servlet无法连接MySQL数据库

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;

@WebServlet("/servlet-example")
public class ServletExample extends HttpServlet {
    private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String USERNAME = "username";
    private static final String PASSWORD = "password";

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Connection conn = null;
        Statement stmt = null;
        try {
            // 加载驱动程序
            Class.forName(JDBC_DRIVER);

            // 建立数据库连接
            conn = DriverManager.getConnection(DB_URL, USERNAME, PASSWORD);

            // 创建执行SQL语句的Statement对象
            stmt = conn.createStatement();

            // 执行SQL语句
            String sql = "SELECT * FROM mytable";
            ResultSet rs = stmt.executeQuery(sql);

            // 处理查询结果
            while (rs.next()) {
                // 获取结果集中的数据
                String name = rs.getString("name");
                int age = rs.getInt("age");
                // 在此处进行处理或响应
            }

            // 关闭结果集、Statement和数据库连接
            rs.close();
            stmt.close();
            conn.close();
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                // 关闭数据库连接
                if (stmt != null)
                    stmt.close();
                if (conn != null)
                    conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}