java基础之登录程序

注：此版本仅供学习使用！

Login.java

 import java.awt.Font;
 import java.awt.event.*;
 import java.sql.*;

 import javax.swing.*;
 import javax.swing.border.EmptyBorder;

 @SuppressWarnings("serial")
 public class Login extends JFrame {
     JLabel jla_tips;
     JLabel jla_username;
     JTextField jtf_username;
     JLabel jla_password;
     JPasswordField jpf_password;
     JButton jbt_login;
     JButton jbt_cancel;
     int count=0;

     public Login() {
         ImageIcon icon = new ImageIcon("images/favicon.png");
         setIconImage(icon.getImage());

         JPanel contentPane = new JPanel();
         contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
         setContentPane(contentPane);
         contentPane.setLayout(null);

         jla_tips = new JLabel();
         jla_tips.setBounds(155, 40, 200, 25);
         contentPane.add(jla_tips);

         jla_username = new JLabel("用户名:");
         jla_username.setBounds(80, 70, 60, 25);
         contentPane.add(jla_username);

         jtf_username = new JTextField();
         jtf_username.setHorizontalAlignment(JTextField.LEFT);
         jtf_username.setBounds(150, 70, 150, 25);
         contentPane.add(jtf_username);

         jla_password = new JLabel("密  码:");
         jla_password.setBounds(80, 120, 60, 25);
         contentPane.add(jla_password);

         jpf_password = new JPasswordField();
         jpf_password.setBounds(150, 120, 150, 25);
         contentPane.add(jpf_password);

         // 登录按钮
         jbt_login = new JButton("登录");
         jbt_login.setFocusPainted(false);
         jbt_login.setBounds(150, 170, 70, 30);
         contentPane.add(jbt_login);
         jbt_login.addActionListener(new loginListener());
         jpf_password.addActionListener(new loginListener());

         // 置空按钮
         jbt_cancel = new JButton("取消");
         jbt_cancel.setFocusPainted(false);
         jbt_cancel.setBounds(235, 170, 70, 30);
         contentPane.add(jbt_cancel);
         jbt_cancel.addActionListener(new cancelListener());

         // 背景图
         Icon login3 = new ImageIcon("images/login3.jpg");
         JLabel jla_login3 = new JLabel(login3);
         jla_login3.setBounds(0, 0, 450, 300);
         contentPane.add(jla_login3);

         // 字体设置
         Font fontstr = new Font("宋体", Font.PLAIN, 14);
         jla_username.setFont(fontstr);
         jla_password.setFont(fontstr);
         jla_tips.setFont(fontstr);
         jbt_login.setFont(fontstr);
         jbt_cancel.setFont(fontstr);

         setTitle("登录");
         setSize(450, 300);
         setLocationRelativeTo(null);
         setResizable(false);
         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         setVisible(true);
     }

     public class cancelListener implements ActionListener{
         @Override
         public void actionPerformed(ActionEvent arg0) {
             jtf_username.setText(null);
             jpf_password.setText(null);
         }

     }
     public class loginListener implements ActionListener {
         @Override
         public void actionPerformed(ActionEvent e) {
             String username = jtf_username.getText().trim();
             char[] values = jpf_password.getPassword();
             String password = new String(values);
             if (username != null && username.length() != 0 && password != null
                     && password.length() != 0) {
                 try {
                     // 1.注册驱动
                     Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
                     // 2.建立连接
                     // 2.1连接串
                     String DBurl = "jdbc:sqlserver://localhost:1433;DatabaseName=JavaDB";
                     String DBname="sa";
                     String DBpwd="940523";
                     Connection con = DriverManager.getConnection(DBurl,DBname,DBpwd);

                     // 创建会话
 //                    Statement st = con.createStatement();
 //                    String sql = "select count(*) as cnt from T_user where username='"
 //                            + username + "' and password='" + password + "'";
 //                    ResultSet rs = st.executeQuery(sql);

                     /*
                      * 防止SQL注入
                      */
                     String sql = "select count(*) as cnt from T_user where username=? and password=?";
                     PreparedStatement st = con.prepareStatement(sql);
                     st.setString(1, username);
                     st.setString(2, password);
                     String sql2 = "select count(*) as cnt from T_user where username=?";
                     PreparedStatement st2 = con.prepareStatement(sql2);
                     st2.setString(1, username);
                     // 结果集
                     ResultSet rs = st.executeQuery();
                     ResultSet rs2 = st2.executeQuery();

                     rs.next();
                     rs2.next();
                     if (rs.getInt("cnt") > 0) {
                         setVisible(false);
                         new Hello();
                     } else if (rs2.getInt("cnt") == 0) {
                         JOptionPane.showMessageDialog(null, "无该用户!");
                     }else {
                         jla_tips.setText("密码错误!");
                         count++;
                         if(count==3){
                             JOptionPane.showMessageDialog(null, "登录失败超过三次!");
                             System.exit(0);
                         }
                     }
                 } catch (Exception ex) {
                     ex.printStackTrace();
                 }
             } else {
                 if (username.length() == 0 && password.length() == 0)
                     jla_tips.setText("帐号与密码均不能为空!");
                 else if (username.length() == 0)
                     jla_tips.setText("帐号不能为空!");
                 else if (password.length() == 0)
                     jla_tips.setText("密码不能为空!");
             }
         }
     }

     public static void main(String[] args) {
         new Login();
     }
 }

hello.java

 import java.awt.Font;
 import javax.swing.*;
 import javax.swing.border.EmptyBorder;

 @SuppressWarnings("serial")
 public class Hello extends JFrame {
     JLabel jla_title;

     public Hello() {
         ImageIcon icon = new ImageIcon("images/favicon.png");
         setIconImage(icon.getImage());

         JPanel contentPane = new JPanel();
         contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
         setContentPane(contentPane);
         contentPane.setLayout(null);

         jla_title = new JLabel();
         jla_title.setText("欢迎使用本软件!");
         jla_title.setBounds(120, 100, 200, 25);
         // 字体设置
         Font fontstr = new Font("宋体", Font.PLAIN, 26);
         jla_title.setFont(fontstr);
         contentPane.add(jla_title);

         setTitle("欢迎界面");
         setSize(450, 300);
         setLocationRelativeTo(null);
         setResizable(false);
         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         setVisible(true);
     }

     // public static void main(String[] args) {
     // new Hello();
     // }
 }

下载链接:http://pan.baidu.com/s/1pJAtf1T密码: 1kkz