Deploy a Serverless Micronaut function to AWS Lambda Java 11 Runtime

Learn how to distribute a serverless Micronaut function to AWS Lambda 11 Runtime

Authors: Sergio del Amo

Micronaut Version: 3.1.0

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.

If you want to respond to triggers such as queue events, S3 events, or single endpoints, you should opt to code your Micronaut functions as Serverless functions.

In this guide, we will deploy a Micronaut serverless function to AWS Lambda.

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:

  • 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 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-function-app example.micronaut.micronautguide --features=aws-lambda --build=gradle --lang=java
If you don’t specify the --build argument, Gradle is used as the build tool.
If you don’t specify the --lang argument, Java is used as the language.

If you use Micronaut Launch, select serverless function as application type and add the aws-lambda feature.

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

4.1. Enable annotation Processing

If you use Java or Kotlin and IntelliJ IDEA, make sure to enable annotation processing.

annotationprocessorsintellij

We want to support a JavaBean as input and output types.

The input 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.

The output is 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 application contains a class extending MicronautRequestHandler

src/main/java/example/micronaut/BookRequestHandler.java
package example.micronaut;
import io.micronaut.core.annotation.Introspected;
import io.micronaut.function.aws.MicronautRequestHandler;
import java.util.UUID;

@Introspected
public class BookRequestHandler extends MicronautRequestHandler<Book, BookSaved> {

    @Override
    public BookSaved execute(Book input) {
        BookSaved bookSaved = new BookSaved();
        bookSaved.setName(input.getName());
        bookSaved.setIsbn(UUID.randomUUID().toString());
        return bookSaved;
    }
}

The generated test shows how to verify the function behaviour:

src/test/java/example/micronaut/BookRequestHandlerTest.java
package example.micronaut;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

public class BookRequestHandlerTest {

    private static BookRequestHandler bookRequestHandler;

    @BeforeAll
    public static void setupServer() {
        bookRequestHandler = new BookRequestHandler();
    }

    @AfterAll
    public static void stopServer() {
        if (bookRequestHandler != null) {
            bookRequestHandler.getApplicationContext().close();
        }
    }

    @Test
    public void testHandler() {
        Book book = new Book();
        book.setName("Building Microservices");
        BookSaved bookSaved = bookRequestHandler.execute(book);
        assertEquals(bookSaved.getName(),book.getName());
        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.

  • Invoke the execute method of the handler.

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).

create function

6.1. Upload Code

Create an executable jar including all dependencies:

$ ./gradlew assemble

Upload it:

upload function code

6.2. Handler

As Handler, set:

example.micronaut.BookRequestHandler

handler 2

6.3. Test

You can test it easily.

test event 2
{
  "name": "Building Microservices"
}

You should see a 200 response:

test result 2

7. Next steps

Explore more features with Micronaut Guides.

Read more about:

8. Help with the Micronaut Framework

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