Question

我目前在使用此代码时遇到一些问题：

 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：参数索引超出范围（1＆gt;数参数，即0）

从阅读其他答案我尝试改变'？'标签但未能这样做。

Answer 1

更改

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

到

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

无需添加'

<强>更新：

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

Answer 2

java.sql.SQLException：参数索引超出范围（1＆gt;数参数，即0）

您收到此错误是因为您拨打了executeQuery(query)而不是executeQuery()，因此它认为您的查询不需要任何参数，但您提供的不止一个导致此异常，因此只需使用inserter.executeQuery()。

已经提到的第二个错误是，您不需要在查询中使用引号，它应该只是Select * from user where username= ? and password= ?

Answer 3

错误消息表示查询中的参数为零。这是因为你使用撇号转义了问号字符。在不使用问号的撇号的情况下重写查询。

String query = "Select * from user where username= ? and password= ?";

Answer 4

感谢帮助人员，这是固定代码：

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();
            while (resultSet.next()) {
                this.userId = resultSet.getInt("userId");
                this.username = resultSet.getString("username");
                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;
}

我需要改变的一切就是删除＆＃39;＆＃39;在附近？并将executeQuery（query）更改为executeQuery（）

万分感谢！

准备语句错误：java.sql.SQLException：参数索引超出范围（1＆gt;参数个数，为0）

4 个答案: