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: 3.2.7

1. Getting Started

In this guide, we will create a Micronaut application written in Groovy.

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-app example.micronaut.micronautguide --features=aws-lambda --build=gradle --lang=groovy
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, add the aws-lambda feature.

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

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

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 groovy.transform.CompileStatic

class BookController {

    BookSaved save(@Valid @Body Book book) {
        BookSaved bookSaved = new BookSaved() =
        bookSaved.isbn = UUID.randomUUID().toString()
  • The class is defined as a controller with the @Controller annotation mapped to the path /

  • The @Post annotation maps HTTP requests to / to the save method.

  • Add the @Valid annotation to any method parameter which requires validation.

The controller method parameter is a Book object:

package example.micronaut
import io.micronaut.core.annotation.NonNull
import io.micronaut.core.annotation.Introspected
import javax.validation.constraints.NotBlank
import groovy.transform.CompileStatic

class Book {

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

It returns a BookSaved object:

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

class BookSaved {

    String name

    String 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:

package example.micronaut
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.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 spock.lang.Specification
import spock.lang.Shared
import spock.lang.AutoCleanup

class BookControllerSpec extends Specification {

    MicronautLambdaHandler handler = new MicronautLambdaHandler()

    Context lambdaContext = new MockLambdaContext()

    ObjectMapper objectMapper = handler.applicationContext.getBean(ObjectMapper)

    void "test save Book"() {
        Book book = new Book() = "Building Microservices"
        String json = objectMapper.writeValueAsString(book)

        AwsProxyRequest request = new AwsProxyRequestBuilder("/", HttpMethod.POST.toString())
                .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON)
        AwsProxyResponse response = handler.handleRequest(request, lambdaContext)

        HttpStatus.OK.code == response.statusCode

        BookSaved bookSaved = objectMapper.readValue(response.body, BookSaved)

        then: ==
  • 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 an AWS Proxy Request event which it is routed transparently to your controller.

5. Testing the Application

To run the tests:

./gradlew test

Then open build/reports/tests/test/index.html in a browser to see the results.

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:


6.3. Test

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

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

You should see a 200 response:

test result

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.