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 Kotlin.

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=maven --lang=kotlin
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/kotlin/example/micronaut/Book.kt
package example.micronaut
import io.micronaut.core.annotation.Introspected

@Introspected
class Book {
    var name: String? = null
}
  • Annotate the class with @Introspected to generate the Bean Metainformation at compile time.

The output is a BookSaved object:

src/main/kotlin/example/micronaut/BookSaved.kt
package example.micronaut
import io.micronaut.core.annotation.Introspected

@Introspected
class BookSaved {
    var name: String? = null
    var isbn: String? = null
}
  • Annotate the class with @Introspected to generate the Bean Metainformation at compile time.

The application contains a class extending MicronautRequestHandler

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

@Introspected
class BookRequestHandler : MicronautRequestHandler<Book?, BookSaved?>() {

    override fun execute(input: Book?): BookSaved? {
        return if (input != null) {
            val bookSaved = BookSaved()
            bookSaved.name = input.name
            bookSaved.isbn = UUID.randomUUID().toString()
            return bookSaved
        } else {
            null
        }
    }
}

The generated test shows how to verify the function behaviour:

src/test/kotlin/example/micronaut/BookRequestHandlerTest.kt
package example.micronaut
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.Assertions

class BookRequestHandlerTest {

    @Test
    fun testHandler() {
        val bookRequestHandler = BookRequestHandler()
        val book = Book()
        book.name = "Building Microservices"
        val bookSaved = bookRequestHandler.execute(book)
        Assertions.assertNotNull(bookSaved)
        Assertions.assertEquals(book.name, bookSaved!!.name)
        Assertions.assertNotNull(bookSaved.isbn)
        bookRequestHandler.applicationContext.close()
    }
}
  • 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:

$ ./mvnw test

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:

$ ./mvnw package

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.