初学者：我做了一个jdbc的程序但是报错，不知道该怎样解决，请大家看看，说说为什么和怎么解决

Question

不好意思错误报告写错了，应该时：
jdataframe.java:123: unreported exception java.lang.ClassNotFoundException; must
 be caught or declared to be thrown
                                Class.forName(driver);
                                             ^
jdataframe.java:124: unreported exception java.sql.SQLException; must be caught
or declared to be thrown
                                Connection cn1=DriverManager.getConnection(url,"
sa","");
                                                                          ^
jdataframe.java:125: unreported exception java.sql.SQLException; must be caught
or declared to be thrown
                                Statement stmt1=cn1.createStatement();
                                                                   ^
jdataframe.java:128: unreported exception java.sql.SQLException; must be caught
or declared to be thrown
                                stmt1.executeUpdate(SQL1);
                                                   ^
jdataframe.java:129: unreported exception java.sql.SQLException; must be caught
or declared to be thrown
                                cn1.close();
                                         ^

Answer 1

加一个try catch 要捕获异常
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.sql.*;public class JDataFrame extends JFrame {
    
    /**
     * The constructor.
     */ 
     static String driver="com.microsoft.jdbc.sqlserver.SQLServerDriver"; 
     static String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=northwind";
     JTextField txtComName=null;
     JTextField txtAdr=null;
     JTextField txtCity=null;
     String strId=null;     public JDataFrame() {
JLabel labcomname=new JLabel();  
        labcomname.setSize(40,4);
        JLabel labadr=new JLabel();
        labadr.setSize(40,4);
        JLabel labcity=new JLabel();
        labcity.setSize(40,4);
        txtComName=new JTextField(20);
        txtComName.setSize(20,4);
        txtAdr=new JTextField(20);
        txtAdr.setSize(40,4);
        txtCity=new JTextField(20);
        txtCity.setSize(40,4);
        Container container=this.getContentPane();
        JPanel selPanel=new JPanel();
        selPanel.setLayout(new FlowLayout());
        selPanel.add(labcomname);
        selPanel.add(labadr);
        selPanel.add(labcity);
        selPanel.setSize(200,100);
        JPanel updatePanel=new JPanel();
        updatePanel.setLayout(new FlowLayout());
        updatePanel.add(txtComName);
        updatePanel.add(txtAdr);
        updatePanel.add(txtCity);
        updatePanel.setSize(200,100);
        JButton butOK=new JButton("OK");
        butOK.setSize(20,4);
        
        Container myFrm=this.getContentPane();
        myFrm.setLayout(new BorderLayout());
        myFrm.add(selPanel,BorderLayout.WEST);
        myFrm.add(updatePanel,BorderLayout.EAST);
        myFrm.add(butOK,BorderLayout.SOUTH);
        
        //read database
       
        try
        {
        Class.forName(driver);
    
        Connection cn=DriverManager.getConnection(url,"sa","");
        String SQL="Select CompanyName,Address,City From Customers";
        Statement stmt=cn.createStatement();
        ResultSet rs=stmt.executeQuery(SQL);
        if (rs.next())
        {
         labcomname.setText(rs.getString("CompanyName"));
         labadr.setText(rs.getString("Address"));
         labcity.setText(rs.getString("city"));
         strId=rs.getString("CustomerID");
        }
        rs.close();
        cn.close();
         }
         catch (Exception e)      
         {
           JOptionPane.showMessageDialog(null,e.getMessage());
         }
        this.setSize(400,240);
        this.setVisible(true);
       // container.setLayout(new BorderLayout());
        
     butOK.addActionListener(
     new ActionListener(){
     public void actionPerformed(ActionEvent event)
     {try{
    
     Class.forName(driver);
     Connection cn1=DriverManager.getConnection(url,"sa","");
     Statement stmt1=cn1.createStatement();
     String SQL1="Update Customers Set CompanyName='" + txtComName.getText() + "',Address='"
     + txtAdr.getText() + "',city='" + txtCity.getText() + "' Where CustomerID='" + strId + "'";
     stmt1.executeUpdate(SQL1);
     cn1.close();
     }
     catch(Exception e){}
     }
     }
     );    
    }}

Answer 2

请问tom2005(快乐着)为什么加一个try catch 要捕获异常就没问题了，难道用jdbc时必须加try catch 吗，谢谢

Answer 3

unreported exception java.lang.ClassNotFoundException; must be caught or declared to be thrown如果再遇到,就try{ } catch{ } .... 
Class  Not  Found  Exception  ....  Are You understand?

