GWT and JRE managed persistence (JPA) with Apache Derby

A while back I was playing with JPA/EJB3 persistence and GWT (Google Web Toolkit) but didn't want to use a heavy weight Application Server . The idea behind the application I was looking at was that it should be distributable and always run locally.

I downloaded the hibernate and JPA annotations from the hibernate website and thought it would be a simple case of configuring the persistence.xml file. After a some difficulties getting my application to hit the test Derby database I turned to google and it seems others had problems too.

I was expecting to have to create the persistence.xml file under “war/META-INF/” in my eclipse project. This is just wrong, it seems the persistence.xml file has to be on the classpath when your not using container based persistence.

The next problem I encountered was that I'd not included all the necessary jars from the hibernate distribution. The following combination seemed to work for me in the end.

WEB-INF/lib/

• hibernate3.jar
• hibernate-jpa-2.0-api.1.0.0.Final.jar
• javassist-3.12.0.GA.jar
• jta-1.1.jar
• slf3j-api-1.6.1.jar

My persistence.xml was as follows:

<persistence 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 persistence_1_0.xsd" version="1.0">
  <persistence-unit name="default" transaction-type="RESOURCE_LOCAL">
   <provider>org.hibernate.ejb.HibernatePersistence</provider>  
  <properties>  
   <property name="hibernate.archive.autodetection" value="class" />  
   <property name="hibernate.format_sql" value="true" />  
   <property name="hibernate.show_sql" value="true" />  
   <!-- <property name="hibernate.hbm2ddl.auto" value="create-drop" />-->  
   <property name="hibernate.connection.url" value="jdbc:derby://localhost:1527/slicr;" />  
   <property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.ClientDriver" />  
   <property name="hibernate.dialect" value="org.hibernate.dialect.DerbyDialect" />  
   <!-- <property name="hibernate.connection.username" value="user" />  
   <property name="hibernate.connection.password" value="password" /> -->  
  </properties>    
  </persistence-unit>
</persistence>

I was only knocking up a quick and dirty application as a learning exercise but spent a good couple of hours just trying to hit the database. Hopefully this will help others in the same situation.