I think you are assuming the classloader org.something.DatabaseRequestHandler is using is the webapp's local classloader. I doubt this is the case. Those with more knowlege of the classloader architecture may chime in, but the classloader being used is most likely the shared classloader instead. If possible, move the handler.jar from shared/lib to WEB-INF/lib of your webapp and the problem should go away.
--David Christopher Piggott wrote: >I have something happening with class loading from within a server, and I >don't understand it. > >My servlet defines some classes called: > org.something.server -- the class that extends HttpServlet > org.something.DatabaseRequestHandler -- an interface > >When you make a request to the server, it figures out what handler class to >load. Then it attempts to load it: > > Class handlerClass = Class.forName(handlerClassNameString); > > >QUESTION: looking at the little diagram in the Tomcat 5.5 Class Loader HOW-TO, >when I do the above (Class.forName) I am using the Webapp class loader, >correct? > > >The handler classes are all in handlers.jar which is in >$CATALINA_BASE/shared/lib. The actual exception that I get is: > > 2006-04-28 17:05:55 StandardWrapperValve[xdb]: Servlet.service() for > servlet xdb threw exception > java.lang.NoClassDefFoundError: org/something/DatabaseRequestHandler > >It took me a few minutes to realize that this was not a ClassNotFound >exception, but something else. Reading docs I figured out that the most >probably cause is that the servlet's classloader was able to find the handler >class, but then it failed to load one of the things it depended on, >specifically it was able to find handlerClass but not the interface class that >it depends on. > >Trouble is: the interface .class file is right there in >WEB-INF/classes/com/something/DatabaseRequestHandler.class just like it should >be. So, I am stumped why the class loader would be able to find the handler >class in $CATALINA_BASE/shared/lib but NOT the interface that it implements >which is in WEB-INF/classes. > > >At the suggestion of a nice gentleman on freenode, I tried turning on the >-verbose:class option in the jvm, and watched it log some interesting stuff to >catalina.out. Unfortunately it doesn't shed any light on what is happening, >beyond the exception and stack trace in the error log. I don't want to post >the whole stack trace (unless someone thinks it would help to see it) but I >will say that it includes catalina.loader.WebappClassLoader as well as >catalina.loader.StandardClassLoader > >--Chris > > > > >--------------------------------------------------------------------- >To unsubscribe, e-mail: [EMAIL PROTECTED] >For additional commands, e-mail: [EMAIL PROTECTED] > > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