Answer 4

Must Catch Your Operation!

Answer 5

mport java.awt.*;
import java.awt.event.*;
import java.sql.*;
import javax.swing.*;public class SqlTest
{
public static void main(String[] args)
{
JFrame frame = new JDataFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show();
}
}
class JDataFrame extends JFrame 
{
    
    /**
     * The constructor.
     */ 
     static String driver="com.microsoft.jdbc.sqlserver.SQLServerDriver"; 
     static String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=northwind";
     JTextField txtComName=null;
     JTextField txtAdr=null;
     JTextField txtCity=null;
     String strId=null;     public JDataFrame() 
     {
     
        JLabel labcomname=new JLabel();//customernamelabel  
        labcomname.setSize(40,4);
        JLabel labadr=new JLabel();//customeraddress
        labadr.setSize(40,4);
        JLabel labcity=new JLabel();//customercity
        labcity.setSize(40,4);
        txtComName=new JTextField(20);//companyname
        txtComName.setSize(20,4);
        txtAdr=new JTextField(20);
        txtAdr.setSize(40,4);
        txtCity=new JTextField(20);
        txtCity.setSize(40,4);
        Container container=this.getContentPane();
        JPanel selPanel=new JPanel();
        selPanel.setLayout(new GridLayout(3,1));
        selPanel.add(labcomname);
        selPanel.add(labadr);
        selPanel.add(labcity);
        selPanel.setSize(200,100);
        JPanel updatePanel=new JPanel();
        updatePanel.setLayout(new FlowLayout());
        updatePanel.add(txtComName);
        updatePanel.add(txtAdr);
        updatePanel.add(txtCity);
        updatePanel.setSize(200,100);
        JButton butOK=new JButton("OK");
        butOK.setSize(20,4);
        
        Container myFrm=this.getContentPane();
        myFrm.setLayout(new BorderLayout());
        myFrm.add(selPanel,BorderLayout.NORTH);
        myFrm.add(updatePanel,BorderLayout.CENTER);
        myFrm.add(butOK,BorderLayout.SOUTH);
        
        //read database
       
        try
        {
        Class.forName(driver);
    
        Connection cn=DriverManager.getConnection(url,"sa","king");
        String SQL="Select CompanyName,Address,City,CustomerID From Customers";
        Statement stmt=cn.createStatement();
        ResultSet rs=stmt.executeQuery(SQL);
        if (rs.next())
        {
         labcomname.setText("companyname:" + rs.getString("CompanyName") + "|");
         labadr.setText("companyaddress:" + rs.getString("Address") + "|");
         labcity.setText("companycity:"+ rs.getString("city"));
         strId=rs.getString("CustomerID");
        }
        rs.close();
        cn.close();
         }
         catch (Exception e)      
         {
           JOptionPane.showMessageDialog(null,e.getMessage());
         }
        this.setSize(400,240);
        this.setVisible(true);
       // container.setLayout(new BorderLayout());
        
     butOK.addActionListener(
     new ActionListener(){
     public void actionPerformed(ActionEvent event)
     {
     Connection cn1=null;
     try
     {
    
     Class.forName(driver);
     cn1=DriverManager.getConnection(url,"sa","king");
     Statement stmt1=cn1.createStatement();
     String SQL1="Update Customers Set CompanyName='" + txtComName.getText() + "',Address='"
     + txtAdr.getText() + "',city='" + txtCity.getText() + "' Where CustomerID='" + strId + "'";
     stmt1.executeUpdate(SQL1);
     cn1.close();
     }
     catch(SQLException se)
     {
     System.out.println("SQL occur exception");
     }
     catch(ClassNotFoundException snfe)
     {
     System.out.println("Class not found");
     }
     finally
     {
    
     }
     }
     }
     );    
    }
//已经编译通过了，java对安全性要求特别高，对可能出现的异常一定要进行处理，否则，编译器会报错