Simple Hibernate POJO example

[Christopher Rygaard]

Simple POJO Example

This is the simplest stand-alone Hibernate example I could cook up.

Notice: This is provided with no warranty whatsoever. Use at your own risk.

This is the POJO class:

@javax.persistence.Entity
public class MyPersistentObject
{
   @javax.persistence.Id
   @javax.persistence.GeneratedValue( generator = "increment" )
   @org.hibernate.annotations.GenericGenerator( name = "increment", strategy = "increment" )
   private Long           _persistenceID;

   private String         _title;

   @javax.persistence.Temporal( javax.persistence.TemporalType.TIMESTAMP )
   @javax.persistence.Column( name = "OBJECT_DATE" )
   private java.util.Date _date;

   // Hibernate needs a no-argument constructor
   private MyPersistentObject()
   {
   }

   // for application use, to create new persistent objects
   public MyPersistentObject( String         title,
                              java.util.Date date )
   {
      _title = title;
      _date = date;
   }

   public java.util.Date getDate()
   {
      return _date;
   }

   public String getTitle()
   {
      return _title;
   }
}

And here is a simple example of how to use the POJO class:

public class HibernateExample
{
   private org.hibernate.SessionFactory _sessionFactory;
   private MyPersistentObject           _myPersistentObject1;
   private MyPersistentObject           _myPersistentObject2;
   private MyPersistentObject           _myPersistentObject3;

   final static public void main( String arguments[] )
   {
      HibernateExample example;
      example = new HibernateExample();
      example.createPersistentObjects();
      example.readAndDisplayPersistentObjects();
      example.manipulatePersistentObjects();
      example.readAndDisplayPersistentObjects();
      example.cleanup();
   }

   private HibernateExample()
   {
      org.hibernate.cfg.Configuration configuration;

      java.util.logging.Logger.getLogger( "org.hibernate" ).setLevel( java.util.logging.Level.SEVERE );  // Supress Hibernate's excessive output

      configuration = new org.hibernate.cfg.Configuration();
      configuration.setProperty( "hibernate.dialect",                 "org.hibernate.dialect.H2Dialect" );                                          // Customize this for your particular RDBMS
      configuration.setProperty( "hibernate.connection.driver_class", "org.h2.Driver" );                                                            // Customize this for your particular RDBMS
      configuration.setProperty( "hibernate.connection.url",          "jdbc:h2:file:C:/SFTData/SFTDatabases/SFTInterfaceData;DB_CLOSE_DELAY=-1" );  // Customize this for your particular RDBMS
      configuration.setProperty( "hibernate.connection.username",     "sa" );                                                                       // Customize this for your particular RDBMS
      configuration.setProperty( "hibernate.connection.password",     "" );                                 // Customize this for your particular RDBMS installation
      configuration.setProperty( "hibernate.connection.pool_size",    "1" );                                // Customize this for your particular RDBMS installation
      configuration.setProperty( "hibernate.cache.provider_class",    "org.hibernate.cache.internal.NoCacheProvider" );  // This is not ready for prime-time
      configuration.setProperty( "hibernate.show_sql",                "false" );  // Tell hibernate to not echo the SQL
      configuration.setProperty( "hibernate.hbm2ddl.auto",            "create" );
      configuration.addAnnotatedClass( MyPersistentObject.class );

      _sessionFactory = configuration.buildSessionFactory();
   }

   final private void createPersistentObjects()
   {
      org.hibernate.Session     session;
      boolean                   committed;
      org.hibernate.Transaction transaction;

      session = _sessionFactory.openSession();

      try
      {
         committed = false;
         transaction = session.beginTransaction();

         try
         {
            _myPersistentObject1 = new MyPersistentObject( "First persistent object", new java.util.Date() );
            session.save( _myPersistentObject1 );

            _myPersistentObject2 = new MyPersistentObject( "A second persistent object", new java.util.Date() );
            session.save( _myPersistentObject2 );

            transaction.commit();
            committed = true;
         }
         finally
         {
            if ( !committed )
            {
               transaction.rollback();
            }
         }
      }
      finally
      {
         session.close();
      }
   }

   final private void manipulatePersistentObjects()
   {
      org.hibernate.Session     session;
      org.hibernate.Transaction transaction;

      session = _sessionFactory.openSession();

      try
      {
         transaction = session.beginTransaction();

         _myPersistentObject3 = new MyPersistentObject( "A third persistent object", new java.util.Date() );
         session.save( _myPersistentObject3 );

         session.delete( _myPersistentObject2 );

         transaction.commit();
      }
      finally
      {
         session.close();
      }
   }

   final private void readAndDisplayPersistentObjects()
   {
      org.hibernate.Session session;
      java.util.List<MyPersistentObject> result;

      session = _sessionFactory.openSession();

      try
      {
         session.beginTransaction();

         result = (java.util.List<MyPersistentObject>)( session.createQuery("from MyPersistentObject").list() );

         for ( MyPersistentObject persistentObject: result )
         {
            System.out.println( "MyPersistentObject (" + persistentObject.getDate() + ") : " + persistentObject.getTitle() );
         }

         session.getTransaction().commit();
      }
      finally
      {
         session.close();
      }
   }

   final private void cleanup()
   {
      if ( _sessionFactory != null )
      {
         _sessionFactory.close();
      }
   }
}