Tip: Debugging JAXP Internals

In my latest battle with JAXP and Schema validation, I found out a little trick. It turns out, that implementation classes in JAXP use a debug flag to control stdout debugging. And this little flag is initialized from the system property jaxp.debug

So, starting your program, application server, … with -Djaxp.debug=true enables all sorts of initialization/bootstrap debug information, that can be helpful.