在mysql数据库

Question

我正在尝试将一个数据从我的jinternal框架插入到mysql数据库中。我正在使用结果集类方法进行插入。即使变量不为null，我总是会得到NullPointerException。我无法确定我的代码中出现此null异常的位置。这是我的jbutton的actionListener片段：

public void actionPerformed(ActionEvent e) {
    String action = e.getActionCommand();
    String fabric = txtFabric.getText();
    String supplier = txtSupplier.getText();

    if(action.equals("Add")){
        btnAdd.setText("Save");
        btnAdd.setActionCommand("Save");
        txtFabric.setEnabled(true);
        txtFabric.grabFocus();
        txtSupplier.setEnabled(true);
        txtFabric.setText("");
        txtSupplier.setText("");
    }
    else if(action.contentEquals("Save")){
        if(fabric.isEmpty() || supplier.isEmpty()){
            System.out.println("Nothing to save");
        }
        else{
            System.out.println(fabric+" "+supplier);
            try {
                model.addFabric(fabric, supplier); // the error points to this line
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        }

        btnAdd.setText("Add");
        btnAdd.setActionCommand("Add");
        txtFabric.setEnabled(false);
        txtSupplier.setEnabled(false);
        tableModel.fireTableDataChanged();
    }
}

这是我的类方法插入的片段：

public void addFabric(String item,String supplier) throws SQLException
{
    try{
        sql = "INSERT INTO fabric(ItemDesc,Supplier) values(?,?)";
        pstmt = con.prepareStatement(sql);
        pstmt.setString(1, item);
        pstmt.setString(2, supplier);
        pstmt.executeUpdate();
    }
    catch(Exception ex){
        ex.printStackTrace();
    }finally{
        pstmt.close();
        con.close();
    }
}

以下是我指向插入行的例外情况：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at main.Fabric.actionPerformed(Fabric.java:148)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)