jsp用户登录代码

JSP（JavaServer Pages）是一种用于创建动态Web内容的技术，它允许开发者在HTML页面中嵌入Java代码。下面是一个简单的JSP用户登录代码示例，包括前端表单和后端验证逻辑。

前端表单 (login.jsp)

<!DOCTYPE html>
<html>
<head>
    <title>Login Page</title>
</head>
<body>
    <h2>Login</h2>
    <form action="authenticate.jsp" method="post">
        Username: <input type="text" name="username"><br><br>
        Password: <input type="password" name="password"><br><br>
        <input type="submit" value="Login">
    </form>
</body>
</html>

后端验证 (authenticate.jsp)

<%@ page import="java.sql.*" %>
<%
    String username = request.getParameter("username");
    String password = request.getParameter("password");

    // 假设数据库连接信息
    String url = "jdbc:mysql://localhost:3306/mydatabase";
    String dbUsername = "dbuser";
    String dbPassword = "dbpass";

    try {
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn = DriverManager.getConnection(url, dbUsername, dbPassword);
        String sql = "SELECT * FROM users WHERE username = ? AND password = ?";
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setString(1, username);
        pstmt.setString(2, password);
        ResultSet rs = pstmt.executeQuery();

        if (rs.next()) {
            // 登录成功
            session.setAttribute("username", username);
            response.sendRedirect("welcome.jsp");
        } else {
            // 登录失败
            out.println("Invalid login credentials. <a href='login.jsp'>Try again</a>");
        }
        rs.close();
        pstmt.close();
        conn.close();
    } catch (Exception e) {
        out.println("Error: " + e.getMessage());
    }
%>