filter实现登录验证，并实现页面跳转到登录前浏览的页面（同步异步皆可）

框架使用SSH

1、首先写好filter，如下

package com.alpha.web.filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class CheckLoginFilter implements Filter {
	private String redirectURL = "";
	private List notCheckURLList = null;

	@Override
	public void destroy() {
		this.notCheckURLList.clear();
	}

	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
			FilterChain filterChain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest)servletRequest;
		HttpServletResponse response = (HttpServletResponse)servletResponse;
		HttpSession session= request.getSession();
		
		/**
		 * loginKey为用户登录成功后写到session中的，在这里通过获取loginKey判断是否登录成功
		 * 如果登录成功，则跳转到登录前浏览的页面，如果登录前是从login.jsp过来的，则不跳转
		 */
		Object loginKey = session.getAttribute("loginKey");
		if(loginKey != null && loginKey.toString().equals("success")) {
			session.removeAttribute("loginKey");
			Object uri = session.getAttribute("requestURI");
			if(uri != null) {
				response.sendRedirect(uri.toString());
				return;
			}
		}
		/**
		 * 判断是否是不需要执行过滤的页面，如果是则直接放行
		 */
		String requestURI = request.getRequestURI();
		for(String url : this.notCheckURLList){
			if(requestURI.indexOf(url) != -1) {
				filterChain.doFilter(request, response);
				return;
			}
		}
		
		/**
		 * 如果用户未登录，记录目前访问的页面，并跳转到登录页面
		 */
		if(session.getAttribute("user") == null) {
			if(requestURI.endsWith("jsp"))
				session.setAttribute("requestURI", requestURI);
			response.sendRedirect(request.getContextPath() + "/" + redirectURL);
			return;
		} 
		filterChain.doFilter(request, response);
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		//初始化配置的参数
		redirectURL = filterConfig.getInitParameter("redirectURL");
		String notCheckURLStr = filterConfig.getInitParameter("notCheckURLList");
		if(notCheckURLStr != null) {
			notCheckURLList = new ArrayList();
			notCheckURLList.clear();
			String[] urls = notCheckURLStr.split(",");
			for (String url : urls) {
				notCheckURLList.add(url);
			}
		}
	}

}

2、接下来在web.xml中配置filter，如下

	
	
		checkLoginFilter
		com.alpha.web.filter.CheckLoginFilter
		
			检查失败后需要定向到的页面
			redirectURL
			Login/Login.jsp
		
		
			不用检查用户的页面列表，用","分隔
			notCheckURLList
			Login.jsp,login.action
		
	
	
		checkLoginFilter
		*.jsp
	
	
	
		checkLoginFilter
		*.action
	
	
	
	
	
		struts2
		
			org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
		
	
	
		struts2
		/action/*
	

注意：要将filter的配置放在struts配置前面，否则filter将过滤不到action

3、用户验证的action，这里简单写下思路

//这是刚开始写的action，打算在action处理时直接跳转，若为同步请求，直接由jsp中的form请求过来，可以直接在action中跳转成功，后来发现ajax请求时根本跳不过去

public void login(){

	User user = validateUser(username,password);

	if(user != null) {
		request.getSession().setAttribute("user",user);

		Object obj =  request.getSession().getAttribute("requestURI");
		if(obj != null) {
   		try {
			response.sendRedirect(obj.toString());
	    		return;
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
}

//以下是不分同步异步的，通过在session中添加标记的方式，然后在filter中判断是否登录成功

	public void login() {	
		User user = userManagerService.validate(username, password);
		if(user != null){
			this.session.put("user", user);
			this.session.put("loginKey", "success");
		}else{
			message = "用户名或密码错误！";
		}
		//通过json方式和客户端交互的代码，可以写在下面		
	}