Question

我的项目需要帮助..........此代码显示了＆＃39;结果集关闭后不允许操作＆＃39;单击按钮时出现错误消息....................请帮助....谢谢

private void jButton20ActionPerformed(java.awt.event.ActionEvent evt) {                                          
    String car_id = "";
    Date rent_date = null;
    Date return_date = null;
    Date rented_date = null;

    String model = "";
    String rent_place = "";
    String return_place = "";
    double disrent = 0.0;
    double fine = 0.0;
    double rent = 0.0;
    double totrent = 0.0;
    int mem_id = Integer.parseInt(memidget.getText());


    try {

        Class.forName("java.sql.DriverManager");
        Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/lion", "root", "achinth");
        Statement stmt = (Statement) con.createStatement();
        String query = "select * from car_use_log where returned='N' and mem_id=" + mem_id + " ;";
        ResultSet rs = stmt.executeQuery(query);
        int a = 0;

        while (rs.next()) {
            car_id = rs.getString("car_id");
            rent_date = rs.getDate("rent_date");
            return_date = rs.getDate("return_date");
            rented_date = rs.getDate("rented_date");
            model = rs.getString("model");
            rent_place = rs.getString("place_of_rent");
            return_place = rs.getString("place_of_return");
            a++;
        }


        if (a == 0) {
            JOptionPane.showMessageDialog(this, "You have currently not rented a car");
        } else {
            curstatus.setVisible(true);
            mem_login.setVisible(false);
            t18.setText(model);
            t19.setText(car_id);
            t20.setText("" + rent_date);
            t63.setText("" + rented_date);
            t21.setText("" + return_date);
            t24.setText(rent_place);
            t25.setText(return_place);

            String query1 = "select rent from car_details where model='" + model + "';";
            ResultSet rs1 = stmt.executeQuery(query1);
            while (rs1.next()) {
                rent = rs1.getDouble("rent");
            }
            int no_days = 0;
            Date curdate = null;//to initalise
            int totno_days = 0;
            int return_cur_diff = 0;
            if (rented_date != null) {

                String query2 = "select datediff('" + return_date + "',curdate()),datediff(curdate(),'" + rented_date + "'),datediff('" + return_date + "','" + rented_date + "'),curdate();";
                ResultSet rs2 = stmt.executeQuery(query2);


                while (rs2.next()) {
                    no_days = rs2.getInt(2);
                    curdate = rs2.getDate(4);
                    return_cur_diff = rs.getInt(1);
                }


                if (return_cur_diff < 0) {  //Car is not returned after return date ....... fine calulation needed
                    disrent = totno_days * rent;
                    fine = -2 * return_cur_diff * rent;
                    totrent = fine + disrent;
                }
                else if (return_cur_diff > 0) {
                    disrent = no_days * rent;
                    jLabel39.setText("Rent to be Paid on Return Date :");
                    totrent = disrent;
                }
                else  {
                    disrent = totno_days * rent;
                    totrent = disrent;
                }

            }
            }
            t22.setText("" + disrent);
            t23.setText("" + fine);
            t26.setText("" + totrent);




    } catch (Exception e) {
        JOptionPane.showMessageDialog(this, e.getMessage());
    }

}

Answer 1

实际上，问题在于：

if (rented_date != null) {

                String query2 = "select datediff('" + return_date + "',curdate()),datediff(curdate(),'" + rented_date + "'),datediff('" + return_date + "','" + rented_date + "'),curdate();";
                ResultSet rs2 = stmt.executeQuery(query2);


                while (rs2.next()) {
                    no_days = rs2.getInt(2);
                    curdate = rs2.getDate(4);
                    return_cur_diff = rs.getInt(1);
                }

来自Oracle文档（http://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html）：

当Statement对象时，ResultSet对象自动关闭生成它的是关闭，重新执行或用于检索下一个由多个结果序列产生。

您正在重用导致关闭stmt对象的rs对象;但是在重用while对象后，它在stmt循环中使用。顺便说一句，我认为这只是一个错字。

结果集关闭后不允许操作 - 错误

1 个答案: