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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: JSP class loader
Date Fri, 21 Jul 2006 16:21:21 GMT
Nikita,

> I work on application which allows user to deploy/undeploy large number of
> the JSP pages to AppServer (JBoss 4.03sp1 + Tomcat 5.5). Standard Tomcat
> class loader caches classes for all deployed JSP internally and never clean
> its cache. This brings JVM to PermGen overflow error after several days of
> system work.

Ouch. Are you saying that the sheer number of classes in your system is
overflowing your memory? That doesn't seem likely.

After tomcat compiles your JSP, it loads the resulting class and
executes it like a servlet.

If you have an option enabled, it will detect updated JSPs, re-compile
them, and reload them. It is certainly possible that when this happens,
Tomcat discards the entire ClassLoader and starts fresh. In that case,
if you have 10,000 JSPs, then each time you reload, you'll get 10,000
more classes loaded into memory. If this happens enough times, you'll
run out of memory since Java does not clean up old, unused classes in
memory.

Is this the behavior you are describing? If so, then you can't fix the
problem by writing your own JSP compiler and/or ClassLoader. Your best
bet is not to modify your JSPs and have them re-loaded.

Is this in a development setting or production? I would say that having
JSP reloading turned on in production is a mistake.

-chris



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