logon.java

学习java的几个好例子

//**************************************
// Name: A Swing Logon Window
// Description:Beginners rate me on this one !! its a logon screen , its give users access to your application!! enjoy
// By: Xolani
//
//
// Inputs:username and password .....
//
// Returns:returns 1 if user details where found in the database , 0 if not
//
//Assumes:Must create a database with the table Users(UserName,Password) or must rename my odbc connection to according to his/her database ....
//
//Side Effects:your database must have the table Users(UserName,Password) .....
//This code is copyrighted and has limited warranties.
//Please see http://www.Planet-Source-Code.com/xq/ASP/txtCodeId.3017/lngWId.2/qx/vb/scripts/ShowCode.htm
//for details.
//**************************************

/* @ Xolani Gwaqa 2002
*(Swing) Logon Window 
*The database must have Users Table as 
*Users(UserName,Password) 
*Also change the odbc name 'monthly' to suite you!!!!
*/
import java.io.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.sql.*;
import java.util.*;


    public class Logon extends JFrame implements ActionListener {
    	public JButton bConn,bClose;
    	private JTextField UserName;
    	private JPasswordField Password; 
    	public String sName,sPassword;
    	public String url ="jdbc:odbc:monthly";
    	public Connection conn;
    	public Statement stmt;
    public Logon()


        {
        setTitle("Login Screen");
        
        
        // GUI ******************
        	
        	bConn = new JButton("Login");
        	bClose = new JButton("Close");
        	bConn.addActionListener(this);
        	bClose.addActionListener(this);
        	
        	JPanel p = new JPanel();
        	p.add(bConn);
        	p.add(bClose);
        	
        	JLabel lname = new JLabel("UserName");
        	JLabel lpassword = new JLabel("Password");
        	
        	UserName = new JTextField(10);
        	Password = new JPasswordField(10);
        	
        	JPanel p1 = new JPanel();
        	p1.setLayout(new GridLayout(2,2));
        	p1.add(lname);
        	p1.add(UserName);
        	p1.add(lpassword);
        	p1.add(Password);
        	
        	p1.add(UserName);
        	p1.add(Password);
        	
        	getContentPane().add(p1,"North");
        	getContentPane().add(p,"Center");
        	
        	//*** End GUI***********************************
        	


            	 addWindowListener(new WindowAdapter() {
            


                	public void windowClosing(WindowEvent ev){
                	 	
                	 	System.exit(0);
                	}
            });
            //set the position in the screen
            int inset = 250;
            Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
            setBounds(inset, inset, screenSize.width - inset*2,screenSize.height-inset*2);
            setSize( 300, 100);
            setVisible( true );
            setResizable(false);
            
            
            try


                {
                	 Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 
            }
            catch(Exception e)


                {
                	 System.out.println(e.toString());
            }
            try


                {
                	 conn = DriverManager.getConnection(url,"sa","");
            }
            catch(Exception e)


                {
                	 System.out.println("Could not load Driver"); 
            }	
        }
        public int CheckLogin(String UserName,String Password)


            {
            	try


                	{
                			stmt = conn.createStatement();	
                			
                			//check against the database if user details do exists	
                ResultSet rs = stmt.executeQuery("select * from Users where Username = '" + UserName + "' and Password = '" + Password + "'");
                				
                			System.out.println("Wait... ... ....");
                			
                			if(rs.next())


                    			{
                    				return 1; // user details exists 
                    		}
                    			else


                        			{
                        				return 0; // user details do not exists
                        				
                        			}
                        	
                        		//	stmt.close();
                        			//	conn.close();
                        	 }
                        	 catch(SQLException ee)


                            	 {
                            		 System.out.println(ee.toString());
                            		 return 0;
                            	 }
                            	 
                            	 
                        }


                            public static void main(String args[]){
                            Logon theWindow =new Logon();//create new instance of Logon
                            theWindow.show();
                        } 


                            public void actionPerformed(ActionEvent e){
                            String User_Name,Pass_Word;
                            User_Name = UserName.getText();
                            Pass_Word = Password.getText();
                            int Check;
                            	if(e.getActionCommand().equals("Login"))


                                	{
                                		
                                		
                                		Check =	CheckLogin(User_Name,Pass_Word);
                                		
                                		if(Check==1)


                                    		{
                                    //this means that your logon details where correct , then you can do anything @ this step
                                    			
                                    			hide();
                                    	}
                                    	else


                                        	{
                                        	JOptionPane.showMessageDialog(null,String.valueOf("Ops! Your logon details are not correct,please try again!"));
                                        	}
                                        
                                        	}
                                        	else
                                        	System.exit(0);
                                    }
                                }