当用户没有登录，直接访问servlet容器时，就会跳转到登陆页面去让用户登录。（还可以用filter过滤器进行统一过滤，那种方法很简单，建议使用过滤器拦截吗，见访问页面时，判断用户是否登录，若没有登录，将跳转到登录页面（二））
1.登录页面login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <!-- 请求转发 --> <% String authority = (String)request.getAttribute("authority"); %> <% out.print(authority); %> <form action="UserLoginServlet" method="post"> username:<input type="text" value="<%=null == request.getAttribute("username")?"" : request.getAttribute("username") %>" name="username"><br> password:<input type="text" name="password"><br> authority:<select name="authority"> <option value="1" <%="1".equals(authority)?"selected = selected" : "" %>>common user</option> <option value="2" <%="2".equals(authority)?"selected = selected" : "" %>>adminstrator</option> </select> <br> <input type="submit"> </form> <!-- 重定向 -->> <%String error = request.getParameter("error"); String authority1 = request.getParameter("authority"); %> <form action="UserLoginServlet" method="post"> username:<input type="text" value="<%=null == request.getParameter("username")?"" : request.getParameter("username") %>" name="username"><br> password:<input type="text" name="password"><br> authority:<select name="authority"> <option value="1" <%="1".equals(authority1)?"selected = selected" : "" %>>common user</option> <option value="2" <%="2".equals(authority1)?"selected = selected" : "" %>>adminstrator</option> </select> <br> <input type="submit"> </form> </body> </html>
2.web.xml文件配置
<!-- session 实例 start--> <servlet> <servlet-name>UserLoginServlet</servlet-name> <servlet-class>com.servlet.UserLoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UserLoginServlet</servlet-name> <url-pattern>/session/UserLoginServlet</url-pattern> </servlet-mapping> <servlet> <servlet-name>QueryServlet</servlet-name> <servlet-class>com.servlet.QueryServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>QueryServlet</servlet-name> <url-pattern>/session/QueryServlet</url-pattern> </servlet-mapping> <!-- session 实例 end-->
3.servlet（com.servlet.LoginServlet）
package com.servlet; import java.io.IOException; import java.io.PrintWriter; import java.util.ArrayList; import java.util.List; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String username = req.getParameter("username"); String password = req.getParameter("password"); String repassword = req.getParameter("repassword"); int age = Integer.parseInt(req.getParameter("age")); String result = ""; if(age > 18) { result = "success"; } else { result += "age <= 18"; } if(!password.equals(repassword)) { result += "password != repassword"; } req.setAttribute("username", username); req.setAttribute("age", age); //c重定向 resp.sendRedirect("result.jsp"); //转发 // RequestDispatcher rd = req.getRequestDispatcher("result.jsp"); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }
4.主页面(index.jsp)
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ page import="com.javabean.User" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <a href="QueryServlet">query</a><br> <% User user = (User)session.getAttribute("user"); if(null == user) { response.sendRedirect("login.jsp"); } if("2".equals(((User)session.getAttribute("user")).getAuthority())){ %> <a href="UpdateServlet">update</a> <%} %> </body> </html>
5.QueryServlelt.java
package com.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; import com.javabean.User; public class QueryServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { HttpSession session = req.getSession(); if(null == session.getAttribute("user")) { resp.sendRedirect("login.jsp"); return ; } User user = (User)session.getAttribute("user"); if("1".equals(user.getAuthority()))//表示普通用户 { System.out.println("sihbai"); }else { System.out.println("chenggong"); } } }
6.UpdateServlet.java
package com.servlet; import java.io.IOException; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.javabean.User; public class UserLoginServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String username = (String)req.getParameter("username"); String password = (String)req.getParameter("password"); String authority = (String)req.getParameter("authority"); if("1".equals(authority)) { //登录的是普通用户 if("zhangsan".equals(username) && "123".equals(password)) { //将用户的信息放置到session中 User user = new User(); user.setUsername(username); user.setPassword(password); user.setAuthority(authority); HttpSession session = req.getSession(); session.setAttribute("user", user); req.getRequestDispatcher("index.jsp").forward(req, resp); return; } } else if("2".equals(authority)) { //登录的是系统管理员 if("lisi".equals(username) && "456".equals(password)) { //将用户的信息放置到session中 User user = new User(); user.setUsername(username); user.setPassword(password); user.setAuthority(authority); HttpSession session = req.getSession(); session.setAttribute("user", user); req.getRequestDispatcher("index.jsp").forward(req, resp); return; } } //表示登录失败 System.out.println("shibai"); //请求转发模式 // req.setAttribute("username", username); // req.setAttribute("authority",authority); // RequestDispatcher rd = req.getRequestDispatcher("login.jsp"); // rd.forward(req, resp); //重定向 resp.sendRedirect("login.jsp?error=true&username="+username+"&authority="+authority); } }