Spring AOP pass argument of a controller method

I have a controller as follows

@Controller
@RequestMapping(value = "/")
public class HomeController {
    @RequestMapping("/")
    public String home(Map<String,Object> map) {
        map.put("val2","val2");
        return "mainpage"; //it is the jsp file name
    }
}

Now In my aspect class method I want to put another value in this map variable defined in the controller method

@Aspect
public class UserInfo {
    @Before("execution(* org.controller.HomeController(..)) ")
    public void m1(){
        //Map<String,Object> map
        // get the map here and add
        map.put("val1","val1);
    }
}

so that when i call this map form mainpage.jsp file I get both value as

${val1}
${val2}

How can I do this???