尝试获取MySQL表

Question

我有一个由4个字符串和2个整数组成的简单表（其中一个是ID）。

我使用一个特殊函数来获取该表中的所有行：

public Booking[] displayAllBookings() throws ClassNotFoundException, SQLException{
    Connection con = connect.getConnection();

    PreparedStatement counter = (PreparedStatement) con.prepareStatement("select count(*) from bookings");
    ResultSet count = counter.executeQuery();

    Booking[] array = new Booking[count.getInt(1)]; 

    String name = null,surname = null,begindate = null,enddate = null;
    int persons = 0,i=0;

    PreparedStatement posted = (PreparedStatement) con.prepareStatement("SELECT * FROM bookings");
    result = posted.executeQuery();
    while (result.next()){
        begindate = result.getString("begindate");
        enddate = result.getString("enddate");
        name = result.getString("Name");
        surname = result.getString("Surname");
        persons = result.getInt("persons");
        Booking temp =  new Booking(begindate,enddate,name,surname,persons);
        array[i++]=temp;
    }
    return array;
}

但是当我执行它时，我得到了这个例外：

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:897)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:886)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:790)
at com.mysql.jdbc.ResultSetImpl.getInt(ResultSetImpl.java:2472)
at DataBase.DataCommunicatorBooking.displayAllBookings(DataCommunicatorBooking.java:59)
at DataBase.main.displayAll(main.java:125)
at DataBase.main.main(main.java:71)

我已经尝试查找此异常，但找不到与我的问题相对应的任何内容。

Answer 1

您正在尝试获取 maxPersons 列的值，该列甚至未在表格中定义...您肯定是 人员

 name = result.getString("Name");
 maxPersons = result.getInt("persons");
 Room temp =  new Room(name,maxPersons);

Answer 2

问题在于

PreparedStatement counter = (PreparedStatement) con.prepareStatement("select count(*) from bookings");
ResultSet count = counter.executeQuery();

所以我使用ArrayList就像这样：

public Booking[] displayAllBookings() throws ClassNotFoundException, SQLException{
        Connection con = connect.getConnection();

        ArrayList<Booking> bookings = new ArrayList<Booking>(); 

        String name = null,surname = null,begindate = null,enddate = null;
        int persons = 0,i=0;

        PreparedStatement posted = (PreparedStatement) con.prepareStatement("SELECT * FROM bookings");
        result = posted.executeQuery();
        while (result.next()){
            begindate = result.getString("begindate");
            enddate = result.getString("enddate");
            name = result.getString("Name");
            surname = result.getString("Surname");
            persons = result.getInt("persons");
            Booking temp =  new Booking(begindate,enddate,name,surname,persons);
            bookings.add(temp);
        }
        return bookings.toArray(new Booking[bookings.size()]);
    }

这解决了问题;

Answer 3

这是因为“maxPersons”栏不存在，你可能会选择“人”