Jquery+Servlet+JDBC实现登录注册功能

以下是一个简化的例子，展示了如何使用jQuery、Servlet和JDBC来实现登录和注册功能。

前端代码（HTML + jQuery）

<!-- 登录表单 -->
<form id="loginForm">
  <input type="text" name="username" placeholder="Username">
  <input type="password" name="password" placeholder="Password">
  <button type="submit">Login</button>
</form>
 
<!-- 注册表单 -->
<form id="registerForm">
  <input type="text" name="username" placeholder="Username">
  <input type="password" name="password" placeholder="Password">
  <button type="submit">Register</button>
</form>
 
<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<script>
$(document).ready(function(){
  // 登录提交
  $('#loginForm').submit(function(e){
    e.preventDefault();
    $.post('LoginServlet', $(this).serialize(), function(data){
      alert(data);
    });
  });
 
  // 注册提交
  $('#registerForm').submit(function(e){
    e.preventDefault();
    $.post('RegisterServlet', $(this).serialize(), function(data){
      alert(data);
    });
  });
});
</script>

后端代码（Servlet + JDBC）

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
 
// 登录Servlet
public class LoginServlet extends HttpServlet {
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
 
    try {
      Class.forName("com.mysql.cj.jdbc.Driver");
      Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password");
      PreparedStatement stmt = con.prepareStatement("SELECT * FROM users WHERE username=? AND password=?");
 
      stmt.setString(1, username);
      stmt.setString(2, password);
 
      ResultSet rs = stmt.executeQuery();
      if (rs.next()) {
        response.getWriter().println("Login successful");
      } else {
        response.getWriter().println("Login failed");
      }
 
      rs.close();
      stmt.close();
      con.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}
 
// 注册Servlet
public class RegisterServlet extends HttpServlet {
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("usern