Hibernate in Action

I have been trying to learn to use Hibernate over the last couple of days. After reading through the first 2 chapters in Hibernate In Action, I decided to try the "Message" example mentioned in the book. I used HSQLDB to persist the data. Initially I thought that we only needed to add the jdbc driver (i.e hsqldb.jar) and hibernate3.jar in the classpath. But then, a whole series of exceptions hit me in the face one after the other. Reading through the stack trace and resolving the exceptions one by one, I finally figured that the following jars need to be in the classpath for the program to run successfully.

• the jdbc driver (in my case hsqldb.jar)
• hibernate3.jar
• asm.jar
• cglib-2.1.jar
• commons-collections-2.1.1.jar
• commons-logging-1.0.4.jar
• log4j-1.2.9.jar
• jta.jar
• ehcache-1.1.jar
• dom4j-1.6.jar

All of these jars (except for the jdbc driver) come bundled with hibernate 3.0.

While specifying the configuration options for hibernate, we have 2 options --- either to use the hibernate.properties file or the hibernate.cfg.xml. There are subtle differences b/w these 2 methods :-

1) If you are using the hibernate.properties file --- While building the SessionFactory object, we don't need to call Configuration.configure() , but we do need to call Configuration.addResource() to specify the mapping files. i.e. --

Configuration configuration = new Configuration();
configuration.addResource("Messages/Message.hbm.xml");
SessionFactory sessionFactory = configuration.buildSessionFactory();

If you are using the C3P0 connection pool, you need to add c3p0-0.8.5.2.jar (comes with hibernate 3.0) to the classpath.

2) If you are using the hibernate.cfg.xml file --- While building the SessionFactory object, we do need to call Configuration.configure() , but we don't need to call Configuration.addResource() to specify the mapping files since we could specify it in hibernate.cfg.xml itself. i.e. --

Configuration configuration = new Configuration();
SessionFactory sessionFactory = configuration.configure().buildSessionFactory();

Hope this helps when you are writing your first hibernate program :-)