Your service, as it stands, is simply delegating everything to the underlying DAO. This may be desired sometimes, but typically I put "business logic" in the service layer. Putting logic in the service layer will help keep your controller layer pretty light too.

A service can use one or more DAOs to accomplish the task it needs. So consider a simple bank system, where I have a AccountDao

public class AccountDao implements GenericDao<Account, Long> {
  // your save, insert, delete, find, etc
}

Then in my service, I would put "makePayment" or something

@Service
public class AccountService {

   @Autowired
   private AccountDao dao;

   @Transactional
   public void makePayment(Long fromId, Long toId, double amount) {
      Account from = dao.find(fromId);
      from.withdrawl(amount);

      Account to = dao.find(toId);
      to.deposit(amount);

      dao.save(from);
      dao.save(to);
   }
}

Use transactions on your service layer, to give you more control over which operations need to be in the same transaction.