[opencms-dev] Different version jars in lib folder

[Achim Westermann]

Hi Paul,

> You're absolutely right, and memory serves you well - they were 334 bytes indeed.

Uuuuh.... Yesssss!

>  From what you say, I gather it's risky to have different versions of OpenCms on the same Tomcat, then? (Since they may employ different version jars, which could cause conflict?)

I'd consider it a bug if tomcat runs into Classloading errors if several 
OpenCms versions are deployed to different webapplications. But I am not 
sure now if there might be a special case where this might happen. The 
mechanism of classloading is explained here: 
http://tomcat.apache.org/tomcat-6.0-doc/class-loader-howto.html

HTH,
Achim

> Cheers,
> Paul
>
>> -----Original Message-----
>> From: opencms-dev-bounces at opencms.org
>> [mailto:opencms-dev-bounces at opencms.org] On Behalf Of Achim Westermann
>> Sent: 14. april 2011 22:41
>> To: The OpenCms mailing list
>> Subject: Re: [opencms-dev] Different version jars in lib folder
>>
>> Hi Paul,
>>
>>> For example, all of these:
>>> lucene-core-1.9.1.jar
>>> lucene-core-2.1.0.jar
>>> lucene-core-2.2.0.jar
>>> lucene-core-2.3.1.jar
>>> lucene-core-2.3.2.jar
>>> lucene-core-2.4.1.jar
>>
>> Most often this is the case for OpenCms installations that have
>> undergone at least one update. The setup routine will
>> overwrite previous
>> libraries with an empty jar file (size something like 334
>> bytes, don't
>> have this in memory) because in the past deletion of jar files failed
>> under some circumstances. It's OK to delete all the tiny jar files.
>>
>>> (Most of the commons-xxx jars, and a bunch of others as
>> well, are also
>>> present in multiple versions.)
>>> What could be the cause of all these multiple versions? Is
>> it safe to
>>> delete the older versions and just keep the most recent?
>>> On a side-note:
>>> Can two different versions of the "same" jar cause
>> conflicts, if they
>>> reside in the separate webapps' lib folder?
>>> For example:
>>> webapp_one/WEB-INF/lib/mylibrary-v1.0.jar
>>> webapp_two/WEB-INF/lib/mylibrary-v2.0.jar
>>
>> Indeed this can cause ClassCastExceptions. It's a matter of luck in
>> which order the jar files are loaded by the ClassLoaders. Duplicate
>> non-empty jar files have to be deleted as you described.
>>
>> HTH,
>>
>> Achim
>>
>>
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