Question

我想从DefaultTableModel创建ResultSet。为此，我需要Object[][]。

为此，我必须在遍历表格之前指定对象的size：我转到rs.last()，然后转到rs.getRow()，然后转到rs.beforeFirst(); 之后，rs.next()不会在while周期内执行。我做错了什么？

public static DefaultTableModel buildTableModel(ResultSet _resultSet) {
    ResultSetMetaData metaData;
    Object[] columnNames = null;
    Object[][] tableData = null;
    int columnCount;
    int currentRowNumber = 0;

    try {
        metaData = _resultSet.getMetaData();
        columnCount = metaData.getColumnCount();
        columnNames = new Object[columnCount];

        _resultSet.last();
        tableData = new Object[_resultSet.getRow()][columnCount];
        _resultSet.beforeFirst();

        for (int currentColumn = 0; currentColumn <= columnCount; currentColumn++) {
            columnNames[currentColumn] = metaData.getColumnName(currentColumn + 1);
        }

        while (_resultSet.next()) {
            for (int columnIndex = 0; columnIndex <= columnCount; columnIndex++) {
                tableData[currentRowNumber][columnIndex] = _resultSet.getObject(columnIndex + 1);
            }

            currentRowNumber++;
        }
    } catch (SQLException ex) {
        System.out.println("bad");
    }

    return new DefaultTableModel(tableData, columnNames);

}

Answer 1

可能您的ResultSet不是滚动不敏感的，也就是说，它只能向前遍历。
请参阅文档here：

[...]默认的ResultSet对象不可更新，并且只有一个向前移动的游标。因此，您只能迭代一次，并且只能从第一行到最后一行。 [...]

要创建双向，请执行以下操作：

Connection conn = DriverManager.getConnection(...);
Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ...);
ResultSet rset = stmt.executeQuery(sql);

Answer 2

首先，您需要从ResultSetMetaData打印列名称。比你申请_resultSet.last();和_resultSet.beforeFirst();。这样它就一直在我的机器上工作。

public static DefaultTableModel buildTableModel(ResultSet _resultSet) {
    ResultSetMetaData metaData;
    Object[] columnNames = null;
    Object[][] tableData = null;
    int columnCount;
    int currentRowNumber = 0;

    try {
        metaData = _resultSet.getMetaData();
        columnCount = metaData.getColumnCount();
        columnNames = new Object[columnCount];
        // Print column here.
        for (int currentColumn = 0; currentColumn <= columnCount; currentColumn++) {
            columnNames[currentColumn] = metaData.getColumnName(currentColumn + 1);
        }
        tableData = new Object[_resultSet.getRow()][columnCount];

        //Here point resultSet cursor to last and beforeFirst.
        _resultSet.last();

        _resultSet.beforeFirst();

        // After swaping the above part. Now it will enter on while loop.
        while (_resultSet.next()) {
            for (int columnIndex = 0; columnIndex <= columnCount; columnIndex++) {
                tableData[currentRowNumber][columnIndex] = _resultSet.getObject(columnIndex + 1);
            }

            currentRowNumber++;
        }
    } catch (SQLException ex) {
        System.out.println("bad");
    }

    return new DefaultTableModel(tableData, columnNames);

}

在Java中忽略ResultSet.beforeFirst（）

2 个答案: