這篇文章主要爲大家詳細介紹了java實現登錄案例的相關代碼，具有一定的參考價值，感興趣的小夥伴們可以參考一下
本文實例爲大家分享了java實現登錄案例的具體代碼，供大家參考，具體內容如下
一、環境搭建
JDK1.8 + Tomcat1.8
二、目錄結構
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 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 {
// 設置編碼格式
response.setContentType("text/html;charset=utf-8");// setContentType設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域對象的數據 String loginName =
* (String)request.getAttribute("loginName",userName);
*
*/
/**
* 在用戶主頁，判斷session對象不爲空且存在指定的屬性則登錄成功 才能訪問資源。從session域對象中取出會話數據
*
*
* */
// 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 session唯一標識ID 則登錄不成功，跳轉到登錄頁面
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
* 設置編碼格式
* 根據參數名獲取參數值
* 判斷邏輯（使用session域對象）
*
*
*/
public class LoginServlet extends HttpServlet {
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// 設置編碼格式
request.setCharacterEncoding("utf-8");// setCharacterEncoding設置服務器的編碼格式
// 1.根據參數名獲取參數值
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：
* context域對象：不合適，可能會覆蓋數據
* request.setAttribute("loginName",userName);
*
* request域對象：不合適，整個網站必須得使用轉發技術來跳轉
* request.getRequestDispatcher("/IndexServlet").forward(request,response);
*
* session域對象：合適
* response.sendRedirect(request.getContextPath()+"/IndexServlet")
* */
//2.1 登錄成功
// 2.1.1創建session對象 用於保存數據
HttpSession session = request.getSession();
// 2.1.1把數據保存到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
知道了如何實現前端頁面與後端的數據交互
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麼？
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持神馬文庫。