给我写一个接口返回user的所有信息，用userService

好的，我假设你使用的是Java语言，下面是一个简单的实现：

首先，在你的项目中创建一个UserService接口，声明如下方法：

public interface UserService {
    User getUserById(int id);
    List<User> getAllUsers();
    void addUser(User user);
    void updateUser(User user);
    void deleteUser(int id);
}

然后，创建一个User类，用于表示用户信息：

public class User {
    private int id;
    private String name;
    private String email;
    // 其他用户信息的属性和方法
    
    // 构造方法、getter和setter方法等省略
}

接下来，你可以使用任何一种数据库访问框架来实现UserService接口，这里我以JDBC为例子来实现，具体代码如下：

public class JdbcUserService implements UserService {
    private Connection conn;
    
    // 构造方法，初始化数据库连接
    public JdbcUserService() {
        try {
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public User getUserById(int id) {
        User user = null;
        try (PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE id = ?")) {
            stmt.setInt(1, id);
            try (ResultSet rs = stmt.executeQuery()) {
                if (rs.next()) {
                    user = new User();
                    user.setId(rs.getInt("id"));
                    user.setName(rs.getString("name"));
                    user.setEmail(rs.getString("email"));
                    // 设置其他用户信息的属性值
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return user;
    }

    @Override
    public List<User> getAllUsers() {
        List<User> userList = new ArrayList<>();
        try (Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT * FROM users")) {
            while (rs.next()) {
                User user = new User();
                user.setId(rs.getInt("id"));
                user.setName(rs.getString("name"));
                user.setEmail(rs.getString("email"));
                // 设置其他用户信息的属性值
                userList.add(user);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return userList;
    }

    @Override
    public void addUser(User user) {
        String sql = "INSERT INTO users(name, email, ...) VALUES (?, ?, ...)";
        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, user.getName());
            stmt.setString(2, user.getEmail());
            // 设置其他用户信息的属性值
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void updateUser(User user) {
        String sql = "UPDATE users SET name = ?, email = ?, ... WHERE id = ?";
        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, user.getName());
            stmt.setString(2, user.getEmail());
            // 设置其他用户信息的属性值
            stmt.setInt(10, user.getId());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void deleteUser(int id) {
        try (PreparedStatement stmt = conn.prepareStatement("DELETE FROM users WHERE id = ?")) {
            stmt.setInt(1, id);
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

最后，你可以在你的Controller中注入UserService，然后调用它的方法来获取用户信息：

@Controller
@RequestMapping("/user")
public class UserController {
    private UserService userService;

    @Autowired
    public UserController(UserService userService) {
        this.userService = userService;
    }

    @GetMapping("/{id}")
    public String getUserById(@PathVariable int id, Model model) {
        User user = userService.getUserById(id);
        model.addAttribute("user", user);
        return "user";
    }

    @GetMapping("/all")
    public String getAllUsers(Model model) {
        List<User> userList = userService.getAllUsers();
        model.addAttribute("userList", userList);
        return "userList";
    }

    // 其他Controller方法省略
}