This example shows the persist, remove and creation a query in JPA Hibernate. The Java Persistence API (JPA) is a Java specification for accessing, persisting, and managing data between Java objects / classes and a relational database.

To exemplify the use of JPA, we will persist an Object (Movie) in the database.

Links to the documentation have been added in key parts of the example for the case of doubts and as a way to encourage their reading for details.

Movie

Here we have a class with some details. See the annotation @Entity above the declaration, with it we are saying that this class is an entity (a table in the database). We still have two more annotations above the attribute id, one of them is @Id annotation, it indicates that this attribute is the identifier of the entity and the other annotation @GeneratedValue indicates that the unique identifier value generation of the entity will be managed by the persistence provider.

package org.superbiz.injection.h3jpa;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Movie {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

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

    public Movie() {
    }

    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;
    }

}

Movies

Now we have two important things: @PersistenceContext annotation and the EntityManager declaration. The EntityManager is the interface with the core methods of JPA like persist, remove, merge, find and others… We annotate the EntityManager with @PersistenceContext, a persistence context is an entity management where every persistence context associated with a persistence unit, we will create a persistence.xml soon for this.

package org.superbiz.injection.h3jpa;

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();
    }
}

persistence.xml

Here we define which database will persist our movies, and we perform other configurations such as: define a persistence-unit with the name movie-unit, followed by the definition of the JPA provider/implementation (in this case Hibernate) and we set some properties for hibernate:

<persistence version="1.0"
             xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="movie-unit">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <jta-data-source>movieDatabase</jta-data-source>
    <non-jta-data-source>movieDatabaseUnmanaged</non-jta-data-source>
    <properties>
      <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
    </properties>
  </persistence-unit>
</persistence>

MoviesTest

Now we do a test, persisting three films, then we perform a search and finally we delete them.

package org.superbiz.injection.h3jpa;

import junit.framework.TestCase;

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

/**
 * @version $Revision: 607077 $ $Date: 2007-12-27 06:55:23 -0800 (Thu, 27 Dec 2007) $
 */
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/jpa-hibernate/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

To run the example via maven:

Access the project folder:

cd jpa-hibernate

And execute:

mvn clean install

Which will generate output similar to the following:

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.superbiz.injection.h3jpa.MoviesTest
Apache OpenEJB 4.0.0-beta-1    build: 20111002-04:06
http://tomee.apache.org/
INFO - openejb.home = /Users/dblevins/examples/jpa-hibernate
INFO - openejb.base = /Users/dblevins/examples/jpa-hibernate
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/jpa-hibernate/target/classes
INFO - Beginning load: /Users/dblevins/examples/jpa-hibernate/target/classes
INFO - Configuring enterprise application: /Users/dblevins/examples/jpa-hibernate
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.h3jpa.MoviesTest: Container(type=MANAGED, id=Default Managed Container)
INFO - Configuring PersistenceUnit(name=movie-unit, provider=org.hibernate.ejb.HibernatePersistence)
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/jpa-hibernate" loaded.
INFO - Assembling app: /Users/dblevins/examples/jpa-hibernate
INFO - PersistenceUnit(name=movie-unit, provider=org.hibernate.ejb.HibernatePersistence) - provider time 631ms
INFO - Jndi(name="java:global/jpa-hibernate/Movies!org.superbiz.injection.h3jpa.Movies")
INFO - Jndi(name="java:global/jpa-hibernate/Movies")
INFO - Jndi(name="java:global/EjbModule1235930463/org.superbiz.injection.h3jpa.MoviesTest!org.superbiz.injection.h3jpa.MoviesTest")
INFO - Jndi(name="java:global/EjbModule1235930463/org.superbiz.injection.h3jpa.MoviesTest")
INFO - Created Ejb(deployment-id=Movies, ejb-name=Movies, container=Default Stateful Container)
INFO - Created Ejb(deployment-id=org.superbiz.injection.h3jpa.MoviesTest, ejb-name=org.superbiz.injection.h3jpa.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.h3jpa.MoviesTest, ejb-name=org.superbiz.injection.h3jpa.MoviesTest, container=Default Managed Container)
INFO - Deployed Application(path=/Users/dblevins/examples/jpa-hibernate)
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.22 sec

Results :

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