While preparing for a workshop on the EJB 3.0 Persistence API that I will present later today, I decided – against all the instructions in demo-school and presentation-college – to make a last minute change: replace the Glassfish libraries from build 20 (december 2005) with the new Glassfish stand-alone Persistence implementation (see: https://glassfish.dev.java.net/downloads/persistence/JavaPersistence.html) (that is 2 Mb instead of 80 or so). What I did not count on, is that since the build I used before, there have been several changes in the Annotations used for defining the Object Relational Mapping. As a result, my demos did not function anymore, and some of the labs were rendered incorrect.

 

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Using the most recent EJB 3.0 Persistence Specification document I tried to correct, one by one, the errors my compilation as well as runtime execution ran into. Here a summary of the changes I had to make:

@ID – no longer has any attributes. No more generate and generator attributes

@GeneratedValue – the following method is now used for specifying the fact that the value for an attribute during insert into the database should be retrieved from a database sequence:

    @Id    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="ALS_PBR_SEQ")    @Column    public Long getId() {        return id;    }

We also need to import two classes:

import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;

@NamedQuery – the attribute queryString is now simply called query.

@JoinTable – the attribute table (of type @Table) is dropped. Now we simply use name to specify the name of the JoinTable. For example:

@ManyToMany(cascade=CascadeType.ALL)    @JoinTable(name = "als_authorships", joinColumns = {           @JoinColumn(name = "atr_id")       }, inverseJoinColumns = {           @JoinColumn(name = "bok_id")       })

Then the persistence.xml underwent some changes:

We need to add the attribute version="1.0" to the persistence element:

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0"> 

And the property-names were changed; instead of just jdbc.driver, jdbc.url etc., the standalone Glassfish Persistence implementation requires the property names to be prefixed with toplink.jdbc…. It does not seem likely that this change is a JSR-220 modification, it is more likely that this reflects an internal change in the Glassfish code.

<properties>  <property name="toplink.jdbc.driver" value="<database driver>"/>  <property name="toplink.jdbc.url" value="<database url>"/>  <property name="toplink.jdbc.user" value="<user>"/>  <property name="toplink.jdbc.password" value="<password>"/>  <property name="toplink.logging.level" value="INFO"/></properties>

 

Since most of these changes seem improvements, I am not hugely disappointed. And I found about these just in time for my workshop.

 

Resources

 

http://trycatchfinally.blogspot.com/2006/01/experiments-with-ejb-30-id-annotation.html on how to get started with Glassfish Stand Alone persistence 

Java Community Process on EJB 3.0 Persistence 

Glassfish Reference Implementation of EJB 3.0 Persistence