Websphere classloader delegation mode

Question

We are using WebSphere 6.1 application server with default classloader delegation mode i.e. PARENT-FIRST. We think about changing it to PARENT-LAST to be able to choose our jsf implementation or our webservices stack.

As PARENT-FIRST is the default I wonder how many people switched to PARENT-LAST, and what was the reason to switch, and if your life became better since you switched :)

We have a lot of applications in production so I cannot just switch to see what happens, if we do it we will have a lot of testing so I’d like to have to some feedback if you have switched to PARENT-LAST.

Thanks

Answer 1

On projects that I'm assigned to, we actually do switching to PARENT-LAST for most of our applications. The reason for that is usually an app-specific implementation of something, or a need for app-specific property bundle that Websphere uses too (overriding the Websphere setup of commons-logging, for example).

If something breaks after the switch, it is usually because of somewhat wrong setup of the application that suddently starts to be used (while before the switch it was overriden by Websphere's resources).

Answer 2

Portlet applications (deployed on WebSphere Portal Server) always switch their configuration to parent last. In my experience it is always better to switch to parent last, especially if you are using commons logging. This is because WebSphere includes a truck load of stuff in its own classloaders which are often a different versions/configurations to the one that you want to use.

If you are doing it, I would recommend that you script up the deployment of the application because it can be one of those things that are missed when you do a deployment.