为什么我查的数据在表中不显示。

Question

public class Select_studentnoPanel extends JPanel {
            public Select_studentnoPanel ()
            {
             try{
             jbInit();
             }catch(Exception exception)
             {
             exception.printStackTrace();
             }
            }
            private void jbInit() throws Exception
            {
             this.setLayout(null);
             this.setBackground(new Color(168,233,216));
             button1.setBounds(new Rectangle(314,36,81,23));
             button1.setText("退出");
             button1.addActionListener(new Exit(this));
             label1.setText("学生姓名");
             label1.setBounds(new Rectangle(25,38,71,15));
             button2.setBounds(new Rectangle(246,38,64,23));
             button2.setText("查询");
             button2.addActionListener(new Select_no(this));
             tsno.setBounds(new Rectangle(108,38,126,20));
             list.setBounds(new Rectangle(20,84,442,70));
             this.add(button1);
             this.add(label1);
             this.add(button2);
             this.add(tsno);
             this.add(list);
             this.setVisible(true);
             this.setSize(600,600);

            }
            JButton button1=new JButton();
            JButton button2=new JButton();
            JLabel label1=new JLabel();
            JTextField tsno=new JTextField();
            JList list=new JList();
            public void button1_actionPerformed(ActionEvent e)
            {
             this.setVisible(false);
            }public void button2_actionPerformed(ActionEvent e)
{
String sno=tsno.getText().trim();
GradeManager sm=new GradeManager();
Vector v=sm.findStudent(sno);
list.setListData(v);
}
}
class Select_no implements ActionListener
{
private Select_studentnoPanel adaptee;
Select_no(Select_studentnoPanel adaptee)
{
this.adaptee=adaptee;
}
public void actionPerformed(ActionEvent e)
{
adaptee.button2_actionPerformed(e);
}
}
class  Exit implements ActionListener
{
private Select_studentnoPanel adaptee;
 Exit(Select_studentnoPanel adaptee)
{
this.adaptee=adaptee;
}
public void actionPerformed(ActionEvent e)
{
adaptee.button1_actionPerformed(e);
}
}

Answer 1

你的代码无法运行GradeManager类跑到哪里了？

Answer 2

public class GradeManager {
public int addStudent(Student s)
{

int i=0;
try
{Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");}
catch(ClassNotFoundException ce)
{System.out.println("SQLException:"+ce.getMessage());}
try
{
String url = "jdbc:odbc:class8_10";
String user = "";
String password = "";
Connection con=DriverManager.getConnection(url, user, password);
Statement stmt=con.createStatement();
String sqlstr="insert into student values('"+s.getSno()+"','"+s.getSname()+"','"+s.getSclass()+"','"+s.getSgrade()+"')";
i=stmt.executeUpdate(sqlstr);
stmt.close();
con.close();
}
catch(SQLException e)
{System.out.println("SQLException:"+e.getMessage());}
return i;
}
public int deleteStudent(Student sno)
{
int i=0;
try
{Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");}
catch(ClassNotFoundException ce)
{System.out.println("SQLException:"+ce.getMessage());}
try
{
String url = "jdbc:odbc:class8_10";
String user = "";
String password = "";
Connection con=DriverManager.getConnection(url, user, password);
Statement stmt=con.createStatement();
String sqlstr="delete from student where Sno='"+sno+"'";
i=stmt.executeUpdate(sqlstr);
stmt.close();
con.close();
}
catch(SQLException e)
{System.out.println("SQLException:"+e.getMessage());}
return i;
}
public int updateStudent(String sno,String sname,String sclass,String sgrade)
{
int i=0;
try
{Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");}
catch(ClassNotFoundException ce)
{System.out.println("SQLException:"+ce.getMessage());}
try
{
String url = "jdbc:odbc:class8_10";
String user = "";
String password = "";
Connection con=DriverManager.getConnection(url, user, password);
Statement stmt=con.createStatement();
String sqlstr="update student set sname='"+sname+"',sclass='"+sclass+"','"+sgrade+"'";
i=stmt.executeUpdate(sqlstr);
stmt.close();
con.close();
}
catch(SQLException e)
{System.out.println("SQLException:"+e.getMessage());}
return i;
}
public Vector findStudent(String sno){
Vector s=null;
try
{Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");}
catch(ClassNotFoundException ce)
{System.out.println("SQLException:"+ce.getMessage());}
try
{
String url = "jdbc:odbc:class8_10";
String user = "";
String password = "";
Connection con=DriverManager.getConnection(url, user, password);
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery("select * from student where sno='"+sno+"'");
while(rs.next())
{
System.out.println(
"学号"+rs.getString(1)+"\t"+
"姓名"+rs.getString(2)+"\t"+
"班级 "+rs.getString(3)+"\t"+
"成绩"+rs.getFloat(4)+"\t");
}
stmt.close();
con.close();
}
catch(SQLException e)
{System.out.println("SQLException:"+e.getMessage());}
return s;
}
}