Dan, The way I would solve this is with a one-to-many relationship, and what is termed "complex" models in Torque speak. Basically as part of the construction of the "owning" DAO, in your case Customer, it builds a collection (usually a simple Vector) of dependent objects, which are called with a get<OtherTable>() method, in this case "customerDaoImpl.getContacts();".
Its not a good idea to make them call methods of each other, but placing groups into a collection inside a composite object is fine, if you wanted to make it even more bullet-proof, use interfaces to abstract all DAOs, as long as the contained DAO object implements the interface all will keep spinning. Best regards, Cameron Gray Operations Director, UltraSpeed UK Limited Tel/Fax: 0800 689 9898 W: www.ultraspeed.co.uk AIM: UltraSpeedNetOps ICQ: 159796008 Murphy's Third Law: In any field of scientific endeavor, anything that can go wrong will go wrong. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dan Allen Sent: 09 December 2003 21:45 To: [EMAIL PROTECTED] Subject: [Struts-apps] question on DAO design THE QUESTION: Does it (make sense|is it general practice) to call one DAO from within another DAO? I was hoping that someone on this list could help me free myself from the shackles of confusion. At my job, I am developing a web application using JDBC (required unfortunately) to abstract the data access but I am running into a problem, one I realize would be solved by Hibernate, but interesting to attempt to tackle anyway. Assume I have two entities in my system (amoungst many others), Contacts and Customers. Contacts are the end user, and the customers are the accounts (think of it like online banking). The contacts can manipulate these customer accounts by ordering, viewing, requesting service. Naturally I made a ContactDAO which retrieves contacts, profile information, etc. My next object is CustomerDAO which retrieves information about the customer (the agency name, mailing address, etc). A contact can be associated with many customers and vice versa, each relationship represented by a role. Naturally I created a CustomerContact object which links these two entities: +----------------+ | CustomerContact| + ---------------+ | roleName | | contact | | customer | +----------------+ Here comes my problem. My ContactDAO takes care of the data access to the contact table. The CustomerDAO however contains methods which must get at the contact data with queries such as getContactsForCustomer and getCustomersForContact which return CustomerContact[] arrays (since the ContactDAO shouldn't have methods dealing with the customer relationship since it is not a dependency of a contact, but is of a customer). In my CustomerDAO, to create the CustomerContact transfer object, I need to talk to my ContactDAO to get that information, if I don't want to duplicate the calls in the CustomerDAO. In short, at some point, one DAO needs to use the methods in the other DAO since there is cross over. The main confusion here is how to deal with information that seems to want to be in both DAOs. THE QUESTION: Does it (make sense|is it general practice) to call one DAO from within another DAO? Thanks, Dan -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Daniel Allen, <[EMAIL PROTECTED]> http://www.mojavelinux.com/ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Microsoft's Law of Software Engineering: Don't worry if it doesn't work right. If everything did, we'd be out of a job. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ------------------------------------------------------- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click _______________________________________________ Struts-apps mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/struts-apps ------------------------------------------------------- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id78&alloc_id371&op=click _______________________________________________ Struts-apps mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/struts-apps
