We recently upgraded Jetty from v7.6.8 to v9.1.3. This introduced a 404 not found HTTP error when accessing the root of any UI.
The problem is that the existing code attaches two handlers to the root, one of which is a handler for static resources. In Jetty 9.1.3, we are no longer allowed to do this. Instead, we are supposed to use ResourceHandler rather than ServletContextHandler for serving static resources: http://stackoverflow.com/questions/10284584/serving-static-files-w-embedded-jetty.