Sebastian Ho wrote:
Say I retrieve a TO from database and convert it into a actionForm for display. In this case I have 4 fields for my actionForm but 10 in my TO. (6 are not needed for display). A user updates the 4 fields and the action convert those into TO. In this case, the other 6 fields will be reset to null(or empty) in my database!
To prevent this, I actually need to use hidden fields in my JSP or some other ugly solutions in my Action class. They are still dependent on each others afterall.
You can handle this several ways...
For example, one solution is you create a TransferObject that refers to only the fields you care about - in this case the 4 fields you mentioned. So your call to the business layer would return that TransferObject and you could then convert that easily to your form (using BeanUtils). Then going back the other way your business layer would take as an arguemnt the same type of TransferObject.
I actually don't prefer the above, though, because say later on you decide you want to add another field to your form now your backend has to worry about handling a new object with different fields.
I think the best solution is to simply make another call to get back the initial TO from the db, then simply use BeanUtils to populate that TO with the form fields. It will only set the fields in which it has the same names for so your other data will be fine.
So it looks like...
TransferObject to = BackendEnd.getMyTransferObject(..); MyForm myForm = (MyForm)form; BeanUtils.copyProperties( to, myForm); BackEnd.doUpdate( to );
Pretty simple I think. Just make sure your ActionForm doesn't contain properties that you don't care about editing otherwise it will over-write the TO properties. If the JSP form is going to be very dyanmic, as in it will sometimes have some properties and sometimes have others, then you will have to use more complex 'tricks' such as using hidden variables.. or I'd just prefer to manually set the TO fields in the Action.
-- Rick
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