How can I find the root cause of my never ending maven dependency hell?

Question

I have a maven java project in Eclipse IDE, and it needs to communicate with components on a weblogic server. When I first coded this, it worked without importing too many jars. However, I needed to make my project a part of a bigger assembly, and now my dependency requirements have gone out of control. I am still a little new to maven, and how it integrates with eclipse, but I've found that most of my ClassNotFoundExceptions points to classes that do exist, but with slight variances in path. See image below.

I suspect that I have imported a wrong library somewhere in the beginning of my dependencies, that now seems to be dependent on a great big tree structure of Classes that actually already exist, but with another path, and I'm stuck retrieving each of them individually, when they are already there...

Just look at the image: I have com.sun.xml.internal.bind.marshaller.SAX2DOMEx.class, but not com.sun.xml.bind.marshaller.SAX2DOMEx.class

Am I right in assuming that I am trying to fix symptoms, when I should focus on fixing the cause? If so, how can I retrace my imports, and find the root cause, in other words where I start importing the wrong jar?

Answer 1

@KjetilNordin,

You wrote:

I've found that most of my ClassNotFoundExceptions points to classes that do exist, but with slight variances in path

This suggests that somewhere along the way, one or more of the jars you depend on has 2 conflicting versions, between which the class moved between different packages. Maven's dependency resolution mechanism is resolving the jar to the version where the class sits in a different package from where you expect.

Run mvn dependency:tree on your project to see the entire hierarchy of transitive dependencies organized so you can track what depends on what. You'll likely see your jar come up in multiple locations, and presumably the wrong version is getting precedence in terms of Maven version resolution.

Next decide which version you want to go with.

Finally, add a <dependencyManagement> block in your pom.xml file to force the version to match your desired version.

Hope that helps.