-account
cdk deploy --profile your-account

Example Usage

Custom Annotations

The project uses custom annotations to define the Lambda handlers, simplifying the process of creating and managing Lambda functions. Here are some of the examples:

@LambdaFunction(contentType = "text/plain")
public String getPlainText() {
    return "Text example";
}

@LambdaFunction(statusCode = 201, contentType = "text/plain")
public String getPlainTextCreatedExample() {
    return "Example 2";
}

@LambdaFunction()
@PathTemplate("/{name}/{age}")
public ResponseEntity<ExampleResponseDto> greetUserByNameAndAge(@PathParam("name") String name, @PathParam("age") int age) {
    return ResponseEntity.<ExampleResponseDto> builder()
            .body(new ExampleResponseDto("Hello, " + name + "! You are " + age + " years old."))
            .build();
}

@LambdaFunction()
public ResponseEntity<ExampleResponseDto> handleRequestHeaders(@RequestHeader("Authorization") String authToken) {
    if (authToken != null && authToken.equals("Bearer abc123")) {
        return ResponseEntity.<ExampleResponseDto>builder()
                .body(new ExampleResponseDto("Token is valid"))
                .build();
    } else {
        return ResponseEntity.<ExampleResponseDto>builder()
                .statusCode(401)
                .body(new ExampleResponseDto("Unauthorized"))
                .build();
    }
}

@LambdaFunction()
public ResponseEntity<List<ExampleResponseDto>> processJsonArrayResponseEntity(@RequestBody List<Map<String, Object>> input) {
    List<ExampleResponseDto> responses = input.stream()
            .map(item -> new ExampleResponseDto("Hello, " + item.get("name") + "!"))
            .collect(Collectors.toList());

    return ResponseEntity.<List<ExampleResponseDto>>builder()
            .body(responses)
            .build();
}

@LambdaFunction()
public List<ExampleResponseDto> processJsonArray(@RequestBody List<Map<String, Object>> input) {
    return input.stream()
            .map(item -> new ExampleResponseDto("Hello, " + item.get("name") + "!"))
            .collect(Collectors.toList());
}

Lambda Configuration

The configuration for Lambda functions is stored in resources/lambdas-config.yaml:

lambdas:
  - name: "ExampleFunction"
    handler: "kz.bkudaibergenov.aws.examples.lambda.LambdaPlainText::handleRequest"
    codePath: "./lambda-examples/build/libs/example-lambda.jar"
    api:
      name: "ExampleApi"
      path: "/example"
      methods: ["GET", "POST"]

Examples Included

1. Plain Text Response

   • Simple Lambda function returning plain text.

2. JSON Response

   • Lambda function returning a JSON response using ExampleResponseDto.

3. Path Parameters

   • Example demonstrating handling of path parameters using @PathTemplate.

4. Request Headers

   • Example demonstrating validation of authorization tokens using @RequestHeader.

5. Redirects

   • Example returning a 302 redirect with a Location header.

6. File Download

   • Example for downloading a file with proper Content-Disposition.

7. Processing JSON Arrays

   • Lambda function that processes JSON arrays and returns a list of DTOs.

How to Run

You can run the application locally for testing:

./gradlew run