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Serverless TomEE Plus

Apache TomEE can be run as a library inside your JVM with no need for separate processes or a standalone server install. In this approach we include the right libraries in our project and then bootstrap TomEE using the Server.Builder API.

Include the tomee-plus dependency

To make things as easy as possible there is just one dependency that will give you a classpath that is 100% identical to your favorite Apache TomEE distribution. The following dependency will pull give you an environment identical to an Apache TomEE Plus binary distribution.

<dependency>
  <groupId>org.apache.tomee.bom</groupId>
  <artifactId>tomee-plus</artifactId>
  <version>${version.tomee}</version>
</dependency>
The org.apache.tomee.bom:tomee-plus is actually generated by analyzing the apache-tomee-plus-x.y.z.zip, so is guaranteed to be 100% identical making it easy to transition from a zip file to a simple maven dependency.

Write Regular Code

Here we see a simple JAX-RS API for sending/recieving Movie objects as JSON.

@Path("/movies")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
@RequestScoped
public class MovieService {

    private Map<Integer, Movie> store = new ConcurrentHashMap<>();

    @PostConstruct
    public void construct(){
        this.addMovie(new Movie("Wedding Crashers", "David Dobkin", "Comedy", 1, 2005));
        this.addMovie(new Movie("Starsky & Hutch", "Todd Phillips", "Action", 2, 2004));
        this.addMovie(new Movie("Shanghai Knights", "David Dobkin", "Action", 3, 2003));
        this.addMovie(new Movie("I-Spy", "Betty Thomas", "Adventure", 4, 2002));
        this.addMovie(new Movie("The Royal Tenenbaums", "Wes Anderson", "Comedy", 5, 2001));
        this.addMovie(new Movie("Zoolander", "Ben Stiller", "Comedy", 6, 2001));
    }
    @GET
    public List<Movie> getAllMovies() {
        return new ArrayList<>(store.values());
    }

    @POST
    public Movie addMovie(final Movie newMovie) {
        store.put(newMovie.getId(), newMovie);
        return newMovie;
    }

}

Bootstrap TomEE with the Server Builder

A this point we have a Maven project with the right dependencies and some application code in our project. From here we use the Server.Builder API to construct a Server instance inside our JVM.

Here we see a simple Main class that bootstraps a Server instance on port 8080 and blocks:

import org.apache.tomee.bootstrap.Archive;
import org.apache.tomee.bootstrap.Server;

import java.util.concurrent.Semaphore;

public class Main {
    public static void main(String[] args) throws InterruptedException {

        final Server server = Server.builder()
                .httpPort(8080)
                .add("webapps/ROOT/WEB-INF/classes", Archive.archive()
                        .add(Api.class)
                        .add(Movie.class)
                        .add(MovieService.class))
                .build();

        System.out.println("Listening for requests at " + server.getURI());
        new Semaphore(0).acquire();
    }
}

The example below bootstraps a Server instance on random ports inside a test case and exits when the test case is complete:

import org.apache.tomee.bootstrap.Archive;
import org.apache.tomee.bootstrap.Server;
//...

public class MovieServiceTest {

    private static URI serverURI;

    @BeforeClass
    public static void setup() {
        // Add any classes you need to an Archive
        // or add them to a jar via any means
        final Archive classes = Archive.archive()
                .add(Api.class)
                .add(Movie.class)
                .add(MovieService.class);

        // Place the classes where you would want
        // them in a Tomcat install
        final Server server = Server.builder()
                // This effectively creates a webapp called ROOT
                .add("webapps/ROOT/WEB-INF/classes", classes)
                .build();

        serverURI = server.getURI();
    }

    @Test
    public void getAllMovies() {
        final WebTarget target = ClientBuilder.newClient().target(serverURI);

        final Movie[] movies = target.path("/api/movies").request().get(Movie[].class);

        assertEquals(6, movies.length);

        final Movie movie = movies[1];
        assertEquals("Todd Phillips", movie.getDirector());
        assertEquals("Starsky & Hutch", movie.getTitle());
        assertEquals("Action", movie.getGenre());
        assertEquals(2004, movie.getYear());
        assertEquals(2, movie.getId());
    }
}

In the above code we have assembled the classes Api, Movie and MovieService into a virtual archive, then we add that archive into a virtual Tomcat install at the location webapps/ROOT/WEB-INF/classes. When we call build() the Tomcat server instance is started in our JVM and will begin serving HTTP requests at the host/port identified by server.getURI()

In short, we’ve bootstrapped a Tomcat server in our JVM that has a very tiny disk footprint; three classes and a handful of default configuration files.

Running

Were we to run the above Main class or Test Case we’d see output like the following:

Sep 03, 2020 8:41:29 AM org.apache.openejb.server.cxf.rs.CxfRsHttpListener deployApplication
INFO:      org.apache.cxf.jaxrs.validation.ValidationExceptionMapper@2d313c8c
Sep 03, 2020 8:41:29 AM org.apache.openejb.server.cxf.rs.CxfRsHttpListener logEndpoints
INFO: REST Application: http://localhost:8080/api        -> org.superbiz.movie.Api@6b2dd3df
Sep 03, 2020 8:41:29 AM org.apache.openejb.server.cxf.rs.CxfRsHttpListener logEndpoints
INFO:      Service URI: http://localhost:8080/api/movies -> Pojo org.superbiz.movie.MovieService
Sep 03, 2020 8:41:29 AM org.apache.openejb.server.cxf.rs.CxfRsHttpListener logEndpoints
INFO:               GET http://localhost:8080/api/movies ->      List<Movie> getAllMovies()
Sep 03, 2020 8:41:29 AM org.apache.openejb.server.cxf.rs.CxfRsHttpListener logEndpoints
INFO:              POST http://localhost:8080/api/movies ->      Movie addMovie(Movie)
Sep 03, 2020 8:41:29 AM jdk.internal.reflect.DelegatingMethodAccessorImpl invoke
INFO: Deployment of web application directory [/private/var/folders/bd/f9ntqy1m8xj_fs006s6crtjh0000gn/T/temp14966428831095231081dir/apache-tomee/webapps/ROOT] has finished in [1,798] ms
Sep 03, 2020 8:41:29 AM jdk.internal.reflect.DelegatingMethodAccessorImpl invoke
INFO: Starting ProtocolHandler ["http-nio-8080"]
Sep 03, 2020 8:41:29 AM jdk.internal.reflect.DelegatingMethodAccessorImpl invoke
INFO: Server startup in [1877] milliseconds
Sep 03, 2020 8:41:29 AM jdk.internal.reflect.DelegatingMethodAccessorImpl invoke
INFO: Full bootstrap in [3545] milliseconds
Listening for requests at http://localhost:8080

APIs Used