Question

I’m building a SpringMVC project for the first time and just wanted some feedback on my design.

At the moment I have the following UserDao

package org.myproj.com.dao;

import org.myproj.com.entity.User;

public interface UserDao {
    public User getById(Long id);
}

This is implemented by the UserDaoImpl

package org.myproj.com.dao;

import org.myproj.com.entity.User;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

@Repository("userDao")
public class UserDaoImpl implements UserDao{


    @Autowired
    private SessionFactory sessionFactory;

    public User getById(Long id) {
        return (User) sessionFactory.getCurrentSession().get(User.class, id);
    }

}

I then have a service layer, UserService

package org.myproj.com.service;

import org.myproj.com.entity.User;

public interface UserService {
    public User getById(Long id);
}

With an impl, UserServiceImpl

package org.myproj.com.service;

import org.myproj.com.dao.UserDao;
import org.myproj.com.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@Service("userService")
@Transactional
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;


    public UserServiceImpl() {
    }

    @Transactional
    public User getById(Long id) {
        return userDao.getById(id);
    }

}

This is then accessed by my servlet with…

@Autowired
    private UserService userService;

User user = userService.getById(1L);

I can’t help but feel that my Dao and my Service are replicating a lot. I’m considering using the service layer to add stuff like roles etc and the Dao do the business logic.

What do you think of this design? Is it acceptable?

Answer 1

IMHO it’s best to put the semantics of the business transactions into the service layer, and the data-side building blocks into the dao layer. The dao layer is then the data API used by the services. So, while the dao layer might have UserDao with a findByName(String username) method, the service layer wouldn’t. Instead, the service layer would have a SecurityService with a authenticateUser(String username) and that would, among other things, call userDao.findByName(username). And if you have a UserDetailService with a addEmailAddressToUser(String username), well, that would call the same dao method.