one of the more frustrating aspects of working with WebSphere is when something works on a simple servlet container - it doesn't necessarily on WebSphere.
although the app is the same, it's not exactly the same under the covers. one common issue is loading classes and loading either old, conflicted or other problems. a very simple solution to this is to make your applications classes take precedence by switching the WebSphere classloading order. this is done in the following way
- go to the WebSphere console
- find your application and go into it's management screen
- select "Class Loading and update detection" (as of WAS 8)
- change the order of loading by select "Classes loaded with local class loader (parent last)"