Java Update jetty from Version 8 to 9.2.7: exception "Multiple Servlets to path"

I updated my jetty from 7 to 8. At the moment I'm trying to update from Version 8 to 9. I can't reach the webpage and there is an error:

    org.eclipse.jetty.webapp.WebAppContext - Failed startup of context o.e.j.w.WebAppContext@16c1863{/,file:"/path/to/workspace/project"/webapp/,STARTING}{./webapp}
    java.lang.IllegalStateException: Multiple servlets map to path: /V/administration.cache/app/*: "Vaadin Servlet"    

Changed paths and packages are tagged by ".

I found out, that there was a bug, which should be fixed now.

Is this caused by a Bug or is there a possibility to solve it with other methods and classes from Version 9. A change of the paths is not possible.

Thanks to everyone, who could help.

Solution

Your webapp, has multiple declarations for the same url-pattern.

Namely /V/administration.cache/app/*

That means your webapp's declaration is bad, and can produce unpredictable results.

What's likely happened is that your move from Jetty 7 which was simple with its declaration handling (Servlet 2.5, only used WEB-INF/web.xml) to Jetty 9 where everything can participate (Servlet 3.1) including the classes themselves, their annotations, and even the other WEB-INF/lib/*.jar files as well.