Classloading in Websphere Administrative Console
I have this web service server application which has been running fine at a Websphere Process Server. One day, my application's log was writing to another application B's log. That is really weird. I checked and found out that this B was recently deployed to the server only. The cause for my application to write to B's log is due to B's log4j jar file was put in the server's common directory ! If we do not change the classloading policy, which is default to PARENT_FIRST, then Wepshere's classloader will load that common directory first only will load the jars in our application's WEB-INF/lib directory.
Hence i logged on to Websphere Administrative Console, went to my application's war file and changed the classloader policy to PARENT_LAST. By doing this Websphere will find and load the neccessary classes from your web module's WEB-INF/lib(web module classloader) first, also you must ensure that the jars you put under your application's WEB-INF/lib folder do not clash with the one at server's common directory, else you will get a java.lang.LinkageError exception due to classloader is trying to load duplicate class.