BEA WL9.2 NoClassDefFoundError when instantiating class in EAR library

Question

I'm having a problem in BEA Weblogic 9.2 with a NoClassDefFound error that has me stumped.
To test the problem, I created a very simple web service project and the associated EAR project which is then deployed to a simple domain. Within the web service project I defined an Interface, and then a class that implements that interface. I have a single web method which when called uses the Class.forName() method to instantiate an instance of the implementing class and then run the sayHello method of the class. This all works great, as it should.
Next I created a new java project which contains another class which implements the interface defined in the webservice project. I built this class into a jar file, and added the jar file into the EAR project library directory so that it shows up as a referenced library to the web service project. In the original web method I added code to again use the Class.forName() method to this time get an instance of the implementing class defined in the jar file. When I run the method this time, a java.lang.NoClassDefFoundError is thrown trying to instantiate the new class. I thought that because the jar file with the class is included in the project EAR, that the web service would see that class in it's classpath, but clearly that's not happening. I have a feeling I'm probably forgetting something real simple, but I can't figure out what it could be right now.
Any help solving this problem would be greatly appreciated. Thanks in advance.

Answer 1

Thanks for the suggestions, unfortunately I'm still struggling with the problem.
First, let me clarify a couple of things brought up by the other posters. The jar file containing my implementation of an interface is being placed in the EAR's APP-INF/lib directory. I'm developing the test program in Weblogic Workshop 9.2. Workshop is built around an earlier version of Eclipse so in most ways I am using Eclipse as a development tool, but only through the official Weblogic Portal 9.2 release that includes Workshop. I am not using the 'Oracle Enterprise Pack for Eclipse'. What I am trying to do gets a bit confusing to explain, but in reality is a very simple thing that I find hard to believe is causing me problems. The reason I posted this problem in the Weblogic Server forum is that what I'm trying to do works perfectly if I'm just using multiple java projects importing implementing classes from other jars. The problem only occurs when I move the problem into a web service project.
As I've done some more experimenting I've found some more interesting behavior. I created a new Interface in the library project, as well as an implementation of this new interface. Again I copied this library into the EAR's APP-INF/lib directory, and then in the webservice project created another class that implements the new interface. Back in my web-method, I added code to try and instantiate instances of each of the new implementing classes. Works perfectly. The problem only occurs when the Interface is defined in the webservice and the implementing class is defined in the library. All other instances seem to work fine. The error thrown is a NoClassDefFoundError, and the class that it says it can't find is the Interface class. Again, the Interface class is defined in the webservice src, and the application has no trouble finding that class if I try and instantiate an implementing class that is also defined in the webservice src. It's only when I try and instantiate a class defined in a referenced library that the error occurs.
This should be a very easy problem to re-create, and I have a test project that I can provide if anyone's willing to take a look. Again, any help or suggestions would be greatly appreciated.