使用java书写一个运用数据访问层、业务逻辑层、UI层三层架构设计完成用户管理模块，完成用户登录业务设计的代码

好的，下面是一个简单的示例代码：

首先是数据访问层（DAO）：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {
    private Connection conn;

    public UserDAO() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/mydb";
            String username = "root";
            String password = "123456";
            conn = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public boolean checkUser(String username, String password) {
        boolean result = false;
        try {
            String sql = "SELECT * FROM users WHERE username=? AND password=?";
            PreparedStatement stmt = conn.prepareStatement(sql);
            stmt.setString(1, username);
            stmt.setString(2, password);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                result = true;
            }
            rs.close();
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }
}

接下来是业务逻辑层（Service）：

public class UserService {
    private UserDAO userDao;

    public UserService() {
        userDao = new UserDAO();
    }

    public boolean checkUser(String username, String password) {
        return userDao.checkUser(username, password);
    }
}

最后是UI层（UI）：

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class UserUI extends JFrame {
    private JTextField usernameField;
    private JPasswordField passwordField;
    private JButton loginButton;

    public UserUI() {
        super("User Login");

        JPanel formPanel = new JPanel(new BorderLayout());

        JPanel fieldPanel = new JPanel(new FlowLayout());
        fieldPanel.add(new JLabel("Username:"));
        usernameField = new JTextField(20);
        fieldPanel.add(usernameField);
        fieldPanel.add(new JLabel("Password:"));
        passwordField = new JPasswordField(20);
        fieldPanel.add(passwordField);

        JPanel buttonPanel = new JPanel(new FlowLayout());
        loginButton = new JButton("Login");
        loginButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String username = usernameField.getText();
                String password = new String(passwordField.getPassword());
                UserService userService = new UserService();
                if (userService.checkUser(username, password)) {
                    System.out.println("Login success!");
                } else {
                    System.out.println("Login failed!");
                }
            }
        });
        buttonPanel.add(loginButton);

        formPanel.add(fieldPanel, BorderLayout.CENTER);
        formPanel.add(buttonPanel, BorderLayout.SOUTH);

        add(formPanel);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);
        setVisible(true);
    }

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

这个示例代码实现了一个简单的用户登录功能，使用了三层架构设计，其中数据访问层使用了MySQL数据库，业务逻辑层通过调用数据访问层的方法实现了用户登录的业务逻辑，UI层使用了Java Swing库实现了一个简单的登录窗口。