Classpath tools : jcfind and JWhich

Deep understanding of Java classpath is something that is too often neglected. I won’t write an article about classpath, internet is full of readings about it :

• How Classes are Found at java.sun.com
• Classpath (Java) page from Wikipedia
• Classpath entry in the Java Glossary
• Java Tip 105: Mastering the classpath with JWhich

Here come JWhich and jcfind. Both are classpath reflection tools.

JWhich provides a command line interface and a Java api where jcfind only has command line interface and is written in python.

I prefer to use jcfind from the command line because it’s really faster than Which4j and the command line is more practical. In Java software, I use the JWhich API that is really easy to use. The big drawback of using Which4j from command line is that you must provide a full class name, using it’s API you can search for a class simple name.

Glassfish, Hibernate and WebServices - WSGEN Classpath

Following my quick and dirty how-to about using hibernate in glassfish I came across a small pitfall when dealing with metro webservices.

The glassfish’s wsgen classpath on Glassfish is not by domain, ie. the wsgen tool is not run in the domain class-loader.

When trying to deploy a webservice that returns an entity with a hibernate annotation, I got this following error :

Server logs showed the following trace :

/home/paul/Programs/glassfish-v2-b58g/domains/domain1/applications/j2ee-apps/ear-0.1-SNAPSHOT/lib/entities-0.1-SNAPSHOT.jar(app/model/entities/User.class):
        warning: Cannot find annotation method 'value()' in type 'org.hibernate.annotations.Fetch':
        class file for org.hibernate.annotations.Fetch not found
Problem encountered during annotation processing;
see stacktrace below for more information.
java.lang.NullPointerException
        at com.sun.tools.ws.processor.modeler.annotation.WebServiceAP.isSubtype(WebServiceAP.java:360)
        ...... SNIP ......
        at com.sun.enterprise.management.deploy.DeployThread.run(DeployThread.java:223)
error: compilation failed, errors should have been reported
Exception occured in J2EEC Phase
com.sun.enterprise.deployment.backend.IASDeploymentException: WSGEN FAILED
        at com.sun.enterprise.webservice.WsUtil.genWSInfo(WsUtil.java:2

Adding the hibernate-annotations.jar file in the glassfish main lib/ directory added the necessary classes to the wsgen classpath.

Unit test JPA Entities with in-memory database

Still about Hibernate, I have several JPA Entities grouped in a Persistence Unit that I need to test. So here is another quick and dirty howto titled “Unit test JPA Entities with in-memory database”.

Here I assume you already have written your entities java classes with correct annotations.

As I’m working with embedded Derby for a year, I first tried with it but procton (thank you procton) pointed me to another lightweight RDBMS.

So, in this how-to we will set up a unit-tests dedicated persistence unit and use HSQLDB as in-memory database for unit tests.

Building an EJB3 app using GlassFish v2, Maven2 and NetBeans 6

In an article explicitly titled Building an EJB 3.0 application using GlassFish v2, Apache Maven 2 and NetBeans IDE 6.0, Jacek Laskowski explain in detail how Netbeans 6 can be used by maven users willing to use GlassFish as an EJB3 container.

I’m currently doing these type of things with Netbeans 6 but I didn’t know it was feasible with so few command line maven invocations.

Quick and dirty howto : Use Hibernate in Glassfish V2

For my first post here I’ll write a quick and dirty howto for using Hibernate inside the Glassfish V2 container.

1. Download Hibernate projects
2. Put’em in the domain’s lib dir
3. Change your persistence.xml file
4. Enjoy

Details are following :