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重新措辞这个问题，因为它不是很清楚。我的问题是，每当 generateReport 方法尝试使用 model.getColumnCount() 时，它都会返回零并给出 ResultSet is Closed 错误。

但是，如果我删除该 finally 块，一切都会按预期工作。如何通过关闭连接正确执行此操作？

我是否认为该模型仅存在于我使用过的 createTable 方法中

model = new ResultSetTableModel(rs);

即使我将模型声明为类变量？

创建 JTable 的方法

private void createTable() {                                         

databaseName = (txtQueryDatabase.getText());
String sql = txtQueryString.getText();
openDatabase();

try {
    ResultSet rs = stmt.executeQuery(sql);
    model = new ResultSetTableModel(rs);
    tblEmployee.setModel(model);
    txtQueryCount.setText(Integer.toString(model.getRowCount()));
} catch (SQLException e) {
    errorMessage(e);
} catch (Exception e) {
    errorMessage(e);
} finally {
    closeDatabase();
}

写入文件的方法

private void generateReport(File file) throws IOException {
    file.createNewFile();
    BufferedWriter bfw = new BufferedWriter(new FileWriter(file));

    for (int i = 0; i < model.getColumnCount(); i++) {
        bfw.write(model.getColumnName(i));
        bfw.write(" | ");
    }
    for (int i = 0; i < model.getRowCount(); i++) {
        bfw.newLine();
        for (int j = 0; j < model.getColumnCount(); j++) {
            bfw.write(model.getValueAt(i, j).toString());
            bfw.write(" | ");
        }
    }
    bfw.close();
}

ResultSetTableModel 类

    public ResultSetTableModel(ResultSet aResultSet) {
    try {
        rs = aResultSet;
        rsmd = rs.getMetaData();
        data = new ArrayList<Object>();
        while (rs.next()) {
            Object[] row = new Object[rsmd.getColumnCount()];
            for (int i = 0; i < row.length; i++) {
                row[i] = rs.getObject(i + 1);
            }
            data.add(row);
        }
    } catch (SQLException e) {
        message.errorMessage(e);
    }
}

@Override
public Object getValueAt(int row, int col) {
    if (row < data.size()) {
        return ((Object[]) data.get(row))[col];
    } else {
        return null;
    }
}

@Override
public int getRowCount() {
    return data.size();
}

@Override
public String getColumnName(int count) {
    try {
        return rsmd.getColumnName(++count);
    } catch (SQLException e) {
        message.errorMessage(e);
        return "";
    }
}

@Override
public int getColumnCount() {

    try {
        return rsmd.getColumnCount();
    } catch (SQLException e) {
        message.errorMessage(e);
        return 0;
    }
}

}

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