java使用Filter实现自动登录的方法

package com.learning.web.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.learning.domain.User;
import com.learning.service.UserService;

@WebServlet("/servlet/loginServlet")
public class LoginServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  String username = request.getParameter("username");
  String password = request.getParameter("password");
  String autologin = request.getParameter("autologin");
  
  UserService userService=new UserService();
  User user = userService.findUser(username, password);
  //user不为null，则登录成功
  if (user!=null) {
  //创建cookie来保存用户信息
  Cookie cookie=new Cookie("user", user.getUsername()+"&"+user.getPassword());
  cookie.setPath("/");
  //autologin不为null，则记住了登录状态
  if (autologin!=null) {
   cookie.setMaxAge(1*60*60*24);//一天的有效时间
  }
  else {
   cookie.setMaxAge(0);
  }
  response.addCookie(cookie);
  request.getSession().setAttribute("user", user);
  request.getRequestDispatcher("/home.jsp").forward(request, response);
  }else {
  response.sendRedirect(request.getContextPath()+"/homeLogin.jsp");
  }
  
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 doGet(request, response);
 }

}

package com.learning.web.filter;

import java.io.IOException;

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.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.jstl.core.Config;

import com.learning.domain.User;
import com.learning.service.UserService;

@WebFilter(urlPatterns="/*",initParams={@WebInitParam(name="autologin",value="login"),@WebInitParam(name="",value="")})
public class AutoFilter implements Filter{

 private FilterConfig filterConfig;
 @Override
 public void destroy() {
 }

 @Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
  throws IOException, ServletException {
 // 转换对象
 HttpServletRequest httpServletRequest = (HttpServletRequest) request;
 HttpServletResponse httpServletResponse = (HttpServletResponse) response;
 // 获得访问的路径
 String uri = httpServletRequest.getRequestURI();
 String contextPath = httpServletRequest.getContextPath();
 uri = uri.substring(contextPath.length() + 1);
 // 获得初始化参数
 String login = filterConfig.getInitParameter("autologin");
 System.out.println("直接通行的路径："+login);
 // 不包含"login"的路径就要进行过滤 （xxxlogin.jsp 不需要自动登录）
 if (!uri.contains(login)) {
  HttpSession session = httpServletRequest.getSession();
  User u = (User) session.getAttribute("user");
  if (u != null) {
  System.out.println("session不为null");
  chain.doFilter(request, response);
  } else {

  // 处理业务逻辑
  // 1.获得cookie 得到User的信息

  String username = "";
  String password = "";
  UserService userService = new UserService();
  Cookie[] cookies = httpServletRequest.getCookies();
  for (int i = 0;cookies!=null&& i < cookies.length; i++) { 
   if ("user".equals(cookies[i].getName())) {
   String string = cookies[i].getValue();
   String[] values = string.split("&");
   username = values[0];
   password = values[1];
   User user = userService.findUser(username, password);
   
   // 不为空则放入session
   if (user != null) {
    System.out.println("自动登录了");
    httpServletRequest.getSession().setAttribute("user", user);
   }
   }
  }
  }
 }
 // 2.放行
 chain.doFilter(request, response);
 }


 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
 
 this.filterConfig=filterConfig;
 
 }

}