This example shows use of @PersistenceContext to have an EntityManager with an EXTENDED persistence context injected into a @Stateful bean. A JPA @Entity bean is used with the EntityManager to create, persist and merge data to a database.

Creating the JPA Entity

The entity itself is simply a pojo annotated with @Entity. We create one called Movie which we can use to hold movie records.

package org.superbiz.injection.jpa;

import javax.persistence.Entity;

@Entity
public class Movie {

    @Id @GeneratedValue
    private long id;

    private String director;
    private String title;
    private int year;

    public Movie() {
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public Movie(String director, String title, int year) {
        this.director = director;
        this.title = title;
        this.year = year;
    }

    public String getDirector() {
        return director;
    }

    public void setDirector(String director) {
        this.director = director;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }
}

Configure the EntityManager via a persistence.xml file

The above Movie entity can be created, removed, updated or deleted via an EntityManager object. The EntityManager itself is configured via a META-INF/persistence.xml file that is placed in the same jar as the Movie entity.

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">

  <persistence-unit name="movie-unit">
    <jta-data-source>movieDatabase</jta-data-source>
    <non-jta-data-source>movieDatabaseUnmanaged</non-jta-data-source>
    <class>org.superbiz.injection.jpa.Movie</class>

    <properties>
      <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/>
    </properties>
  </persistence-unit>
</persistence>

Notice that the Movie entity is listed via a <class> element. This is not required, but can help when testing or when the Movie class is located in a different jar than the jar containing the persistence.xml file.

Injection via @PersistenceContext

The EntityManager itself is created by the container using the information in the persistence.xml, so to use it at runtime, we simply need to request it be injected into one of our components. We do this via @PersistenceContext

The @PersistenceContext annotation can be used on any CDI bean, EJB, Servlet, Servlet Listener, Servlet Filter, or JSF ManagedBean. If you don't use an EJB you will need to use a UserTransaction begin and commit transactions manually. A transaction is required for any of the create, update or delete methods of the EntityManager to work.

package org.superbiz.injection.jpa;

import javax.ejb.Stateful;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;
import javax.persistence.Query;
import java.util.List;

@Stateful
public class Movies {

    @PersistenceContext(unitName = "movie-unit", type = PersistenceContextType.EXTENDED)
    private EntityManager entityManager;

    public void addMovie(Movie movie) throws Exception {
        entityManager.persist(movie);
    }

    public void deleteMovie(Movie movie) throws Exception {
        entityManager.remove(movie);
    }

    public List<Movie> getMovies() throws Exception {
        Query query = entityManager.createQuery("SELECT m from Movie as m");
        return query.getResultList();
    }
}

This particular EntityManager is injected as an EXTENDED persistence context, which simply means that the EntityManager is created when the @Stateful bean is created and destroyed when the @Stateful bean is destroyed. Simply put, the data in the EntityManager is cached for the lifetime of the @Stateful bean.

The use of EXTENDED persistence contexts is only available to @Stateful beans. See the JPA Concepts page for an high level explanation of what a "persistence context" really is and how it is significant to JPA.

MoviesTest

Testing JPA is quite easy, we can simply use the EJBContainer API to create a container in our test case.

package org.superbiz.injection.jpa;

import junit.framework.TestCase;

import javax.ejb.embeddable.EJBContainer;
import javax.naming.Context;
import java.util.List;
import java.util.Properties;

//START SNIPPET: code
public class MoviesTest extends TestCase {

    public void test() throws Exception {

        final Properties p = new Properties();
        p.put("movieDatabase", "new://Resource?type=DataSource");
        p.put("movieDatabase.JdbcDriver", "org.hsqldb.jdbcDriver");
        p.put("movieDatabase.JdbcUrl", "jdbc:hsqldb:mem:moviedb");

        final Context context = EJBContainer.createEJBContainer(p).getContext();

        Movies movies = (Movies) context.lookup("java:global/injection-of-entitymanager/Movies");

        movies.addMovie(new Movie("Quentin Tarantino", "Reservoir Dogs", 1992));
        movies.addMovie(new Movie("Joel Coen", "Fargo", 1996));
        movies.addMovie(new Movie("Joel Coen", "The Big Lebowski", 1998));

        List<Movie> list = movies.getMovies();
        assertEquals("List.size()", 3, list.size());

        for (Movie movie : list) {
            movies.deleteMovie(movie);
        }

        assertEquals("Movies.getMovies()", 0, movies.getMovies().size());
    }
}

Running

When we run our test case we should see output similar to the following.

