Java 从Jtable更新数据库行：错误

我得到了一个jTable，当应用程序运行时，用数据库项填充它。现在我已经做了一个保存按钮，它修改了更改并将其保存到数据库中，但是我一直得到一个我无法理解的错误

按钮：

private void btnOpslaanActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        int row = jTable1.getSelectedRow();
        int col = jTable1.getSelectedColumn();

        int category_id = (Integer)(jTable1.getValueAt(row, 1));
        String name = jTable1.getValueAt(row, 2).toString();
        double price = (Double)jTable1.getValueAt(row, 3);
        String description = jTable1.getValueAt(row, 4).toString();

        queryManager.updateProductList(category_id, name, price, description);
    }

变量在system out测试时更新（因此工作正常） 我得到一个关于这行的错误：

queryManager.updateProductList(category_id, name, price, description);

queryManager.updateProductList方法：

public void updateProductList(int category_id, String name, double price, String description){
        String sql ="UPDATE product SET categorie_id='" +category_id+ "', naam='" +name+ "', prijs='" +price+ "', omschrijving='"+description+"'";
        ResultSet result = dbmanager.doQuery(sql);
        try {
            result.next();
        } catch (SQLException e) {
            System.out.println("Productlijst updaten is niet gelukt: " + e.getMessage());
        }

    }

希望有人能帮我解决这个问题！还有我得到的错误：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at view.ShowProductList.btnOpslaanActionPerformed(ShowProductList.java:162)
    at view.ShowProductList.access$400(ShowProductList.java:19)
    at view.ShowProductList$6.actionPerformed(ShowProductList.java:108)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
    at java.awt.Component.processMouseEvent(Component.java:6382)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3275)
    at java.awt.Component.processEvent(Component.java:6147)
    at java.awt.Container.processEvent(Container.java:2083)
    at java.awt.Component.dispatchEventImpl(Component.java:4744)
    at java.awt.Container.dispatchEventImpl(Container.java:2141)
    at java.awt.Component.dispatchEvent(Component.java:4572)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4619)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4280)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4210)
    at java.awt.Container.dispatchEventImpl(Container.java:2127)
    at java.awt.Window.dispatchEventImpl(Window.java:2489)
    at java.awt.Component.dispatchEvent(Component.java:4572)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:704)
    at java.awt.EventQueue.access$400(EventQueue.java:82)
    at java.awt.EventQueue$2.run(EventQueue.java:663)
    at java.awt.EventQueue$2.run(EventQueue.java:661)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
    at java.awt.EventQueue$3.run(EventQueue.java:677)
    at java.awt.EventQueue$3.run(EventQueue.java:675)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:674)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

“queryManager”可能没有正确地表示。

---

您试过调试代码吗？

已修复！我需要使用构造函数调用创建一个新的QueryManager对象！谢谢