code: @Path("/users/{user.login}/musics/{music.id}")
      @Put
  	public void addToMyList(User user, Music music) {
      	User currentUser = userInfo.getUser();
  	    userDao.refresh(currentUser);
  	    
  	    validator.check(user.getLogin().equals(currentUser.getLogin()), 
  	            new SimpleMessage("user", "you_cant_add_to_others_list"));
  
  	    validator.check(!currentUser.getMusics().contains(music), 
  	            new SimpleMessage("music", "you_already_have_this_music"));
  
  		validator.onErrorUsePageOf(UsersController.class).home();
  
  		music = musicDao.load(music);
  		currentUser.add(music);
  		
  		result.redirectTo(UsersController.class).home();
  	}
docs: Accepts HTTP PUT requests. <br>
  
  <strong>URL:</strong> /users/login/musics/id (for example,
  /users/john/musics/3 adds the music with id 3 to the john's
  collection)<br>
  
  <strong>View:</strong> redirects to user's home <br>
  
  You can use more than one variable on URI. Since the browsers
  don't support PUT method you have to pass an additional parameter:
  <strong>_method=PUT</strong> for calling this method.<br>
  
  This method adds a music to a user's collection.