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From Venkata Pavan Kumar Sannisetty <sunny...@gmail.com>
Subject Re: ClassNotFoundException Error in Tomcat 5.5 and Tomcat 6.0
Date Sun, 10 Jun 2012 18:11:16 GMT
Hi Konstantin Kolinko,

Thanks for the response.

Can you point out some reference where i can know about this permgen memory
leak. I am unable to find good article/material on it to understand furthur.

Thanks,
Pavan.

On 10 June 2012 06:59, Konstantin Kolinko <knst.kolinko@gmail.com> wrote:

> 2012/6/10 Venkata Pavan Kumar Sannisetty <sunnypav@gmail.com>:
> > I am having this strange issue with the tomcat 5.5 and tomcat 6.0
> servers.
> > I have two web applications which will be installed on tomcat.When tomcat
> > is started these two web applications also get started simultaneously but
> > sometimes one web application fails to initialize because of the init
> > failure in one application another application is getting
> > classnotfoundexception errors while running. In tomcat 7.0 the
> application
> > is running fine even if the other application failed to initialize.
> >
> > After some debugging i came to know there is one jar named crystal.jar
> > which is in the web-inf/lib folder of both applications. I have moved the
> > jar to common/lib folder of tomcat then it started working fine. I want
> to
> > know why it is working fine in tomcat 7.0 not in tomcat 5.x and tomcat
> 6.x
> > versions. Is there any change in classloading architecture between these
> > versions ?
>
> Guessing on a crystal jar^H^H^H ball,..
>
> There exist a known kind of PermGen memory leaks, when a library class
> is referenced by a system class and thus lives beyond its age. One
> example is when Java discovers a JDBC driver, or some other service
> and "automatically registers" it. It keeps reference to it in a
> system, but the class itself belongs to the web application and has to
> be unloaded when application stops - but cannot, because of that
> reference.  Not all such references are easy to clear.
>
> One typical symptom in such a case is that the first web application
> that relies on this system feature will succeed,  but the second and
> other ones will fail  (because the service that is registered in the
> system belongs to first web application  and cannot see classes from
> classloader of the second application and vice versa).
>
> Tomcat 7 and recent versions of Tomcat 6 have better protection
> against certain known PermGen memory leaks in their default
> configuration.
>
> Tomcat 5.5 does not have such protection at all.
>
> Best regards,
> Konstantin Kolinko
>
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