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Posted to users@tomcat.apache.org by Andrew Hole <an...@gmail.com> on 2007/10/10 16:45:32 UTC
Different jar version
What happens if I put different jar versions of same classes on WEB-INF/lib?
Example:
project.jar (new version)
project_old.jar (old version)
Tomcat load and use both? Could Tomcat be confused with this situation?
Thanks a lot
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RE: Different jar version
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: Andrew Hole [mailto:andremailinglist@gmail.com]
> Subject: Re: Different jar version
>
> I'm getting OutofMemoryError ... Could have some relationship having
> two different versions of jar and memory leak?
Not likely, but it really depends on how your classes interact.
Instead of indulging in rather pointless speculation, why not fix the
obvious error by removing the redundant jar and see what happens?
- Chuck
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Re: Different jar version
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Andrew,
Andrew Hole wrote:
> I'm getting OutofMemoryError ... Could have some relationship having
> two different versions of jar and memory leak?
It's very unlikely. As other posters have said, either one class gets
loaded or the other one does, not both. The effect is as if the other
one were not available at all. Therefore, the memory leak is unlikely to
be related to the duplicate JARs.
- -chris
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Re: Different jar version
Posted by Andrew Hole <an...@gmail.com>.
I'm getting OutofMemoryError ... Could have some relationship having
two different versions of jar and memory leak?
Thanks
On 10/10/07, Caldarale, Charles R <Ch...@unisys.com> wrote:
> > From: Andrew Hole [mailto:andremailinglist@gmail.com]
> > Subject: Different jar version
> >
> > What happens if I put different jar versions of same classes
> > on WEB-INF/lib?
>
> Really Bad Things.
>
> > Could Tomcat be confused with this situation?
>
> Yes, as is the person who did such a thing.
>
> Depending on the order the jars happen to show up in the directory (the
> real directory, not the sorted one shown by ls or dir commands), one
> will likely take precedence over the other, but you can't predict which
> that will be. This is a Very Bad Idea.
>
> - Chuck
>
>
> THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
> MATERIAL and is thus for use only by the intended recipient. If you
> received this in error, please contact the sender and delete the e-mail
> and its attachments from all computers.
>
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RE: Different jar version
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: Andrew Hole [mailto:andremailinglist@gmail.com]
> Subject: Different jar version
>
> What happens if I put different jar versions of same classes
> on WEB-INF/lib?
Really Bad Things.
> Could Tomcat be confused with this situation?
Yes, as is the person who did such a thing.
Depending on the order the jars happen to show up in the directory (the
real directory, not the sorted one shown by ls or dir commands), one
will likely take precedence over the other, but you can't predict which
that will be. This is a Very Bad Idea.
- Chuck
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
MATERIAL and is thus for use only by the intended recipient. If you
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Re: Different jar version
Posted by David Delbecq <de...@oma.be>.
The question is better
"what happen if you have 2 classes with same name and package in the
same classloader?"
Knowing which of both classes will be indeed loaded and used when need
is undetermined. Only one of those classes will be used, but it there is
no rule as to which will be used. This is mainly depended on the order
at which tomcat looks at .jar which itself is dependent on order in
which filesystem returns them, which depend on os, date, filename, etc.
En l'instant précis du 10/10/07 16:45, Andrew Hole s'exprimait en ces
termes:
> What happens if I put different jar versions of same classes on WEB-INF/lib?
> Example:
> project.jar (new version)
> project_old.jar (old version)
>
> Tomcat load and use both? Could Tomcat be confused with this situation?
>
> Thanks a lot
>
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>
--
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Re: Different jar version
Posted by Tim Funk <fu...@joedog.org>.
It uses the first version of the class it finds when findClass is
called. First version depends on which jar it looks in first. There is
no defined order in which jars should be read first. So the behavior of
Tomcat would be like any other java application - unknown.
-Tim
Andrew Hole wrote:
> What happens if I put different jar versions of same classes on WEB-INF/lib?
> Example:
> project.jar (new version)
> project_old.jar (old version)
>
> Tomcat load and use both? Could Tomcat be confused with this situation?
>
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RE: Different jar version
Posted by Peter Crowther <Pe...@melandra.com>.
> From: Andrew Hole [mailto:andremailinglist@gmail.com]
> What happens if I put different jar versions of same classes
> on WEB-INF/lib?
> Example:
> project.jar (new version)
> project_old.jar (old version)
>
> Tomcat load and use both? Could Tomcat be confused with this
> situation?
Each time a class is requested, the classloader looks through the jars
until it finds a class with that name, then immediately loads the one it
finds. There may be other copies in other jars; they are not loaded.
To my knowledge*, there's no way of knowing in advance in which order
Tomcat will look through the jars. If you have two classes with the
same name, you have no way of knowing in advance which one will be
loaded. Tomcat won't be confused, but you sure will be if you have
different versions of the same classes in different jars :-).
- Peter
* As always, happy to be corrected by those who know better!
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