README.md

Simplest Possible, BCE structured, AWS Lambda Function with Cloud Development Kit (CDK) Boilerplate

A lean starting point for building, testing and deploying AWS Lambdas with Java. This project serves as a reference implementation for serverless BCE (Boundary-Control-Entity) architecture.

TL;DR

A simple Java AWS Lambda without any AWS dependencies:

package airhacks.lambda.example.boundary;

public class EventListener {

    static String message = System.getenv("message");

    public void onEvent(Object awsEvent) {
        Log.info("event received: %s", awsEvent);
        var domainEvent = extract(awsEvent);
        EventProcessor.process(domainEvent);
    }

    static ExampleEvent extract(Object event) {
        return new ExampleEvent(event.toString());
    }
}

...deployed with AWS Cloud Development Kit:

import software.amazon.awscdk.services.lambda.*;

Function createFunction(String functionName, String functionHandler, Map<String,String> configuration, int memory, int timeout) {
    return Function.Builder.create(this, functionName)
            .runtime(Runtime.JAVA_21)
            .architecture(Architecture.ARM_64)
            .code(Code.fromAsset("../lambda/target/function.jar"))
            .handler(functionHandler)
            .memorySize(memory)
            .functionName(functionName)
            .environment(configuration)
            .timeout(Duration.seconds(timeout))
            .tracing(Tracing.ACTIVE)
            .build();
}

...provisioned with maven and cdk:

cd lambda && mvn clean package
cd ../cdk && mvn clean package && cdk deploy

...and (blackbox) tested with AWS SDK for Java 2.x:

@BeforeEach
public void initClient() {
    var credentials = DefaultCredentialsProvider.builder().build();
    this.client = LambdaClient.builder()
                    .credentialsProvider(credentials)
                    .build();
}

@Test
public void invokeLambdaAsynchronously() {
    var json = """
            {
                    "user":"duke"
            }
                    """;
    var payload = SdkBytes.fromUtf8String(json);

    var request = InvokeRequest.builder()
                    .functionName("airhacks_EventListener")
                    .payload(payload)
                    .invocationType(InvocationType.REQUEST_RESPONSE)
                    .build();

    var response = this.client.invoke(request);
    var error = response.functionError();
    assertNull(error);
    var value = response.payload().asUtf8String();
    Log.info("Function executed. Response: " + value);
}

In Action

Java "vs." JavaScript

Cold and "warm" starts of JavaScript and Java Lambdas:

AWS Lambda on Java: How Good / Bad Is The Cold Start?

Lambda Configuration

References

The deployment is borrowed from: "Slightly Streamlined AWS Cloud Development Kit (CDK) Boilerplate"