Table of Contents

Deploy a Micronaut application to AWS Lambda Java 17 Runtime

Learn how to distribute a Micronaut application to AWS Lambda 17 Runtime

Authors: Sergio del Amo

Micronaut Version: 4.6.3

1. Getting Started

In this guide, we will create a Micronaut application written in Java.

2. What you will need

To complete this guide, you will need the following:

3. Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

4. Writing the Application

Create an application using the Micronaut Command Line Interface or with Micronaut Launch.

mn create-app example.micronaut.micronautguide \
    --features=aws-lambda,amazon-api-gateway \
    --build=maven \
    --lang=java \
    --test=junit
If you don’t specify the --build argument, Gradle with the Kotlin DSL is used as the build tool.
If you don’t specify the --lang argument, Java is used as the language.
If you don’t specify the --test argument, JUnit is used for Java and Kotlin, and Spock is used for Groovy.

The previous command creates a Micronaut application with the default package example.micronaut in a directory named micronautguide.

If you use Micronaut Launch, select Micronaut Application as application type and add aws-lambda, and amazon-api-gateway features.

If you have an existing Micronaut application and want to add the functionality described here, you can view the dependency and configuration changes from the specified features, and apply those changes to your application.

Diff

Setup IntelliJ IDEA to develop Micronaut Applications.

The generated application contains a HomeController. It responds to POST requests to /.

src/main/java/example/micronaut/HomeController.java
package example.micronaut;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import java.util.Collections;
import java.util.Map;

@Controller
public class HomeController {

    @Get
    public Map<String, Object> index() {
        return Collections.singletonMap("message", "Hello World");
    }
}
1 The class is defined as a controller with the @Controller annotation mapped to the path /.
2 The @Get annotation maps the index method to an HTTP GET request on /.

The generated tests illustrates how the code works when the lambda gets invoked:

src/test/java/example/micronaut/HomeControllerTest.java
package example.micronaut;
import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
import io.micronaut.function.aws.proxy.payload1.ApiGatewayProxyRequestEventFunction;
import io.micronaut.function.aws.proxy.MockLambdaContext;
import io.micronaut.http.HttpMethod;
import io.micronaut.http.HttpStatus;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertEquals;

class HomeControllerTest {
    private static ApiGatewayProxyRequestEventFunction handler;

    @BeforeAll
    static void setupSpec() {
        handler = new ApiGatewayProxyRequestEventFunction();
    }
    @AfterAll
    static void cleanupSpec() {
        handler.getApplicationContext().close();
    }

    @Test
    void testHandler() {
        APIGatewayProxyRequestEvent request = new APIGatewayProxyRequestEvent();
        request.setPath("/");
        request.setHttpMethod(HttpMethod.GET.toString());
        var response = handler.handleRequest(request, new MockLambdaContext());

        assertEquals(HttpStatus.OK.getCode(), response.getStatusCode());
        assertEquals("{\"message\":\"Hello World\"}",  response.getBody());
    }
}

  • When you instantiate the Handler, the application context starts.

  • Remember to close your application context when you end your test. You can use your handler to obtain it.

  • You don’t invoke the controller directly. Instead, your handler receives an AWS Proxy Request event which it is routed transparently to your controller.

5. Testing the Application

To run the tests:

./mvnw test

6. Lambda

Create a Lambda Function. As a runtime, select Java 17.

create function

6.1. Upload Code

Create an executable jar including all dependencies:

./mvnw package

Upload it:

upload function code

6.2. Handler

As Handler, set:

io.micronaut.function.aws.proxy.payload1.ApiGatewayProxyRequestEventFunction

handler

6.3. Test

You can test it easily with a JSON Event:

{
  "path": "/",
  "httpMethod": "GET",
  "headers": {
    "Accept": "application/json"
  }
}

When working with Amazon API Gateway, it’s easy to use apigateway-aws-proxy as an Event Template to get started:

test event

You should see a 200 response:

test result

7. Next steps

Explore more features with Micronaut Guides.

Read more about:

8. Help with the Micronaut Framework

The Micronaut Foundation sponsored the creation of this Guide. A variety of consulting and support services are available.

9. License

All guides are released with an Apache license 2.0 license for the code and a Creative Commons Attribution 4.0 license for the writing and media (images…​).