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From M4N - Arjan Tijms <>
Subject RE: Occasional NoClassDefFoundError, but disappears after couple of restarts
Date Fri, 24 Jul 2009 15:49:59 GMT
> This kind of error can be caused by having the same class(es) in multiple locations in
a given
> branch of the classloader tree, such as in both a webapp's WEB-INF/lib and in Tomcat's
> directory (or on the system classpath).  Have you checked that?
Well, that's indeed a good suggestion. We added 3 libraries to [tomcat 
install dir]/lib, namely activation.jar, mail.jar and 
postgresql-8.3-603.jdbc3.jar. As it happens the web application's 
WEB-INF/lib does contain a postgresql-8.3-603.jdbc4.jar. This last .jar 
should of course not be there.

I have indeed seen applications on Jboss AS fail due to duplicate class 
definitions. The odd thing is that on Jboss AS it would fail both on 
localhost and on the production server, but in the case of Tomcat it 
only fails on the production server. Also, these (nearly) duplicate jar 
files seem to have been there for some time and restarts only started 
recently to fail on a regular basis. A recent upgrade from JDK 6 update 
6 to update 12 seems to be most likely candidate for causing the sudden 
change in behavior.

I'll remove the duplicate .jar, and hopefully the next restarts will 
happen smoothly again.

Thanks again for your reply.


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