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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: Problems with ImageIO
Date Wed, 07 Apr 2010 20:47:02 GMT
> From: Thad Humphries [mailto:thad.humphries@gmail.com]
> Subject: Re: Problems with ImageIO
> 
> (1) This leak situation may arise when I use "stop" or 
> "reload" on my webapp.

Correct.  The JRE keeps a global imageio registry with a reference to a webapp-specific class,
resulting in a slow PermGen memory leak.

> (2) It can also be prevented by placing my JAI and JAI-IMAGE
> I/O jars in CATALINA_HOME/lib or JAVA_HOME/jre/lib/ext vs my
> WEB-INF/lib.

Also correct, since the classes will now be loaded by a global classloader, rather than a
webapp-specific one.

> I prefer to keep the jars in my WEB-INF/lib as it's less 
> intrusive to the server manager.

Which includes being easier for anyone installing your webapp.  Unfortunately, you have to
pick one poison or the other, since Sun mostly ignored their servlet-spec-required isolation
of webapps when designing the numerous global registries.

I suppose you might try a ServletContextListener that deregisters the JAI classes when your
webapp is being shut down.

 - Chuck


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