Digging into the details of classloads has been on my list of research items for a while. I understand the concepts and the implications - what if a class gets loaded other than the one you intend to be running in your app and you're not really running the code you think you are?
Anyway...ran into this error today...
java.lang.LinkageError: loader constraint violation: when resolving method "[class]" the class loader (instance of [classloader1]) of the current class, [class], and the class loader (instance of [classloader2]) for resolved class, [class], have different Class objects for the type [class in conflict] used in the signature
Which led me to this great blog post which does a great job of epxlaining the nitty gritty of class loaders and potential issues with self-first and parent-first class loading...
Java Class Loaders
Nice.
Oh and by the way, I fixed this by changing the package of the class in my web app so it was different than the package of the conflicting class loaded by the web server. This may not be the right solution in all cases - you may want to remove the class from your web app and use the parent class or vice versa instead.