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.superbiz.injection.jpa.MoviesTest
Apache OpenEJB 4.0.0-beta-1    build: 20111002-04:06
http://openejb.apache.org/
INFO - openejb.home = /Users/dblevins/examples/injection-of-entitymanager
INFO - openejb.base = /Users/dblevins/examples/injection-of-entitymanager
INFO - Using 'javax.ejb.embeddable.EJBContainer=true'
INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service)
INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager)
INFO - Configuring Service(id=movieDatabase, type=Resource, provider-id=Default JDBC Database)
INFO - Found EjbModule in classpath: /Users/dblevins/examples/injection-of-entitymanager/target/classes
INFO - Beginning load: /Users/dblevins/examples/injection-of-entitymanager/target/classes
INFO - Configuring enterprise application: /Users/dblevins/examples/injection-of-entitymanager
INFO - Configuring Service(id=Default Stateful Container, type=Container, provider-id=Default Stateful Container)
INFO - Auto-creating a container for bean Movies: Container(type=STATEFUL, id=Default Stateful Container)
INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container)
INFO - Auto-creating a container for bean org.superbiz.injection.jpa.MoviesTest: Container(type=MANAGED, id=Default Managed Container)
INFO - Configuring PersistenceUnit(name=movie-unit)
INFO - Auto-creating a Resource with id 'movieDatabaseNonJta' of type 'DataSource for 'movie-unit'.
INFO - Configuring Service(id=movieDatabaseNonJta, type=Resource, provider-id=movieDatabase)
INFO - Adjusting PersistenceUnit movie-unit <non-jta-data-source> to Resource ID 'movieDatabaseNonJta' from 'movieDatabaseUnmanaged'
INFO - Enterprise application "/Users/dblevins/examples/injection-of-entitymanager" loaded.
INFO - Assembling app: /Users/dblevins/examples/injection-of-entitymanager
INFO - PersistenceUnit(name=movie-unit, provider=org.apache.openjpa.persistence.PersistenceProviderImpl) - provider time 462ms
INFO - Jndi(name="java:global/injection-of-entitymanager/Movies!org.superbiz.injection.jpa.Movies")
INFO - Jndi(name="java:global/injection-of-entitymanager/Movies")
INFO - Jndi(name="java:global/EjbModule1461341140/org.superbiz.injection.jpa.MoviesTest!org.superbiz.injection.jpa.MoviesTest")
INFO - Jndi(name="java:global/EjbModule1461341140/org.superbiz.injection.jpa.MoviesTest")
INFO - Created Ejb(deployment-id=Movies, ejb-name=Movies, container=Default Stateful Container)
INFO - Created Ejb(deployment-id=org.superbiz.injection.jpa.MoviesTest, ejb-name=org.superbiz.injection.jpa.MoviesTest, container=Default Managed Container)
INFO - Started Ejb(deployment-id=Movies, ejb-name=Movies, container=Default Stateful Container)
INFO - Started Ejb(deployment-id=org.superbiz.injection.jpa.MoviesTest, ejb-name=org.superbiz.injection.jpa.MoviesTest, container=Default Managed Container)
INFO - Deployed Application(path=/Users/dblevins/examples/injection-of-entitymanager)
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.301 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

APIs Used

Source

svn co http://svn.apache.org/repos/asf/tomee/tomee/trunk/examples/injection-of-entitymanager
cd injection-of-entitymanager
mvn clean install