Develop the Business Service Tier

@RunWith( SpringJUnit4ClassRunner.class )
@ContextConfiguration( locations = { "classpath:context.xml" } )
@TransactionConfiguration( defaultRollback = true )
@Transactional
public class UserGroupServiceImplTest {

	@Autowired
	private UserService userService;
	
	@Autowired
	private GroupService groupService;
	
	@Autowired
	private UserGroupService userGroupService;
	
	@Test
	public void testFindAll() {
		Assert.assertEquals(0L, userGroupService.findAll().size());
	}
}

@Service
@Transactional
public class UserGroupServiceImpl implements UserGroupService {

	@Autowired
	private GroupDao groupDao;
	
	@Autowired
	private UserDao userDao;
	
	@Autowired
	private UserGroupDao userGroupDao;
	
	@Autowired
	private UserMapper userMapper;
	
	@Autowired
	private GroupMapper groupMapper;
		
	@Override
	public List<UserGroupDto> findAll() {
		List<UserGroupDto> userGroupDtos = new ArrayList<UserGroupDto>();
		List<User> userList = userGroupDao.getAll();
		for(User user : userList) {			
			UserDto userDto = userMapper.mapEntityToDto(user);			
			Set<Group> groups = user.getGroups();
			for(Group group : groups) {
				UserGroupDto userGroupDto = new UserGroupDto();
				userGroupDto.setUserDto(userDto);
				GroupDto groupDto = groupMapper.mapEntityToDto(group);
				userGroupDto.setGroupDto(groupDto);
				userGroupDtos.add(userGroupDto);
			}			
		}
		return userGroupDtos;
	}
}