If the class to override is called com.example.FooServlet and this class is inside a jar WEB-INF/lib/foo.jar, how to override it with a class also called com.example.FooServlet in another jar, say bar.jar?
Or is there any way to make sure the one in bar.jar is loaded first?
Making bar.jar a module is no-go because the FooServlet imports tons of classes from many jars in WEB-INF/lib.
As I stated above, I tried to contain bar.jar in a module, but got class not found or no class def error (can't remember clearly) as FooServlet extends/implements some extra classes/interfaces which are in 3rd party jars in WEB-INF/lib.
I'm not allowed to touch foo.jar or any of the jars that are already existing in WEB-INF/lib.
You said you cannot touch existing jars, and you seem to imply you can add a jar of yours to WEB-INF/lib.
According to this:
- there is no specified order of precedence for jars under
WEB-INF/lib/*.jar.
So if you addbar.jarin there, you don't know if it will be loaded before or afterfoo.jar. - the servlet spec says classes under
WEB-INF/classesmust be loaded before anything underWEB-INF/lib/*.jar
Assuming you can add a jar under WEB-INF/lib, you should be able to add a class (or several) under WEB-INF/classes, without touching the ones in place.
So, if you want the classes from bar.jar to be loaded first, you can unzip the contents of that jar under WEB-INF/classes instead (or just the class you want to be loaded in priority -- for example WEB-INF/classes/com/example/FooServlet.class).