During my tests with servlets I got a really confusing error message. After restarting Tomcat I tried to execute the servlet
and got the following screen:
I was confused, because the servlet-api.jar was included in the lib folder. To be sure, you can display the loaded classes by -verbose:class swicth.
Fix: Recompile your class in your eclipse environment. There seems to be a problem which leads sometimes to non proper compilations in eclipse.I was wondering about that, but I found some other blogs / boards where other people faced the same behavior.