用戶(hù)的登錄和注銷(xiāo)是最常見(jiàn)的Web應(yīng)用案例，當(dāng)一個(gè)應(yīng)用的客戶(hù)登錄了以后，其他所有的會(huì)話(huà)都得知道這個(gè)用戶(hù)已經(jīng)登錄還很有可能得提取用戶(hù)的昵稱(chēng)予以顯示等等，所以，只有把登錄成功的用戶(hù)的信息放入到Session中才能夠辦到使所有的Servlet都能訪(fǎng)問(wèn)到用戶(hù)的登錄狀態(tài)，
第一是登錄的界面，是HTML的一個(gè)表單，非常的簡(jiǎn)單<!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>登陸界面</title></head><body><form action="/Web/servlet/LoginServlet" method="post">帳號(hào):<input type="text" name="username"><br>密碼:<input type="passWord" name="password"><br><input type="submit" value="登錄"></form></body></html>第二是處理登錄信息的LoginServlet
package com.bird.login; import java.io.IOException; import java.io.PRintWriter; import java.util.ArrayList; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { /** * @category 使用Session處理用戶(hù)登陸 * @author Bird */ private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String username = request.getParameter("username"); String password = request.getParameter("password"); List<User> list = Db.getAll(); for(User u: list){ if(u.getUsername().equals(username) && u.getPassword().equals(password)){ request.getSession().setAttribute("user", u);//登錄成功，將用戶(hù)數(shù)據(jù)放入到Session中 response.sendRedirect("/Web/index.jsp"); return;//進(jìn)行重定向，并且下面的代碼不再執(zhí)行 } } out.write("您的應(yīng)戶(hù)名或密碼錯(cuò)誤"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } } class Db{ public static List<User> list = new ArrayList<User>(); static{ list.add(new User("aaa","123")); list.add(new User("bbb","123")); list.add(new User("ccc","123")); } public static List<User> getAll(){ return list; } }
這里有個(gè)小疑問(wèn)，如果用戶(hù)是在數(shù)據(jù)庫(kù)中中，是把用戶(hù)全部讀出來(lái)再遍歷快？還是直接在JDBC是查詢(xún)來(lái)的快
第三，用戶(hù)的信息封裝在User對(duì)象中package com.bird.login;/*** @category 封裝用戶(hù)的數(shù)據(jù)的對(duì)象* @author Bird**/public class User {private String username;private String password;public User() {}public User(String username, String password) {this.username = username;this.password = password;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}}第四是處理用戶(hù)注銷(xiāo)的Servletpackage com.bird.login; 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; public class LoginOutServlet extends HttpServlet { /** * @category 退出登錄的Servlet,注銷(xiāo) * @author Bird */ private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(false);//防止創(chuàng)建Session if(session == null){ response.sendRedirect("/Web/index.jsp"); return; } session.removeAttribute("user"); response.sendRedirect("/Web/index.jsp"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } } 第五是最終的顯示界面%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>My JSP 'index.jsp' starting page</title></head><body>歡迎您，${user.username} <br><a href="/Web/servlet/LoginOutServlet">退出登錄</a></body></html>新聞熱點(diǎn)
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