Deploy a Micronaut application to AWS Lambda Java 11 Runtime

Learn how to distribute a Micronaut application to AWS Lambda 11 Runtime

Authors: Sergio del Amo

Micronaut Version: 2.5.0

1. Getting Started

In this guide we are going to create a Micronaut app written in Java.

2. What you will need

To complete this guide, you will need the following:

Some time on your hands
A decent text editor or IDE
JDK 1.8 or greater installed with JAVA_HOME configured appropriately

3. Solution

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

Download and unzip the source

4. Writing the App

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

mn create-app example.micronaut.micronautguide --feature=aws-lambda --build=gradle --lang=java

If you don’t specify the --build argument, Gradle is used as a build tool.
If you don’t specify the --lang argument, Java is used as a language.

If you use Micronaut Launch, add aws-lambda feature.

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

If you are using Java or Kotlin and IntelliJ IDEA, make sure you have enabled annotation processing.

The generated application contains a BookController. It responds to POST request to /.

src/main/java/example/micronaut/BookController.java

package example.micronaut;
import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Post;

import javax.validation.Valid;
import java.util.UUID;

@Controller
public class BookController {

    @Post
    public BookSaved save(@Valid @Body Book book) {
        BookSaved bookSaved = new BookSaved();
        bookSaved.setName(book.getName());
        bookSaved.setIsbn(UUID.randomUUID().toString());
        return bookSaved;
    }
}

The class is defined as a controller with the @Controller annotation mapped to the path /
The @Post annotation is used to map HTTP request to / to the the save method.
Add the @Valid annotation to any method parameter’s object which requires validation.

The controller’s method parameter is a Book object:

src/main/java/example/micronaut/Book.java

package example.micronaut;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.annotation.Introspected;
import javax.validation.constraints.NotBlank;

@Introspected
public class Book {

    @NonNull
    @NotBlank
    private String name;

    public Book() {
    }

    @NonNull
    public String getName() {
        return name;
    }

    public void setName(@NonNull String name) {
        this.name = name;
    }
}

Annotate the class with @Introspected to generate the Bean Metainformation at compile time.

It returns a BookSaved object:

src/main/java/example/micronaut/BookSaved.java

package example.micronaut;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.annotation.Introspected;

import javax.validation.constraints.NotBlank;

@Introspected
public class BookSaved {

    @NonNull
    @NotBlank
    private String name;

    @NonNull
    @NotBlank
    private String isbn;

    public BookSaved() {

    }

    @NonNull
    public String getName() {
        return name;
    }

    public void setName(@NonNull String name) {
        this.name = name;
    }

    @NonNull
    public String getIsbn() {
        return isbn;
    }

    public void setIsbn(@NonNull String isbn) {
        this.isbn = isbn;
    }
}

Annotate the class with @Introspected to generate the Bean Metainformation at compile time.

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

src/test/java/example/micronaut/BookControllerTest.java

package example.micronaut;
import com.amazonaws.serverless.exceptions.ContainerInitializationException;
import com.amazonaws.serverless.proxy.internal.testutils.AwsProxyRequestBuilder;
import com.amazonaws.serverless.proxy.internal.testutils.MockLambdaContext;
import com.amazonaws.serverless.proxy.model.AwsProxyRequest;
import com.amazonaws.serverless.proxy.model.AwsProxyResponse;
import com.amazonaws.services.lambda.runtime.Context;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import io.micronaut.http.HttpHeaders;
import io.micronaut.http.HttpMethod;
import io.micronaut.http.HttpStatus;
import io.micronaut.http.MediaType;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import io.micronaut.function.aws.proxy.MicronautLambdaHandler;

public class BookControllerTest {

    private static MicronautLambdaHandler handler;
    private static Context lambdaContext = new MockLambdaContext();
    private static ObjectMapper objectMapper;

    @BeforeAll
    public static void setupSpec() {
        try {
            handler = new MicronautLambdaHandler();
            objectMapper = handler.getApplicationContext().getBean(ObjectMapper.class);

        } catch (ContainerInitializationException e) {
            e.printStackTrace();
        }
    }

    @AfterAll
    public static void cleanupSpec() {
        handler.getApplicationContext().close();
    }

    @Test
    void testSaveBook() throws JsonProcessingException {
        Book book = new Book();
        book.setName("Building Microservices");
        String json = objectMapper.writeValueAsString(book);
        AwsProxyRequest request = new AwsProxyRequestBuilder("/", HttpMethod.POST.toString())
                .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON)
                .body(json)
                .build();
        AwsProxyResponse response = handler.handleRequest(request, lambdaContext);
        Assertions.assertEquals(HttpStatus.OK.getCode(), response.getStatusCode());
        BookSaved bookSaved = objectMapper.readValue(response.getBody(), BookSaved.class);
        Assertions.assertEquals(bookSaved.getName(), book.getName());
        Assertions.assertNotNull(bookSaved.getIsbn());
    }
}

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 a AWS Proxy Request event which it is routed transparently to your controller.

5. Testing the Application

To run the tests:

$ ./gradlew test
$ open build/reports/tests/test/index.html

6. Lambda

Create a Lambda Function. As a runtime, select Java 11 (Correto).

6.1. Upload Code

Create an executable jar including all dependencies:

$ ./gradlew assemble

Upload it:

6.2. Handler

As Handler, set:

io.micronaut.function.aws.proxy.MicronautLambdaHandler

6.3. Test

You can test it easily. As Event Template use apigateway-aws-proxy to get you started:

{
  "body": "{\"name\": \"Building Microservices\"}",
  "resource": "/",
  "path": "/",
  "httpMethod": "POST",
  "isBase64Encoded": false,
  "queryStringParameters": {},
  "multiValueQueryStringParameters": {},
  "pathParameters": {},
  "stageVariables": {},
  ...
}

You should see a 200 response:

7. Next steps

Explore more features with Micronaut Guides.

8. Help with Micronaut

Object Computing, Inc. (OCI) sponsored the creation of this Guide. A variety of consulting and support services are available.

Meet the Team.

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