java實現(xiàn)登錄案例

更新時間：2019年08月22日 14:26:52 作者：以何問心

這篇文章主要為大家詳細介紹了java實現(xiàn)登錄案例的相關(guān)代碼，文中示例代碼介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們可以參考一下

本文實例為大家分享了java實現(xiàn)登錄案例的具體代碼，供大家參考，具體內(nèi)容如下

一、環(huán)境搭建

JDK1.8 + Tomcat1.8

二、目錄結(jié)構(gòu)

三、代碼示例

3.1、fail.html頁面

<!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">
 
<!--<link rel="stylesheet" type="text/css" href="./styles.css" rel="external nofollow" rel="external nofollow" >-->
 
</head>
 
<body>
 <font color='red' size='3'>親， 你的用戶名或密碼輸入有誤！請重新輸入!</font>
 <br />
 <a href="/project03/login.html" >返回登錄頁面</a>
</body>
</html>

3.2、Login.htm頁面

<!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">
<!--<link rel="stylesheet" type="text/css" href="./styles.css" >-->
</head>
<body>
 <form action="/project03/LoginServlet" method="post">
 用戶名：<input type="text" name="UserName" /><br />
 密&nbsp;&nbsp;&nbsp;&nbsp;碼：<input type="password" name="UserPwd" /><br />
 <input type="submit" value="登錄" />
 </form>
</body>
</html>

3.3、IndexServlet.java

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;
 
/**
 * 用戶主頁邏輯
 * */
public class IndexServlet extends HttpServlet {
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 
 // 設(shè)置編碼格式 
 response.setContentType("text/html;charset=utf-8");// setContentType設(shè)置瀏覽器的編碼格式
 
 // 1.信息輸出至瀏覽器
 PrintWriter writer = response.getWriter();
 String html = "";
 
 /**
 * 接收request域?qū)ο蟮臄?shù)據(jù) String loginName =
 * (String)request.getAttribute("loginName",userName);
 * 
 */
 
 /**
 * 在用戶主頁，判斷session對象不為空且存在指定的屬性則登錄成功 才能訪問資源。從session域?qū)ο笾腥〕鰰挃?shù)據(jù)
 * 
 * 
 * */
 // 2.得到session對象
 HttpSession session = request.getSession(false);
 // 2.1如果不存在session對象，登錄不成功，跳轉(zhuǎn)到登錄頁面
 if (session == null) {
 response.sendRedirect(request.getContextPath()
 + "/Login.html");
 return;
 }
 // 2.2沒有在session對象域中找到相應(yīng) session唯一標識ID 則登錄不成功，跳轉(zhuǎn)到登錄頁面
 String loginName = (String) session.getAttribute("loginName");
 if (loginName == null) {
 response.sendRedirect(request.getContextPath() + "/Login.html");
 return;
 }
 html = "<html><body>歡迎回來，" + 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);
 }
 
}

3.4、LoginServlet.java

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;
/**
 * 登錄的邏輯
 * 設(shè)置編碼格式
 * 根據(jù)參數(shù)名獲取參數(shù)值
 * 判斷邏輯（使用session域?qū)ο螅?
 * 
 * 
 */
public class LoginServlet extends HttpServlet {
 protected void doGet(HttpServletRequest request,
 HttpServletResponse response) throws ServletException, IOException {
 // 設(shè)置編碼格式
 request.setCharacterEncoding("utf-8");// setCharacterEncoding設(shè)置服務(wù)器的編碼格式
 
 // 1.根據(jù)參數(shù)名獲取參數(shù)值
 String userName = request.getParameter("UserName");
 String userPwd = request.getParameter("UserPwd");
 
 // 2.登錄是否的邏輯判斷
 if("eric".equals(userName) && "123456".equals(userPwd)){
 /**分析使用技術(shù)：
 * context域?qū)ο螅翰缓线m，可能會覆蓋數(shù)據(jù)
 * request.setAttribute("loginName",userName);
 * 
 * request域?qū)ο螅翰缓线m，整個網(wǎng)站必須得使用轉(zhuǎn)發(fā)技術(shù)來跳轉(zhuǎn)
 * request.getRequestDispatcher("/IndexServlet").forward(request,response);
 * 
 * session域?qū)ο螅汉线m
 * response.sendRedirect(request.getContextPath()+"/IndexServlet")
 * */
 //2.1 登錄成功
 // 2.1.1創(chuàng)建session對象 用于保存數(shù)據(jù)
 HttpSession session = request.getSession();
 
 // 2.1.1把數(shù)據(jù)保存到session域中
 session.setAttribute("loginName", userName); // session對象的唯一標識"loginName" 唯一標識名稱 userName
 //session.setMaxInactiveInterval(1*60*60*24*30); // session對象的有效時長 可以配置全局的有效時長
 
 //2.1.3跳轉(zhuǎn)到用戶主頁
 response.sendRedirect(request.getContextPath() + "/IndexServlet"); //sendRedirect()重定向 getContextPath()請求路徑
 }else{
 //2.2登錄失敗 請求重定向
 response.sendRedirect(request.getContextPath() + "/fail.html");
 }
 }
 
 protected void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 response.setCharacterEncoding("utf-8");
 doGet(request,response);
 }
 
}

3.5、LogoutServlet.java

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;
 /**
 * 退出邏輯
 * */
public class LogoutServlet extends HttpServlet {
 
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 /**
 * 安全退出
 * 刪除session對象中指定的loginName屬性即可
 * 
 */
 HttpSession session = request.getSession(false);
 if(session != null){
 session.removeAttribute("loginName");
 }
 //返回登錄頁面
 response.sendRedirect(request.getContextPath() + "/Login.html");
 }
 
 
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 doGet(request,response);
 
 
 }
 
}

3.6、總結(jié)

知道了如何實現(xiàn)前端頁面與后端的數(shù)據(jù)交互

疑惑：如果有多個用戶難道還一個一個的去判斷他存不存在么？

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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