Java代码错误：参数索引超出范围（1>参数数量，为0）

Question

如果数据库中存在该行，我正在尝试验证用户名和密码。但是我将参数索引超出范围（1>参数数量，即0）。请帮助

Scanner in = new Scanner(System.in);
String password = in .next();
String username = in .next();

PreparedStatement ps = 
                connect.prepareStatement
               ( "select  LastName,BirthDate from employees where LastName= '" + username + "'  and BirthDate = '" + password + "'"  );


            ps.setString (1, username);
            ps.setString (2, password);
            ResultSet rs = ps.executeQuery();

            if (rs.next()) {

                 System.out.println("login completed");
            } else {
                // Quest not completed yet
                 System.out.println("login failed");

                }

Answer 1

您正在将字符串串联与设置准备好的语句参数混合在一起。您应该仅使用两者之一，最好是后者。您的代码应如下所示：

PreparedStatement ps = connect.prepareStatement ( 
    "select LastName,BirthDate from employees where LastName=? and BirthDate=?"
);
ps.setString (1, username);
ps.setString (2, password);
ResultSet rs = ps.executeQuery();