在jsp servlet中我們通常使用Servlet Filter控制用戶是否登入， 是否有權限轉到某個頁面。在struts2中我們應該會想到他的攔截器（Interceptor）， Interceptor在struts2中起著非常重要的作用。 很多struts2中的功能都是使用Interceptor實現的。

需求：簡單的登入界面，讓用戶輸入用戶名、密碼、記住密碼（remember me）。 如果用戶選中remember me的話， 下次就不需要再登入了（使用cookie實現， 用需要點擊logout取消remeber me功能）。 如果用戶起始輸入的地址不是登入頁面的話，在用戶登入之后需要轉到用戶輸入的起始地址。

我們先看看LoginInterceptor.java

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);
		
		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";
					}
					return invocation.invoke();
				}
			}
		}
		setGoingToURL(session, invocation);
		return "login";
	}

	private void setGoingToURL(Map session, ActionInvocation invocation){
		String url = "";
		String namespace = invocation.getProxy().getNamespace();
		if (StringUtils.isNotBlank(namespace) && !namespace.equals("/")){
			url = url + namespace;
		}
		String actionName = invocation.getProxy().getActionName();
		if (StringUtils.isNotBlank(actionName)){
			url = url + "/" + actionName + ".action";
		}
		session.put(GOING_TO_URL_KEY, url);
	}
	
	public UserDAO getUserDao() {
		return userDao;
	}

	public void setUserDao(UserDAO userDao) {
		this.userDao = userDao;
	}

}

首先判斷session中有沒有用戶信息， 如果有的話繼續， 如果沒有的話，檢查cookie中有沒有rememberme的值，如果有的話，用==分割， 取得用戶名密碼進行登入。如果沒有這個用戶的話，記錄下request的action地址然后轉到登入頁面。如果驗證有這個用戶，則繼續下面的interceptor。 如果cookie中沒有信息的話，則記錄request的action地址然后轉到登入頁面。? 以上就是LoginInterceptor的全部代碼。

下面我們看看struts.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts PUBLIC 
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
	<package name="default" extends="struts-default">
		<interceptors>
			<interceptor name="loginInterceptor" class="loginInterceptor"></interceptor>
			<interceptor-stack name="loginDefaultStack">
				<interceptor-ref name="loginInterceptor"></interceptor-ref>
				<interceptor-ref name="defaultStack"></interceptor-ref>
			</interceptor-stack>
		</interceptors>
		<default-interceptor-ref name="loginDefaultStack"></default-interceptor-ref>
		<global-results>
			<result name="login" type="redirect">/login.jsp</result>
		</global-results>		
		<action name="index" class="indexAction">
			<result>/index.jsp</result>
		</action>
		<action name="logout" class="logoutAction"></action>
		
		<action name="login" class="loginAction" method="login">
			<result type="redirect">${goingToURL}</result>
			<result name="input">/login.jsp</result>
			<interceptor-ref name="defaultStack"></interceptor-ref>
		</action>
		
		<action name="register" class="registerAction">
			<result type="redirect">/login.jsp</result>
			<result name="input">/register.jsp</result>
			<interceptor-ref name="defaultStack"></interceptor-ref>
		</action>
	</package>
</struts>

我們是使用的默認的interceptor stack是loginInterceptor， 如果你需要讓不登入的用戶也能訪問的話，你需要配置你的action使用defaultStack。 我們這里的login, register使用的就是defaultStack。 這里要注意的是success的result是我們用LoginInterceptor設過來的值。 這樣我們就能夠轉到用戶輸入的起始頁面。 下面我們再來看看login.jsp 和 loginAction

