Hi Dave,
Good to see that you liked Cayenne. Some comments in addition to what
Ari said...
On Mar 1, 2009, at 1:38 PM, Dave Lamy wrote:
So Question #1:
What pitfalls/concerns would you voice regarding a completely
programmatic
Configuration/DataMap buildup? The plan is for the entire cayenne
model,
data nodes and all, to be built up in code during system init (hot
model
deploys are for another day).
This can be done, although as Ari said, this may require some work.
I've done it in the past though... Such project is fairly bearable.
Hot (re)deploys are also possible.
Now for the more interesting part. The goal is for this meta model
to be
definable/relatable across data sources, even to the extent that the
source
is not an RDBMS. A great initial example is our Alfresco integration:
users can define data classes that should be stored in Alfresco,
content +
meta. Those classes could then be related to a class that is stored
in our
internal, Cayenne-managed DB. FKs would be stored across the
sources for
"joins", etc. The data source would be defined in our meta config
in such a
way that the various find/save service methods are exposed in a
uniform
way. In my dreamland I could search for a Cayenne-managed entity
("Person")
via a nested property ("pictures.mimeType") where Picture was an
Alfresco-managed entity and mimeType was a property defined/stored
there,
but that is clearly a challenge without DB joins..
Relating across different persistent engines can be tough. Relating
between different DataNodes in Cayenne is possible with some
limitations. You can store / update objects across DataNodes; you can
fetch relationships; you can perform SelectQueries with qualifier
crossing such relationships only if it does not require a SQL join
across DBs. I.e. a select on an FK will work; a select on a property
of a related object will not.
So Question #2:
Is it possible to work with/customize Cayenne in such a way that I
could
make use of many of the ORM concepts (dirty-object management,
caching, etc)
but inject code in the correct places to do customized find/persist
routines? What are the current limitations of cross-DataNode
cayenne model
support? The alternative I suppose would be for us to write a layer
above
Cayenne that delegated down to the appropriate data source manager
(CayenneManager vs AlfrescoManager or whatever) but that idea isn't
exactly
appealing..
Don't see an easy way to do things transparently for a mix of Cayenne/
Alfresco objects via an ObjectContext. You may investigate custom
queries, but I am with Ari on that - too much work to do it right. So
yeah, something on top of both may be needed.
Andrus
