[Studio] Fixing class loader issues between Eclipse plugins using "Buddy Class Loading"

[Pierre-Arnaud Marcelot <pa...@marcelot.net>]

Hi all,

While I was developing the Apache DS plugin for Apache Directory Studio, I
ran into several class loader issues.

The Apache DS plugin defines a new Log4J appender that is used to display
the logs of an Apache DS server in the a console inside Studio.
In the Apache DS plugin, the Log4J dependency is inherited from the Apache
Directory Studio Jars plugin which contains the Log4J jar dependency and
re-exports it in its MANIFEST.MF file.
The compilation worked fine, but at runtime I had some ClassNotFound
exceptions when I was trying to create a new instance of the Logger.
Basically the problem was that the two plugins (Apache DS and Jars) are not
sharing the same class loader, even if we explicitely re-export the
dependency.
So, the Log4J class in the Jars plugin class loader could not find my
Appender class that was in a separate class loader (the Apache DS plugin
class loader).

After a few researches on google, I finaly found that I had to use the
"Buddy Class Loading" feature of Eclipse to get my code working at runtime.

I though it could be interesting to share the links that helped me solve
this problem if someone working on Studio faces a similar issue.

http://www.eclipsezone.com/eclipse/forums/t61831.html
http://www.eclipsezone.com/articles/eclipse-vms/

Regards,
Pierre-Arnaud

Re: [Studio] Fixing class loader issues between Eclipse plugins using "Buddy Class Loading"

[Stefan Seelmann <se...@apache.org>]

Hi Pierre-Arnaud,

thanks for sharing your experience and the links.

Regards,
Stefan


Pierre-Arnaud Marcelot schrieb:
> Hi all,
> 
> While I was developing the Apache DS plugin for Apache Directory Studio,
> I ran into several class loader issues.
> 
> The Apache DS plugin defines a new Log4J appender that is used to
> display the logs of an Apache DS server in the a console inside Studio.
> In the Apache DS plugin, the Log4J dependency is inherited from the
> Apache Directory Studio Jars plugin which contains the Log4J jar
> dependency and re-exports it in its MANIFEST.MF file.
> The compilation worked fine, but at runtime I had some ClassNotFound
> exceptions when I was trying to create a new instance of the Logger.
> Basically the problem was that the two plugins (Apache DS and Jars) are
> not sharing the same class loader, even if we explicitely re-export the
> dependency.
> So, the Log4J class in the Jars plugin class loader could not find my
> Appender class that was in a separate class loader (the Apache DS plugin
> class loader).
> 
> After a few researches on google, I finaly found that I had to use the
> "Buddy Class Loading" feature of Eclipse to get my code working at runtime.
> 
> I though it could be interesting to share the links that helped me solve
> this problem if someone working on Studio faces a similar issue.
> 
> http://www.eclipsezone.com/eclipse/forums/t61831.html
> http://www.eclipsezone.com/articles/eclipse-vms/
> 
> Regards,
> Pierre-Arnaud
> 
>