index-group=Unrevised type=page status=published title=Injection Of Entitymanager

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](../../jpa-concepts.html) 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://tomee.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