can we use spring expressions (spel) in other annotations?

Question

I want to be able to do this:

@Controller
@RequestMapping("/#{handlerMappingPaths.security}/*")
public class SecurityController {
  etc

  //for instance, to resuse the value as a base for the folder resolution     
  @Value("#{handlerMappingPaths.security}/")
  public String RESOURCE_FOLDER;

  @RequestMapping(value="/signin-again", method = RequestMethod.GET)
    public String signinAgainHandler() {
        return RESOURCE_FOLDER + "signin_again";
    }
}

this doesn't appear to work now, am I missing something?

Answer 1

One way you can find out things like this is to have a look yourself. This is an example for eclipse, but it should work similarly for other IDEs:

First of all, make sure you have the sources of the spring libraries you are using. This is easiest if you use maven, using the maven-eclipse-plugin or using m2eclipse.

Then, in Eclipse select Navigate -> Open Type.... Enter the type you are looking for (something like RequestMa* should do for lazy typers like myself). Enter / OK. Now right-click the class name in the source file and select References -> Project. In the search view, all uses of this class or annotation will appear.

One of them is DefaultAnnotationHandlerMapping.determineUrlsForHandlerMethods(Class, boolean), where this code snippet will tell you that expression language is not evaluated:

ReflectionUtils.doWithMethods(currentHandlerType, new ReflectionUtils.MethodCallback() {
    public void doWith(Method method) {
        RequestMapping mapping = AnnotationUtils.findAnnotation(
                                     method, RequestMapping.class);
        if (mapping != null) {
            String[] mappedPatterns = mapping.value();
            if (mappedPatterns.length > 0) {
                for (String mappedPattern : mappedPatterns) {
                    // this is where Expression Language would be parsed
                    // but it isn't, as you can see
                    if (!hasTypeLevelMapping && !mappedPattern.startsWith("/")) {
                        mappedPattern = "/" + mappedPattern;
                    }
                    addUrlsForPath(urls, mappedPattern);
                }
            }
            else if (hasTypeLevelMapping) {
                urls.add(null);
            }
        }
    }
}, ReflectionUtils.USER_DECLARED_METHODS);

Remember, it's called Open Source. There's no point in using Open Source Software if you don't try to understand what you are using.