DAO and DTO

Question

In the following piece of code:-
package com.informit.myejb.dao;
public interface SampleDAO
public SampleModel create( long id, String name, String data ) throws
SampleDAOException;
public void delete( long id ) throws SampleDAOException;
public void update( long id, SampleModel model ) throws
SampleDAOException;
public SampleModel[] findByName( String name ) throws
SampleDAOException;
public SampleModel findById( long id ) throws SampleDAOException;
}we are creating a DTO named sampleModel. Now considering that I just need one value out of the whole table. Wouldn't creating the whole DTO object be a waste of time effort and memory, specially if each time we hae to access the DTO we have to create a new one. specially if the keys being passed to the method are used only once.
I understand the concept of separation of concerns but I am concerned over here about the amount of effort required to create these DAOs and DTOs specially in cases where only one or two fields are required.
To me it seems like an over kill.
Any comments.

Answer 1

well Martin Fowlwer does propose IdentityMap pattern in such a case where he says that thes objects should be stored in a Map with the primary key being the key for the map. So next time you need an object you check with the map if it exists or not and if it doesnot you try to grab it again.
But IMHO if the hit ratio(no. of times the same data is used again) is less these Maps might pose a nightmare in terms of memory and garbage collection.
So should one use IdentityMap or avoid it?
What do you think.