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: 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.

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 are going to deploy a Micronaut serverless function to AWS 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-serverless-function-aws-lambda.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-function-app example.micronaut.complete --features=aws-lambda

or use Micronaut Launch

2.1 Code

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 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.

The output is 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 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> { (1)

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

1	The class extends MicronautRequestHandler and defines input and output types.

The generated test shows how the 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(); (1)
    }

    @AfterAll
    public static void stopServer() {
        if (bookRequestHandler != null) {
            bookRequestHandler.getApplicationContext().close(); (2)
        }
    }

    @Test
    public void testHandler() {
        Book book = new Book();
        book.setName("Building Microservices");
        BookSaved bookSaved = bookRequestHandler.execute(book); (3)
        assertEquals(bookSaved.getName(),book.getName());
        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	Invoke the `execute` method of the handler.