JWS offline + JPA/Eclipselink fails

Question

Hi,
We're using JPA in our web start enabled application. We have the latest version of the Eclipselink jar (1.1.2).
When starting the application in online mode, everything runs fine, but we can see that the jar file containing META-INF/persistence.xml is downloaded several times at every startup.
When starting in offline mode, we run into a fatal error. It seems that eclipselink is always trying to get the persistence.xml file from the online resource.
Exception Description: An exception was thrown while searching for persistence archives with ClassLoader: com.sun.jnlp.JNLPClassLoader@8814e9
Internal Exception: Exception [EclipseLink-30004] (Eclipse Persistence Services - 1.1.2.v20090612-r4475): org.eclipse.persistence.exceptions.PersistenceUnitLoadingException
Exception Description: An exception was thrown while processing persistence.xml from URL: http://10.0.0.1/app/test.jar
Internal Exception: java.net.MalformedURLException
The same problem is described in this post, but I cannot see a definite solution: http://forums.sun.com/thread.jspa?threadID=5123126
Does anybody have an idea what can be done in this situation? Is it possible to somehow place the META-INF directory in classpath so that JWS does not try to get the resource online?
Thanks.

Answer 1

I think this is the same issue posted to yesterday in [t-5403895]. I eventually spent several hours tracking through the EclipseLink code to find out exactly what caused the problem. As you say, it's basically because EclipseLink is trying to load the resource from the web. This is because internally it resolves the reference to a URL starting with "http", and assumes it must be a server resource. In online JNLP mode, it downloads the file several times, in offline mode it fails. The "correct" action is to use the JNLP classloader to getResource() on META-INF/persistence.xml. Obviously, and perhaps understandably, EclipseLink (or TopLink Essentials as was) was not written or tested with Java Web Start offline mode in mind.
I did finally make this work, but only by modifying two EclipseLink classes, which is not ideal. If you're willing to entertain that option, please post again and I'll provide details.