My web.xml highlights several classes as not assignable to javax.servlet.Filter or javax.servlet.Servlet. See the first image as an example. However, these classes are actually implementations of the respective Filter and Servlet interfaces. You can see this in the second image. The only special thing I can note about these classes is that they are provided by a jar library which is in another module on which this module depends. The impact is high because is obscures other, potentially more serious errors.