Monday, September 03, 2007

EJB 3.0 with JBoss 4.2.1 GA and Netbeans IDE 5.5.1

I have started to read O'reilly's EJB 3.0 5th Edition by Bill Burke and Richard Monson-Haefel. The book covers EJB 3.0 and Java Persistence 1.0 in detail. It comes with a JBoss workbook for JBoss 4.0.3 release. I installed the current stable release JBoss 4.2.1 GA for my practice. Unlike the 4.0.x releases, the JBoss 4.2.x release has the EJB 3 enabled by default. I used Netbeans 5.5.1 IDE for development. It supports JBoss 4.x and even 5.x (which is still in beta). It readily recognized my JBoss 4.2.1 installation in the server manager. I created a project as Enterprise Application (with both web and ejb modules). The persistence configuration was simple and i used the default datasource HSQL DB 1.8.

There were some gotchas before i could get chapter 4 "Developing your first bean" examples working:
1. one has to change this "DefaultDS" to "java:/DefaultDS" in the META-INF/persistence.xml of your ejb module.
2. also, in the client application, you will need to reference the "TravelAgentBean/remote" as "<Your EAR application name>/TravelAgentBean/remote". To be sure as to where in the jndi tree has your session bean got registered, you can browse to jmx-console (http://localhost:8080/jmx-console) and look for "service=JNDIView". Click on the link and in the following page, invoke the method list() to see the list of names in the JNDI tree. From there you can know for sure what name to use for lookup at client end for your session facade.
3. lastly, i had mistakenly had my entity bean's id annotated as @GeneratedValue in which case when i used to call the setId() method in my session facade bean, then it used to throw an exception while persisting using EntityManager's persist() that the entity instance is detached one. So, i could either remove the annotation of generated value or don't set the id.
4. at client end, there is no need for PortableRemoteObject.narrow() method anymore. You can simply use Java casting.

For my simple example, i did not have to pass the JNDI bootstrap params as properties instance to InitialContext() constructor.

Eclipse 3.3 (Europa) has a very nice OR mapping tool called Dali, but i am yet to figure out how to make it work for me (basically if i don't have the corresponding table already created in the DB, then Eclipse is unable to map the Entity type's members to columns in the database table and so far i dont know how to turn that error off. With Netbeans i did not get that issue and when i first ran my application the table was automatically created by hibernate as i declared it to do so by setting hibernate property with value "update"). Europa release supports JBoss 4.2.x release. Red Hat is also developing a comprehensive IDE solution for JBoss in partnership with Exadel to facilitate easier Rich web application development.

15 sorting algorithms visualized in 5 minutes, with awesome arcade sounds

15 sorting algorithms visualized in 5 minutes, with awesome arcade sounds from r/programming