java - 准备语句错误 : java. sql.SQLException : Parameter index out of range (1 > number of parameters, 这是 0)

Question

我目前在使用这段代码时遇到了一些问题:

 public User validateUser(String username, String password) {

    boolean found = false;
    Connection c = DBHelperClass.getConnection();
    String query = "Select * from user where username= '?' and password= '?' ";


    if (c != null) {
        try {
            PreparedStatement inserter = c.prepareStatement(query);
            inserter.setString(1, username);
            inserter.setString(2, password);
            System.out.println("help: "+query);
            ResultSet resultSet = inserter.executeQuery(query);
            while (resultSet.next()) {
                this.userId = resultSet.getInt("userId");
                this.username = resultSet.getString("usrname");
                this.password = resultSet.getString("password");
                this.address = resultSet.getString("address");
                this.email = resultSet.getString("email");
                this.phone = resultSet.getInt("phone");

                found = true;

            }
        } catch (SQLException ex) {
            Logger.getLogger(User.class.getName()).log(Level.SEVERE, null, ex);
        }

    }
    return this;
}

我得到的错误是:

java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0)

通过阅读其他答案，我尝试改变“？”标记但未能这样做。

Answer 1

改变

 Select * from user where username= '?' and password= '?' 

到

Select * from user where username= ? and password= ?

无需添加'

更新:

并将 inserter.executeQuery(query); 更改为 inserter.executeQuery();