<%@taglib prefix="s" uri="/struts-tags" %>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	<title>Wallet-Login</title>
</head>
<body>
<h2>Login</h2> 
<s:actionmessage/>
<s:actionerror/>
<s:form action="login" method="post" validate="false" theme="xhtml">
<s:textfield name="loginName" label="Username"></s:textfield><br/>
<s:password name="password" label="Password"></s:password><br/>
<s:checkbox label="Remember Me" name="rememberMe"></s:checkbox>
<s:submit value="%{'Login'}"></s:submit> 
</s:form>
<a href="register.jsp">Register</a>
</body>
</html>

package com.javaeye.dengyin2000.wallet.actions;

import java.util.Map;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;
import org.apache.struts2.interceptor.CookiesAware;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;
import org.apache.struts2.interceptor.SessionAware;

import com.javaeye.dengyin2000.wallet.dao.UserDAO;
import com.javaeye.dengyin2000.wallet.dao.UserNotFoundException;
import com.javaeye.dengyin2000.wallet.domains.User;
import com.javaeye.dengyin2000.wallet.interceptor.LoginInterceptor;
import com.opensymphony.xwork2.ActionSupport;

public class LoginAction extends ActionSupport implements ServletResponseAware, ServletRequestAware, SessionAware, CookiesAware{

	private UserDAO userDao;
	private String loginName;
	private String password;
	private boolean rememberMe;
	private HttpServletResponse response;
	private HttpServletRequest request;
	private Map session;
	private Map cookies;
	private String goingToURL;
	public String getGoingToURL() {
		return goingToURL;
	}
	public void setGoingToURL(String goingToURL) {
		this.goingToURL = goingToURL;
	}
	public boolean isRememberMe() {
		return rememberMe;
	}
	public void setRememberMe(boolean rememberMe) {
		this.rememberMe = rememberMe;
	}
	public String getLoginName() {
		return loginName;
	}
	public void setLoginName(String loginName) {
		this.loginName = loginName;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	
	
	public String login()throws Exception{
		try {
			User user = userDao.attemptLogin(loginName, password);
			if (rememberMe){
				Cookie cookie = new Cookie(LoginInterceptor.COOKIE_REMEMBERME_KEY, user.getLoginName() + "==" + user.getPassword());
				cookie.setMaxAge(60 * 60 * 24 * 14);
				response.addCookie(cookie);
			}
			session.put(LoginInterceptor.USER_SESSION_KEY, user);
			String goingToURL = (String) session.get(LoginInterceptor.GOING_TO_URL_KEY);
			if (StringUtils.isNotBlank(goingToURL)){
				setGoingToURL(goingToURL);
				session.remove(LoginInterceptor.GOING_TO_URL_KEY);
			}else{
				setGoingToURL("index.action");
			}
			return SUCCESS;
		} catch (UserNotFoundException e) {
			addActionMessage("user name or password is not corrected.");
			return INPUT;
		}
	}
	public UserDAO getUserDao() {
		return userDao;
	}
	public void setUserDao(UserDAO userDao) {
		this.userDao = userDao;
	}
	public void setServletResponse(HttpServletResponse response) {
		this.response = response;
	}
	public void setServletRequest(HttpServletRequest request) {
		this.request = request;
	}
	public void setSession(Map session) {
		this.session = session;
	}
	public void setCookiesMap(Map cookies) {
		this.cookies = cookies;
	}
}

差不多就是這么多代碼了。 最后看看logoutAction

package com.javaeye.dengyin2000.wallet.actions;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;

import com.javaeye.dengyin2000.wallet.interceptor.LoginInterceptor;
import com.opensymphony.xwork2.ActionSupport;

public class LogoutAction extends ActionSupport implements ServletRequestAware , ServletResponseAware{

	private HttpServletRequest request;
	private HttpServletResponse response;

	public String execute() throws Exception{
		HttpSession session = request.getSession(false);
		if (session!=null)
			session.removeAttribute(LoginInterceptor.USER_SESSION_KEY);
		
		Cookie[] cookies = request.getCookies();
		if (cookies!=null) {
			for (Cookie cookie : cookies) {
				if (LoginInterceptor.COOKIE_REMEMBERME_KEY.equals(cookie
						.getName())) {
					cookie.setValue("");
					cookie.setMaxAge(0);
					response.addCookie(cookie);
					return "login";
				}
			}
		}
		return "login";
	}

	public void setServletRequest(HttpServletRequest request) {
		this.request = request;
	}

	public void setServletResponse(HttpServletResponse response) {
		this.response = response;
	}

}

這里需要注意的是需要把cookie也清理下。

applicationContext-struts.xml