Sunday, March 11, 2007
JPA + J2SE Servlet Containers = Impossible
Well, somewhat impossible depending on what you need to do.
If you need dynamic weaving of your classes at runtime, give up. It won't work, not with a J2SE servlet container.
The problem seems to be that the javaagent (for both OpenJPA and for Toplink Essentials) is incapable of coping with classes that are loaded by a different classloader. If you manage to get your javaagent JVM argument to work (which will require annoying experiments with quotation marks and adding stuff to your classpath), then all of your Entity classes will fail to load because the agent can't find them. They don't exist as far is it is concerned, because they are loaded by a different classloader.
So if you want to use lazy loading of 1:1 fields with a J2SE container, you must either do static weaving or give up hope. Your other option is to use a full-blown J2EE container in all its bloated glory.
Screw this. I'm going to bed.
If you need dynamic weaving of your classes at runtime, give up. It won't work, not with a J2SE servlet container.
The problem seems to be that the javaagent (for both OpenJPA and for Toplink Essentials) is incapable of coping with classes that are loaded by a different classloader. If you manage to get your javaagent JVM argument to work (which will require annoying experiments with quotation marks and adding stuff to your classpath), then all of your Entity classes will fail to load because the agent can't find them. They don't exist as far is it is concerned, because they are loaded by a different classloader.
So if you want to use lazy loading of 1:1 fields with a J2SE container, you must either do static weaving or give up hope. Your other option is to use a full-blown J2EE container in all its bloated glory.
Screw this. I'm going to bed.
Labels: j2ee, javaagent, JPA, servlet, software, weaving
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