Question

我在Java eclipse中有一条错误消息。我在MySql中有一个数据库，它有colomns String user_name，int id_time，int id_desk，int user_password。我希望使用

获得一行的列数据

public ArrayList showReservation（String user_name）抛出SQLException {

    // array list keeps the information
    ArrayList<String> showReservation = new ArrayList<String>();
    try{

        String getReservationSql = "SELECT * FROM reservation " 
                +"WHERE user_name ='" + user_name + "';";
        rs = stmt.executeQuery(getReservationSql);

        // first element of the array list keeps user name
        showReservation.add("" + rs.getString("user_name")); 

        // second element of the array list keeps id of the desk which is selected by user
        showReservation.add("" + rs.getInt("id_time")); 

        // third element of the array list keeps id of the time interval which is selected by user
        showReservation.add("" + rs.getInt("id_desk"));  

        // forth element of the array list keeps user's password which is generated automatically in a controller class
        showReservation.add("" + rs.getInt("user_password")); 

    }catch (SQLException ex) {
        System.out.println("Error: " + ex.getMessage());
    }
    return showReservation;
}

但是当我运行此代码时，我收到一个错误：在开始结果集之前。我该如何解决这个错误？谢谢

Answer 1

您永远不会前进到ResultSet中的第一个结果。使用the next() method前进到下一条记录，当没有更多记录时返回false。

rs = stmt.executeQuery(getReservationSql);
while (rs.next())
{
   // Make your calls to getString and getInt here
}

Answer 2

在尝试调用任何ResultSet getter方法之前使用next

rs = stmt.executeQuery(getReservationSql);
if (rs.next()) {
   ...
}

除此之外：考虑Using Prepared Statements

JDBC错误：在开始结果集之前

2 个答案: