As said
We have a distinct layer for business logic (usually called Service layer)
Domain-Driven-Design (DDD) states you should put business logic inside your domain model. And, believe me, it is really good. As said by POJO in Action book about Service layer
- It is Use Case driven
- It can define Transaction boundaries
Before
@Service
public class BidServiceImpl implements BidService {
@Autowired
private ItemRepository itemRepository;
public void placeBid(Integer itemId, User bidder, BigDecimal amount) {
Item item = itemRepository.getById(itemId);
if(amount.compareTo(new BigDecimal("0.00")) <= 0)
throw new IllegalStateException("Amount must be greater than zero");
if(!bidder.isEnabled())
throw new IllegalStateException("Disabled bidder");
item.getBidList().add(new Bid(bidder, amount));
}
}
After
@Service
public class BidServiceImpl implements BidService {
@Autowired
private ItemRepository itemRepository;
public void placeBid(Integer itemId, User bidder, BigDecimal amount) {
// itemRepository will retrieve a managed Item instance
Item item = itemRepository.getById(itemId);
item.placeBid(bidder, amount);
}
}
Your domain logic is show as follows
@Entity
public class Item implements Serializable {
private List<Bid> bidList = new ArrayList<Bid>();
@OneToMany(cascade=CascadeType.ALL)
public List<Bid> getBidList() {
return this.bidList;
}
public void placeBid(User bidder, BigDecimal amount) {
if(amount.compareTo(new BigDecimal("0.00")) <= 0)
throw new IllegalStateException("Amount must be greater than zero");
if(!bidder.isEnabled())
throw new IllegalStateException("Disabled bidder");
/**
* By using Automatic Dirty Checking
*
* Hibernate will save our Bid
*/
item.getBidList().add(new Bid(bidder, amount));
}
}
When using Domain-Driven-Design, your business logic lives in the right place. But, sometimes, it could be a good idea to define your business logic inside your Service layer. See here why