It seems that Navigation (cmd+6) cannot detect @RequestMapping-annotated methods when the URL is defined as a constant instead of a literal string.
For example:

public class MyPaths {
    public static final String RESOURCE_PATH = "/somepath/resource";
}
@Controller
public class MyController {
    @RequestMapping(MyPaths.RESOURCE_PATH)
    public String method() {
        ... 
    }
}

In STS4, if I press Ctrl+6 (I'm using Eclipse-based STS4 on Linux) and start typing something like "@/some", the results list does not include the mapping for "/somepath/resource".

It would be nice if STS4 implemented such detection.