Tobias: I couldn't agree more with your last paragraph. Unfortunately I don't have the luxury of choosing a different framework. I'm working on a fairly substantial J2EE application that we are preparing to release as Open Source, trying to get it to build and run cleanly under NetBeans so that it is possible for other people to modify it easily - the current configuration and build mechanisms are arcane to say the least. I'm a maintenance programmer, for the purposes of this project, and it is a complete nightmare. Apart from the fact it uses two different J2EE frameworks (yes, really) and over 50 different external JAR files, the thing is an XML configuration file nightmare. All the tools that my IDE provides are useless as so much of the application structure is in XML files.
Kawazu: I agree that some things are OK in configuration files - paths, URLs and so forth. The problem is that the most significant parts of the application logic are in various XML files. As I already said, this renders most of the tools I have for grokking the application useless. I don't believe that Spring+AOP+XML does keep the code "clean", all it does is hide the messy bits in XML files - it's still a mess, but it is now a mess that is split over two different technologies, Java and XML, and two technologies that have a huge "impedance mismatch". I'd actually prefer to have all the configuration done in POJC (Plain Old Java Code), because that's what the XML goop actually ends up as anyway, and at least if it is Java I can use debuggers and code inspectors on it. I just don't understand what benefits XML is supposed to have - I can't think of anything that can be done in XML that couldn't be done in Java.