Instead of using a compare editor you can enable quick diff support and see the changes within the text editor. This feature can be enabled via the General > Editors > Text Editors > Quick Diff preference page:
Because you are using Spring MVC, which has no connection whatsoever to JAX-RS, which @QueryParam is for. Spring using @RequestParam. If you are going to use Spring, I suggest you get rid of your JAX-RS Dependency, so you don't get confused on what you can and can't use.