单一职责原则java
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。
代码按照图中顺序
package test1; 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"; public static String db_user = "root"; public static String db_pass = "123456"; 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"); } } }
package test1; 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"); } } }
package test1; public class MainClass { public static void main(String[] args) { LoginForm loginForm=new LoginForm() ; //调用 loginForm.display(); } } //run此文件
package test1; 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; } }
sql
CREATE TABLE `user` ( `username` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL, `password` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci DEFAULT NULL ) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic; -- ---------------------------- -- Records of user -- ---------------------------- INSERT INTO `user` VALUES ('张三', '123456'); SET FOREIGN_KEY_CHECKS = 1;
