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: 2.0.1

1 Getting Started

Please, read about Micronaut AWS Lambda Support to learn more about different Lambda runtime, Triggers and Handlers and how to integrate with a Micronaut application.

In this guide, we are going to deploy a Micronaut Application to AWS Lambda. If your Lambda integrates with API Gateway via a Lambda Proxy, a Micronaut function of type Application with the aws-lambda feature is a good fit. Specially, when you have multiple endpoints which you wish to delegate to a single Lambda.

1.1 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

You will need also an AWS Account.

1.2 Solution

We recommend you to 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

Clone the Git repository: git clone https://github.com/micronaut-guides/mn-application-aws-lambda-java11.git

Then, cd into the complete folder which you will find in the root project of the downloaded/cloned project.

2 Writing the App

Create a micronaut application with the aws-lambda feature using the CLI:

% mn create-app example.micronaut.complete --features=aws-lambda

or use Micronaut Launch

2.1 Code

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 (1)
public class BookController {

    @Post (2)
    public BookSaved save(@Valid @Body Book book) { (3)
        BookSaved bookSaved = new BookSaved();
        bookSaved.setName(book.getName());
        bookSaved.setIsbn(UUID.randomUUID().toString());
        return bookSaved;
    }
}

1	The class is defined as a controller with the `@Controller` annotation mapped to the path /
2	The `@Post` annotation is used to map HTTP request to `/` to the the `save` method.
3	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 edu.umd.cs.findbugs.annotations.NonNull;
import io.micronaut.core.annotation.Introspected;
import javax.validation.constraints.NotBlank;

@Introspected (1)
public class Book {

    @NotBlank (2)
    @NonNull (3)
    private String name;

    public Book() {
    }

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

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

1	Annotate the class with `@Introspected` to generate the Bean Metainformation at compile time.
2	`name` is required
3	Add a nullability annotation to help with Kotlin interoperability and help the IDE.

It returns a BookSaved object:

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

package example.micronaut;
import edu.umd.cs.findbugs.annotations.NonNull;
import io.micronaut.core.annotation.Introspected;

import javax.validation.constraints.NotBlank;

@Introspected (1)
public class BookSaved {

    @NotBlank (2)
    @NonNull (3)
    private String name;

    @NotBlank (2)
    @NonNull (3)
    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;
    }
}

1	Annotate the class with `@Introspected` to generate the Bean Metainformation at compile time.
2	`name` and `isbn` are required
3	Add a nullability annotation to help with Kotlin interoperability and help the IDE.

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(); (1)
            objectMapper = handler.getApplicationContext().getBean(ObjectMapper.class);

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

    @AfterAll
    public static void cleanupSpec() {
        handler.getApplicationContext().close(); (2)
    }

    @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); (3)
        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());
    }
}

1	When you instantiate the Handler, the application context starts.
2	Remember to close your application context when you end your test. You can use your handler to obtain it.
3	You don’t invoke the controller directly. Instead, your handler receives a AWS Proxy Request event which it is routed transparently to your controller.