Hi, I think your concerns are addressed by JSR 277 (http://jcp.org/en/jsr/detail?id=277), scheduled for JDK 7.0 (!).
Tomcat does some kind of filtering (if you put servlet.jar in WEB-INF/lib) but I think the scope for this filtering is well defined (or at least restricted). Two years ago, I attended a BOF from the SAP guys that work on JMX and the SAP J2EE application server, and they showed in few slides that their app server was able to do jar versioning for applications (which is related to the issues raised). Don't know the details, but it may be a place to start to look for information. JSR 277 also gives few ideas about its scope and implementation, and I don't see ASF in the expert group members. This may be of interest as well (jar sealing and package access): http://java.sun.com/developer/JDCTechTips/2001/tt0130.html Long ago a project at CodeHaus, ClassWorlds if I remember well, was about writing a super classloader with features that would have possibly allowed versioning and merging. Don't know the actual status of that project. Considering the ClassLoader leaks chase Dain has done recently, I would say it's a delicate issue to play with the current classloader scheme :) Regards, Simon
