单一职责原则实例——登录模块

今天主要完成了软件设计实验一中的编程问题

[实验任务二]：单一职责原则

登录模块在实际项目开发中很常见，请按照教材28页利用单一职责原则重构后的类图实现这一模块。

1、新建 java project 

2、导入jar包

mysql-connector-java-8.0.22.jar

        * 此处注意jar包的版本不能过低，否则数据库连接失败

3、创建数据库和表

4、DBUtil.java

package Test;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBUtil {

	public static String db_url = "jdbc:mysql://localhost:3306/first?serverTimezone=GMT%2B8&useSSL=false";
	public static String db_user = "root";
	public static String db_pass = "liutianwen0613";

	public static Connection getConn () {
		Connection conn = null;

		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
			conn = DriverManager.getConnection(db_url, db_user, db_pass);
		} catch (Exception e) {
			e.printStackTrace();
		}

		return conn;
	}//end getConn

	public static void close (Statement state, Connection conn) {
		if (state != null) {
			try {
				state.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}

		if (conn != null) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	public static void close (ResultSet rs, Statement state, Connection conn) {
		if (rs != null) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}

		if (state != null) {
			try {
				state.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}

		if (conn != null) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	public static void main(String[] args) throws SQLException {
		Connection conn = getConn();
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		String sql ="select * from user";
		pstmt = conn.prepareStatement(sql);
		rs = pstmt.executeQuery();
		if(rs.next()){
			System.out.println("连接成功");
		}else{
			System.out.println("连接失败");
		}
	}
}

5、UserDao.java

package Test;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class UserDao {
	public boolean findUser(String username, String password) {
		//准备SQL语句
		String sql = "select * from user where username ='" + username + "'";
		Connection conn= DBUtil.getConn();
		//创建语句传输对象
		Statement state = null;
		ResultSet rs= null;
		int flag=0;
		String c_password=null;
		try {
			state = conn.createStatement();
			rs = state.executeQuery(sql);
			while(rs.next()) {
				++flag;
			    c_password=rs.getString("password");
			}	if (flag == 0) {
				return false;
			}
			if (!password.equals(c_password)) {   //判断密码
				return false;
			}
	}catch (SQLException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}finally {
		 DBUtil.close(rs, state, conn);
	}
	return true;
		}
}

6、LoginForm.java

package Test;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class LoginForm extends JFrame {
	
	private static final long serialVersionUID = 1L;
	private  UserDao dao = new UserDao();
	//设置按钮组件
    
    private  JButton jb=new JButton("登录");	//添加一个登录按钮
    private JButton button=new JButton("重置");	//添加一个确定按钮
    //设置文本框组件
    private JTextField username = new JTextField();//用户名框
    private JPasswordField password = new JPasswordField();//密码框：为加密的***
    
    JLabel user_name=new JLabel("账号：");//设置左侧用户名文字
    JLabel pass_word=new JLabel("密码：");//设置左侧密码文字
    
    public void init()
    {
	/* 组件绝对位置  */
	user_name.setBounds(50, 70, 300, 25);
	pass_word.setBounds(50, 130, 200, 25);
		
	username.setBounds(110, 70, 300, 25);//设置用户名框的宽，高，x值，y值
	password.setBounds(110, 130, 300, 25);//设置密码框的宽，高，x值，y值
		
	button.setBounds(315, 225, 90, 20);//设置确定按钮的宽，高，x值，y值
	jb.setBounds(95, 225, 90, 20);//设置确定按钮的宽，高，x值，y值
		
		
	/* 组件透明化*/
	user_name.setOpaque(false);
	pass_word.setOpaque(false);
		
		
	 //监听事件
	jb.addActionListener(new ActionListener(){		//为确定按钮添加监听事件
				
		@SuppressWarnings("deprecation")
		public void actionPerformed(ActionEvent arg0) {
		    validate(username.getText().trim(),password.getText().trim());
		}
	});
		
			
	//重置按钮
	button.addActionListener(new ActionListener(){		//为重置按钮添加监听事件
		//同时清空name、password的数据
		public void actionPerformed(ActionEvent arg0) {
			// TODO 自动生成方法存根
			username.setText("");
			password.setText("");
		}
	});
		
    }
	
    public void display()
     {
	JFrame f =new JFrame();
	f.setTitle("登录页面");
        //窗口退出行为
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //设置窗口大小不可变
        f.setResizable(false);
        //设置窗口打开居中
        f.setLocationRelativeTo(null);
        //窗口大小
        f.setSize(500, 300);
       
        init();
        
        //添加组件
        Container contentPanel= new Container();//添加一个contentPanel容器
		 contentPanel.setLayout(null);//设置添加的contentPanel容器为流布局管理器
		 contentPanel.add(user_name);
		 contentPanel.add(pass_word);
		 contentPanel.add(username);
		 contentPanel.add(password);
		 contentPanel.add(jb);
		 contentPanel.add(button);
		
			f.add(contentPanel); 
			 //展示窗口
	        f.setVisible(true);
	}
	

   public  void  validate(String username,String password)
	 {
		
           if(username.trim().length()==0||password.trim().length()==0){
	   JOptionPane.showMessageDialog(null, "用户名,密码不允许为空");
				
		return;
	     }
		 
	   if(dao.findUser(username, password))
	    {
			  
		JOptionPane.showMessageDialog(null, "登录成功！");
			  
			 
		  }else {
			  JOptionPane.showMessageDialog(null, "用户名或密码错误");
			 
		  }
		 
	   }	
	
}

7、MainClass.java

package Test;

public class MainClass {
	 
	 public static void main(String[] args)
	 {
			LoginForm loginForm=new LoginForm() ;	//调用
			loginForm.display();
			   
	 }

}

效果截图：