实现用户自动登陆
思路是这样的：
1、在用户登陆成功后，发送一个名称为user的cookie给客户端，cookie的值为用户名和md5加密后的密码。
2、编写一个AutoLoginFilter，这个filter检查用户是否带有名称为user的cookie来，如果有，则调用dao查询cookie的用户名和密码是否和数据库匹配，匹配则向session中存入user对象（即用户登陆标记），以实现程序完成自动登陆。
核心代码如下：
处理用户登录的控制器：LoginServlet
1 package me.gacl.web.controller; 2 3 import java.io.IOException; 4 5 import javax.servlet.ServletException; 6 import javax.servlet.http.Cookie; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse; 10 11 import me.gacl.dao.UserDao; 12 import me.gacl.domain.User; 13 import me.gacl.util.WebUtils; 14 15 public class LoginServlet extends HttpServlet { 16 17 public void doGet(HttpServletRequest request, HttpServletResponse response) 18 throws ServletException, IOException { 19 20 String username = request.getParameter("username"); 21 String password = request.getParameter("password"); 22 23 UserDao dao = new UserDao(); 24 User user = dao.find(username, password); 25 if(user==null){ 26 request.setAttribute("message", "用户名或密码不对！！"); 27 request.getRequestDispatcher("/message.jsp").forward(request, response); 28 return; 29 } 30 request.getSession().setAttribute("user", user); 31 //发送自动登陆cookie给客户端浏览器进行存储 32 sendAutoLoginCookie(request,response,user); 33 request.getRequestDispatcher("/index.jsp").forward(request, response); 34 } 35 36 /** 37 * @Method: sendAutoLoginCookie 38 * @Description: 发送自动登录cookie给客户端浏览器 39 * @Anthor:孤傲苍狼 40 * 41 * @param request 42 * @param response 43 * @param user 44 */ 45 private void sendAutoLoginCookie(HttpServletRequest request, HttpServletResponse response, User user) { 46 if (request.getParameter("logintime")!=null) { 47 int logintime = Integer.parseInt(request.getParameter("logintime")); 48 //创建cookie,cookie的名字是autologin，值是用户登录的用户名和密码，用户名和密码之间使用.进行分割，密码经过md5加密处理 49 Cookie cookie = new Cookie("autologin",user.getUsername() + "." + WebUtils.md5(user.getPassword())); 50 //设置cookie的有效期 51 cookie.setMaxAge(logintime); 52 //设置cookie的有效路径 53 cookie.setPath(request.getContextPath()); 54 //将cookie写入到客户端浏览器 55 response.addCookie(cookie); 56 } 57 } 58 59 public void doPost(HttpServletRequest request, HttpServletResponse response) 60 throws ServletException, IOException { 61 62 doGet(request, response); 63 } 64 65 }
处理用户自动登录的过滤器：AutoLoginFilter
1 package me.gacl.web.filter; 2 3 import java.io.IOException; 4 5 import javax.servlet.Filter; 6 import javax.servlet.FilterChain; 7 import javax.servlet.FilterConfig; 8 import javax.servlet.ServletException; 9 import javax.servlet.ServletRequest; 10 import javax.servlet.ServletResponse; 11 import javax.servlet.http.Cookie; 12 import javax.servlet.http.HttpServletRequest; 13 import javax.servlet.http.HttpServletResponse; 14 15 import me.gacl.dao.UserDao; 16 import me.gacl.domain.User; 17 import me.gacl.util.WebUtils; 18 19 public class AutoLoginFilter implements Filter { 20 21 public void doFilter(ServletRequest req, ServletResponse resp, 22 FilterChain chain) throws IOException, ServletException { 23 24 HttpServletRequest request = (HttpServletRequest) req; 25 HttpServletResponse response = (HttpServletResponse) resp; 26 //如果已经登录了，就直接chain.doFilter(request, response)放行 27 if(request.getSession().getAttribute("user")!=null){ 28 chain.doFilter(request, response); 29 return; 30 } 31 32 //1.得到用户带过来的authlogin的cookie 33 String value = null; 34 Cookie cookies[] = request.getCookies(); 35 for(int i=0;cookies!=null && i<cookies.length;i++){ 36 if(cookies[i].getName().equals("autologin")){ 37 value = cookies[i].getValue(); 38 } 39 } 40 41 //2.得到 cookie中的用户名和密码 42 if(value!=null){ 43 String username = value.split("\\.")[0]; 44 String password = value.split("\\.")[1]; 45 46 //3.调用dao获取用户对应的密码 47 UserDao dao = new UserDao(); 48 User user = dao.find(username); 49 String dbpassword = user.getPassword(); 50 51 //4.检查用户带过来的md5的密码和数据库中的密码是否匹配,如匹配则自动登陆 52 if(password.equals(WebUtils.md5(dbpassword))){ 53 request.getSession().setAttribute("user", user); 54 } 55 } 56 57 chain.doFilter(request, response); 58 } 59 60 public void destroy() { 61 62 } 63 64 public void init(FilterConfig filterConfig) throws ServletException { 65 66 } 67 }
如果想取消自动登录，那么可以在用户注销时删除自动登录cookie，核心代码如下：
1 package me.gacl.web.controller; 2 3 import java.io.IOException; 4 5 import javax.servlet.ServletException; 6 import javax.servlet.http.Cookie; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse; 10 11 public class CancelAutoLoginServlet extends HttpServlet { 12 13 public void doGet(HttpServletRequest request, HttpServletResponse response) 14 throws ServletException, IOException { 15 //移除存储在session中的user 16 request.getSession().removeAttribute("user"); 17 //移除自动登录的cookie 18 removeAutoLoginCookie(request,response); 19 //注销用户后跳转到登录页面 20 request.getRequestDispatcher("/login.jsp").forward(request, response); 21 } 22 23 /** 24 * @Method: removeAutoLoginCookie 25 * @Description: 删除自动登录cookie， 26 * JavaWeb中删除cookie的方式就是新创建一个cookie，新创建的cookie与要删除的cookie同名， 27 * 设置新创建的cookie的cookie的有效期设置为0，有效路径与要删除的cookie的有效路径相同 28 * @Anthor:孤傲苍狼 29 * 30 * @param request 31 * @param response 32 */ 33 private void removeAutoLoginCookie(HttpServletRequest request, HttpServletResponse response) { 34 //创建一个名字为autologin的cookie 35 Cookie cookie = new Cookie("autologin",""); 36 //将cookie的有效期设置为0，命令浏览器删除该cookie 37 cookie.setMaxAge(0); 38 //设置要删除的cookie的path 39 cookie.setPath(request.getContextPath()); 40 response.addCookie(cookie); 41 } 42 43 public void doPost(HttpServletRequest request, HttpServletResponse response) 44 throws ServletException, IOException { 45 doGet(request, response); 46 } 47 }