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From "Stephen Davidson" <stephen.david...@etcc.com>
Subject RE: different versions of jars within EAR/WAR/EJB module
Date Sun, 21 Feb 2010 20:03:49 GMT
Yes & no.

Keep in mind, in general you have multiple classloaders running when
deploying an Ear (for JBoss, you have to set its classloading policy to
STRICT).

The Jars will have their own classloader, with its own (isolated
classpath), same with the WARs and EAR.  Jars & Wars will both have a
dependency on the EAR classloader, and inherit anything the EAR knows
about.  So, anything declared in the EAR's Lib directory will be
globally available.  But in the case of Jars and Wars, especially when
they and their dependencies are in the EAR Root directory (EJB Jars,
anyone?), you have to specifically list the jars they depend on in the
MANIFEST Class-path entry.  Using this mechanism, one can safely use
different versions of a library jar in the same Ear (just keep them out
of the EAR/lib directory) for different Jars & Wars.  It may take some
experimenting to "fine tune" stuff, as well as some additional research.

-Steve


-----Original Message-----
From: Karsten Ohme [mailto:koh@mms-dresden.de] 
Sent: Sunday, February 21, 2010 1:54 PM
To: users@openejb.apache.org
Subject: Re: different versions of jars within EAR/WAR/EJB module

Am 21.02.2010 20:27, schrieb Stephen Davidson:
> Hi Karsten.
>
> I also forgot to mention;
>
>             <!--  Make the test class available for deployment -->
>             <plugin>
>                 <groupId>org.apache.maven.plugins</groupId>
>                 <artifactId>maven-jar-plugin</artifactId>
>                 <version>2.2</version>
>                 <configuration>
>                     <archive>
>                         <manifest>
>                             <addClasspath>true</addClasspath>
>                         </manifest>
>                     </archive>
>                 </configuration>
>             </plugin>
>
> This will allow your jars to use their version specific dependencies.
> If you are deploying your test jars as well, you will need to set the
> Executions section of the plugin.  
>   

But this does not affect the class loader, right? So any class loaded
first/last will be taken?

Regards,
Karsten
> -Steve
>
> -----Original Message-----
> From: Karsten Ohme [mailto:koh@mms-dresden.de] 
> Sent: Sunday, February 21, 2010 12:26 PM
> To: users@openejb.apache.org
> Subject: Re: different versions of jars within EAR/WAR/EJB module
>
> Am 21.02.2010 19:15, schrieb Karsten Ohme:
>
> I had the idea that for the dependency conflicts the dependency
overview
> of the super pom can help. Usually Maven plugins have support for
this.
>
> For the convergence of used versions the site report of maven can
help,
> e.g.
>
> http://microlog.sourceforge.net/site/dependency-convergence.html
>   
>> Hi Stephen,
>>
>> but how have you found out, which libraries are used by sub libraries
>> and solved this?
>>
>> E:g I have Foo.jar using commons-lang-2.3 and Bar.jar
>>     
> commons-lang-2.4.
>   
>> Now I only want to have one one the commons-lang. One way is to strip
>> away the version so an already used one is overwritten, but I'm not
>>     
> sure
>   
>> if this always works if the API has changed.
>>
>> Maybe there is some version aware class loader out there which can
>>     
> load
>   
>> from class information the right one.
>>
>> Regards,
>> Karsten
>> Am 21.02.2010 18:36, schrieb Stephen Davidson:
>>   
>>     
>>> Hi Karsten.
>>>
>>> I had this problem as well, especially my project uses multiple
wars.
>>>       
> I
>   
>>> researched "skinny wars", and found a solution.  In a nutshell, you
>>>       
> have
>   
>>> jars & wars declare all shared dependencies (such as
commons-logging,
>>>       
> or
>   
>>> whatever third-party library has this as its dependency) with scope
>>> "provided".  You can do this by default be declaring your shared
>>> dependencies at the parent pom level.
>>> Then, in the EAR's pom, I redeclared the dependency, without the
>>> "provided" scope.  The only annoying thing was when I had to
>>> automatically provide some jars on a EAR wide level.  I had to add
>>>       
> the
>   
>>> following section;
>>> <groupId>org.apache.maven.plugins</groupId>
>>> <artifactId>maven-ear-plugin</artifactId>
>>> <!-- configuring the ear plugin -->
>>> <configuration>
>>> <!-- (one for each jar to had to have its classes automatically
>>> available, dependency MUST be explicitly declared in the pom's
>>> dependency section) -->
>>>   <jarModule>
>>>     <groupId>groupId</groupId>
>>>     <artifactId>shared</artifactId>
>>>     <bundleDir>lib</bundleDir>
>>>   </jarModule>
>>> </configuration>
>>> <plugin>
>>>
>>> Regards,
>>> Steve
>>>
>>> -----Original Message-----
>>> From: Karsten Ohme [mailto:koh@mms-dresden.de] 
>>> Sent: Sunday, February 21, 2010 11:16 AM
>>> To: users@openejb.apache.org
>>> Subject: different versions of jars within EAR/WAR/EJB module
>>>
>>> Hi,
>>>
>>> I have the following problem:
>>>
>>> I'm using different utility libraries which are using also different

>>> versions of e.g. Apache-commons libraries. Now some libraries are
>>>       
> used
>   
>>> in different versions. So, I have possibly some default library
>>>       
> versions
>   
>>> in the application server and some library versions in my ear and
the
>>> ear can also include different library versions.
>>> Which library wins? Until now somehow this always worked, but now I
>>>       
> had
>   
>>> the problem with different versions. I received strange exceptions
>>>       
> while
>   
>>> using different versions together.
>>>
>>> How can this problem be solved? Do I have to exclude in my Maven
>>> configuration all duplicates manually?
>>>
>>> Regards,
>>> Karsten
>>>
>>>   
>>>     
>>>       
>>   
>>     
>
>   


-- 
Karsten Ohme
T-Systems Multimedia Solutions GmbH
Portal Technologies, Applications & Appliances
Hausanschrift: Riesaer Strasse 5, 01129 Dresden
Postanschrift: Postfach 10 02 24, 01072 Dresden
Telefon: +49 351 28 20 - 2123
Fax: +49 171 351 28 20 - 5116
E-Mail: karsten.ohme@t-systems.com 


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