jfinal interceptor初试

public class LoginInterceptor implements Interceptor {    @Override    public void intercept(Invocation inv) {        String username=inv.getController().getSessionAttr("username");        System.out.println(username);        inv.getController();        if(username==null||username.equals("")){            inv.getController().redirect("/loginpage");        }else{            inv.invoke();        }    }}