On Sat Aug 13 09:47:22 2011, John Huss wrote:
Is it possible to use ROP (serialized data objects) and regular data objects at
the same time? In EOF each editing context is backed by a different object
store and the remote objects have a special remote object store. As long as
the two types of objects are separate you can use both at once.
It works like this:
DB (tier 1) ---> Server application (tier 2) --> Client application
(tier 3)
So the ROP objects exist only on tier 3 (which might be a J2EE app,
Swing client application, etc) and the regular server objects on tier
2. There is no cross over: when you commit in tier 3, the corresponding
objects appear on tier 2. The two types of entity classes actually are
in different packages so they are quite separate to each other.
Normally the link between tier 2 and tier 3 is some sort of network
connection: Cayenne uses the Hessian library to serialise objects (even
objects which aren't serialisable!) so they can be transported easily
over a connection. In my case I use Jetty.
Now it is possible to run tier 2 and tier 3 within the same
application, faking the connection between the two. In fact one of my
developers is doing that right now in order to make running test suites
easier in a combined application rather than as server/client.
For those people unfamiliar with this 3 tier structure, an advantage is
that the third tier doesn't talk to the database directly. That means
that the server can implement any sort of business logic you want. For
example, the client app might save a new record, but the server
application has the listeners in place to create audit trail records,
perform additional server-side validation, etc. Not only do you move
processing load off the server, but you don't have to trust the client
application with a write password to the whole database. This applies
whether you are running J2EE, desktop applications, or whatever.
I think that Andrey has considered merging the ROP object classes with
the regular server entity classes, and that would make sharing code
(eg. validation) much easier between the two. However that hasn't
happened yet and the object classes, and the context class is quite
different. I am not sure whether Andrey is still working on that code
or how hard it might be.
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Aristedes Maniatis
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