为什么结果显示failed to connect to database,问号处具体该填什么

Question

  public UserInfoManager(){
        try{
            // 连接MySQL数据库
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/userdb?useSSL=false";
            Connection connection = DriverManager.getConnection(url, "root", "password");
            // 预处理SQL语句
            loginStatement = connection.prepareStatement("SELECT * FROM users WHERE username=? AND password=?");
            updateStatement = connection.prepareStatement("UPDATE users SET email=?, phone=? WHERE username=?");
            passwordStatement = connection.prepareStatement("UPDATE users SET password=? WHERE username=user1 AND password=?");
            registerStatement = connection.prepareStatement("INSERT INTO users (username, password, email, phone) VALUES (?, ?, ?, ?)");

为什么结果显示failed to connect to database,问号处具体该填什么

Answer 1

?是参数占位，与连接数据库失败没有关系。本机安装MySQL并启动没？
设置参数可参考这个：https://blog.csdn.net/m0_61961937/article/details/126931897