java j2se基础类进不去了，只能在这个栏里问了~（关于连接数据库，并查询的问题）

Question

import java.sql.*;
import javax.swing.*;import java.awt.*;
import java.awt.event.*;
public class ShanChu extends JFrame 
{
   private static final int WIDTH=258;
   private static final int HEIGHT=150;
   JButton shanChu;
       public static void main(String args[])
       {
        ShanChu a=new ShanChu();
        a.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        a.show();
       }
       
       public ShanChu()
       {        
       Container con=getContentPane();
       Toolkit kit=this.getToolkit();
       Dimension screenSize=kit.getScreenSize();
       Image image=kit.getImage("image/9.jpg");
       setIconImage(image);
       int width=screenSize.width;
       int height=screenSize.height;
       int x=(width-WIDTH)/2;
       int y=(height-HEIGHT)/2;
       setLocation(x,y);
       this.setSize(WIDTH,HEIGHT);
       setResizable(false);
       shanChu=new JButton("点击->删除");
       ShanChuPanel aaa=new ShanChuPanel();       
       add(aaa,BorderLayout.CENTER);
       //shanChu.setSize(10,5);
       add(shanChu,BorderLayout.SOUTH);
       
       
       } class ShanChuPanel extends JPanel implements ActionListener
 {
  
 
  JLabel qing;
  JTextField xueHaoT;
      public ShanChuPanel()
      {
       qing=new JLabel("请输入您要删除学生记录的学生学号~");
       xueHaoT=new JTextField("",15);       
       add(qing);
       add(xueHaoT);
       
       shanChu.addActionListener(this);
      }
 public void actionPerformed(ActionEvent event)
 {
 
LianJie lianJie=new LianJie();
Connection con=lianJie.getCon();
try
{
Statement sta=con.createStatement();
    String xh=xueHaoT.getText();

   if(xh.equals(""))
  JOptionPane.showMessageDialog(null,"请输入学号！！","错误！",
         JOptionPane.WARNING_MESSAGE,new ImageIcon("image/2.jpg"));
   else
   {
  int i=0;
  ResultSet rs=sta.executeQuery("select * from xs");
  while(rs.next())
  {  

  String XH=rs.getString("学号");
  if(xh.equals(XH))
  {
  String bb="delete from xs where 学号 ='" + xh + "'";
  System.out.println("aaaaaaaa");
   sta.executeUpdate(bb);
  System.out.println("bbbbbbbb");
  i=1;
  }

  }
if(i==0)
JOptionPane.showMessageDialog(null,"没有该项记录！","错误！",
         JOptionPane.WARNING_MESSAGE,new ImageIcon("image/8.jpg"));
   }
}
catch(Exception e)
{
e.printStackTrace();
 JOptionPane.showMessageDialog(null,"数据库操作失败","错误！",
          JOptionPane.WARNING_MESSAGE,new ImageIcon("image/2.jpg"));
}

 }
   
 }
}我用的是eclipse做的，在删除一个记录时，不知道为什么老是弹出对话筐来显示我定义的“数据库操作失败”，其中“aaaaaaaa”和“bbbbbbbbb”也显示出来了（我要删除的那个数据也成功删除），可为什么还有错误呢？错误提示是：java.sql.SQLException: ResultSet is closed
at sun.jdbc.odbc.JdbcOdbcResultSet.checkOpen(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcResultSet.next(Unknown Source)
at ShanChu$ShanChuPanel.actionPerformed(ShanChu.java:75)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$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.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(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)
请大哥们给找找原因

Answer 1

ResultSet rs=sta.executeQuery("select * from xs");while(rs.next())
{ .....
  System.out.println("aaaaaaaa");
  
  sta.executeUpdate(bb); //问题出在这里，当找到要删除的记录时，就把它删了，下次再while(rs.next())是，就不是原来的sta了。这个地方应该另外搞一个Statement
  System.out.println("bbbbbbbb");
  .....
}~~~~~~~~~~~~~~~~~~~~~~~~~~~`
删除记录之前，不用先查询，直接删即可。

Answer 2

ResultSet rs=sta.executeQuery("select * from xs");
                   while(rs.next())    
                   {  
                   XH=rs.getString("学号");            
                     if(xh.equals(XH))  
                     {                        
                    try
                    {                  
                    zy=(String)zhuanYeT.getSelectedItem(); 
                        String sb="update xs set 姓名='" + xm + "',性别='" + xb + "',学分='" + xf + "',专业='" + zy + "',备注='" + bz + "',出生时间='" + rq + "' where 学号=xh";
                        System.out.println("bbbbbbb");
                           sta.executeUpdate(sb);
                           System.out.println("aaaaaaa");
                       JOptionPane.showMessageDialog(null,"数据修改成功！！","成功！",
                        JOptionPane.WARNING_MESSAGE,new ImageIcon("image/2.jpg"));
                       a=1;
                       break;
                    }
                    catch(Exception e)
                    {
                    JOptionPane.showMessageDialog(null,"数据修改时出现错误！！！"
                    ,"错误！",JOptionPane.WARNING_MESSAGE,new ImageIcon("image/1.jpg"));  
                    }
                    
                     }                     
                   }
这个呢，这个只运行到输出“bbbbbbb”没有输出“aaaaaa”这个怎么个改？

Answer 3

......"' where 学号=xh";~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
删除记录、修改记录，为什么要先查询呢？服务器不够忙？时间多得用不完？

Answer 4

上一贴不是已经告诉你了吗？
......"' where 学号=xh;   -->  ......"' where 学号='" + xh + "'"

Answer 5

还有记住，update是也要再搞一个Statement，不然还出delete时的现象。