Question

I’m trying to make my DAO work this way:

    public void incrementNumber(long id) throws Exception{
        Session session = factory.openSession();
        Number n = (Number)session.load(Number.class, id);
        n.setNumber(n.getNumber() +5);
//      throw new IllegalArgumentException("BLAH");
        session.close();
    }

1. By commenting out the exception, the update will commit.
2. By un-commenting(?) the exception, it will rollback.

Any way to achieve this? Note: the transaction part is done in a service, under a transactional annotation.

Answer 1

DAO is mainly responsible for persistence operations .It should only provide CRUD and some finder methods relating to a particular entity.

IMO , your method more like a business operation rather than the persistence operations . As you have the service layer , I suggest you move this method to it.

So , your NumberDAO may look like this:

public class NumberDAO {

     public Number loadById(long id){ }

}

And you NumberService may look like this:

public class NumberService{

        //Inject by DI containers , or setter / constructor
        NumberDAO numberDAO;

         public void incrementNumber(long id , int increaseAmount) throws Exception{

                Number n = (Number) numberDAO.loadById(id);

                if (XXXXXXXX) 
                    throws new IllegalArgumentException("BLAH BLAH BLAH BLAH");

                n.setNumber(n.getNumber() +increaseAmount);
         }

}

As you use transactional annotation in the service layer , it will commit automatically if your service method returns successfully .In case of any exceptions throw before the method returns , the transaction will rollback automatically .