Using interceptors (Interceptor) to control logins and permissions in Struts2

using interceptors (Interceptor) to control logins and permissions in Struts2
In a JSP servlet, we typically use servlet filter to control whether a user is logged in or not, and has permission to go to a page. In Struts2 we should think of his interceptor (interceptor), interceptor plays a very important role in STRUTS2. Many of the features in STRUTS2 are implemented using interceptor.

Requirement: Simple login interface, let user enter user name, password, remember password (remember me). If the user selects remember me, the next time you do not need to log in (using the cookie implementation, with the need to click Logout Cancel the Remeber me function). If the user entered the address is not the login page, after the user login needs to go to the user input start address.

Let's see Logininterceptor.java first.
Java code    package com.javaeye.dengyin2000.wallet.interceptor;      import  java.util.map;      import javax.servlet.http.cookie;   import  javax.servlet.http.httpservletrequest;      import org.apache.commons.lang.stringutils;    import org.apache.struts2.strutsstatics;      import  com.javaeye.dengyin2000.wallet.dao.userdao;   import  com.javaeye.dengyin2000.wallet.dao.usernotfoundexception;   import  com.javaeye.dengyin2000.wallet.domains.user;   import com.opensymphony.xwork2.actioncontext;    import com.opensymphony.xwork2.actioninvocation;   import  com.opensymphony.xwork2.interceptor.abstractinterceptor;      public class  logininterceptor extends abstractinterceptor {       public  static final string user_session_key= "Wallet.session.user";       public  static final string cookie_rememberme_key= "Wallet.cookie.rememberme";        public static final string going_to_url_key= "GOING_TO";               private UserDAO userDao;            @Override        public string intercept ( actioninvocation invocation)  throws Exception {                       actioncontext actioncontext  = invocation.getinvocationcontext ();            httpservletrequest request=  (HttpServletRequest)  actioncontext.get (StrutsStatics.HTTP_REQUEST);    &NBsp;                  map  session = actioncontext.getsession ();            if  (Session != null && session.get (user_session_key)  != null) {               return  Invocation.invoke ();           }                       Cookie[]  Cookies = request.getcookies ();           if  ( Cookies!=null)  {               for   (cookie cookie : cookies)  {                    if  (Cookie_rememberme_key.equals (Cookie.getname ()))  {                         string value = cookie.getvalue ();                        if  (Stringutils.isnotblank ( Value))  {                            string[] split = value.split ("= =");                             String userName = split[0];                             string password = split[1];                            try  {                                User user =  userdao                                         .attemptlogin (Username, password);                                 session.put (user_session_key, user);                            } catch  ( Usernotfoundexception e)  {                                 Setgoingtourl (session, invocation);                                 return  "Login";                            }                        } else  {                             setgoingtourl (session, invocation);                             return  "Login";