java如何实现登录

<!DOCTYPE html> <html> <head> <title>faill.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8">  </head> <body> <font color='red' size='3'>亲，你的用户名或密码输入有误！请重新输入!</font> <br /> <a href="/project03/login.html" >返回登录页面</a> </body> </html>

<!DOCTYPE html> <html> <head> <title>Login.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="this is my page"> <meta http-equiv="content-type" content="text/html; charset=UTF-8">  </head> <body> <form action="/project03/LoginServlet" method="post"> 用户名：<input type="text" name="UserName" /><br /> 密    码：<input type="password" name="UserPwd" /><br /> <input type="submit" value="登录" /> </form> </body> </html>

package cn.itcase.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * 用户主页逻辑 * */ public class IndexServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 设置编码格式 response.setContentType("text/html;charset=utf-8");// setContentType设置浏览器的编码格式 // 1.信息输出至浏览器 PrintWriter writer = response.getWriter(); String html = ""; /** * 接收request域对象的数据 String loginName = * (String)request.getAttribute("loginName",userName); * */ /** * 在用户主页，判断session对象不为空且存在指定的属性则登录成功才能访问资源。从session域对象中取出会话数据 * * * */ // 2.得到session对象 HttpSession session = request.getSession(false); // 2.1如果不存在session对象，登录不成功，跳转到登录页面 if (session == null) { response.sendRedirect(request.getContextPath() + "/Login.html"); return; } // 2.2没有在session对象域中找到相应 session唯一标识ID 则登录不成功，跳转到登录页面 String loginName = (String) session.getAttribute("loginName"); if (loginName == null) { response.sendRedirect(request.getContextPath() + "/Login.html"); return; } html = "<html><body>欢迎回来，" + loginName + "，<a href='" + request.getContextPath() + "/LogoutServlet'>安全退出</a></body></html>"; writer.write(html); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }

package cn.itcase.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; /** * 登录的逻辑 * 设置编码格式 * 根据参数名获取参数值 * 判断逻辑（使用session域对象） * * */ public class LoginServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 设置编码格式 request.setCharacterEncoding("utf-8");// setCharacterEncoding设置服务器的编码格式 // 1.根据参数名获取参数值 String userName = request.getParameter("UserName"); String userPwd = request.getParameter("UserPwd"); // 2.登录是否的逻辑判断 if("eric".equals(userName) && "123456".equals(userPwd)){ /**分析使用技术： * context域对象：不合适，可能会覆盖数据 * request.setAttribute("loginName",userName); * * request域对象：不合适，整个网站必须得使用转发技术来跳转 * request.getRequestDispatcher("/IndexServlet").forward(request,response); * * session域对象：合适 * response.sendRedirect(request.getContextPath()+"/IndexServlet") * */ //2.1 登录成功 // 2.1.1创建session对象用于保存数据 HttpSession session = request.getSession(); // 2.1.1把数据保存到session域中 session.setAttribute("loginName", userName); // session对象的唯一标识"loginName" 唯一标识名称 userName //session.setMaxInactiveInterval(1*60*60*24*30); // session对象的有效时长可以配置全局的有效时长 //2.1.3跳转到用户主页 response.sendRedirect(request.getContextPath() + "/IndexServlet"); //sendRedirect()重定向 getContextPath()请求路径 }else{ //2.2登录失败请求重定向 response.sendRedirect(request.getContextPath() + "/fail.html"); } } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setCharacterEncoding("utf-8"); doGet(request,response); } }

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