【4-1】使用JSP+JDBC完成一个用户登录程序，登录成功后可以使用session进行用户的登录验证，用户根据需要也可以直接进行登录的退出操作

工程目录结构

数据表

直接生成数据库与表的sql文件下载

demo0401 下载

工程文件下载

38.实验四-JSP基础程序设计-第一题下载

代码

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%@ page import="java.sql.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录</title>
</head>
<%!public static final String dbDriver = "com.mysql.cj.jdbc.Driver";
    public static final String dbUrl = "jdbc:mysql://localhost:3306/demo0401?useSSL=false&serverTimezone=UTC";
    public static final String dbUser = "root";
    public static final String dbPass = "";%>
<%
    Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
%>
<%
    Class.forName(dbDriver); // 加载驱动程序
conn = DriverManager.getConnection(dbUrl, dbUser, dbPass); //连接
//String sql = "select * from user where";
//pstmt = conn.prepareStatement(sql);
//rs = pstmt.executeQuery();
%>
<%
    //判断是否有登陆凭证
if (session.getAttribute("username") != null) {
%>
<jsp:forward page="success.jsp" />
<%
    }
%>
<%
    String username = request.getParameter("username");
String password = request.getParameter("password");
if (!(username == null || "".equals(username) || password == null || "".equals(password))) {
    String sql = "select * from user where username=? and password=?";
    pstmt = conn.prepareStatement(sql);
    pstmt.setString(1, username);
    pstmt.setString(2, password);
    rs = pstmt.executeQuery();
    if (rs.next()) {
        session.setAttribute("username", username);
%>
<jsp:forward page="success.jsp" />
<%
    }
}
%>
<body>
	<form action="login.jsp" method="post">
		用户名: <input type="text" name="username"><br /> 密码：<input
			type="password" name="password"><br /> <input type="submit"
			value="登录"><input type="reset" value="重置">
	</form>
</body>
</html>

success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>成功页面</title>
</head>
<body>
	登录成功
	<br /> 你好，<%=session.getAttribute("username")%>
	<a href="logout.jsp">退出登录</a>
</body>
</html>

logout.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>注销</title>
</head>
<body>
<%
session.invalidate();
response.setHeader("refresh", "0;url=login.jsp");
%>

</body>
</html>

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