- You mention in several places about separating away the notion of
specs and stores. In a general sense, I understand what these
are. But,
can you elaborate on how these types are used in the
ConfigurationProvider
and ProductDerivation interfaces?
What I meant was that the ProductDerivation interface has methods and
constants that imply knowledge of what a "spec" is and what a "store"
is: afterSepcificationSet(), TYPE_STORE, etc. These methods and
constants become meaningless when the interface is moved from kernel
to lib, because lib is code that is completely ignorant of what's
built on top of it. OpenJPA kernel understands that there might be
different spec facades built on it, and that there might be different
data stores plugged in, but lib code shouldn't be aware of those
concepts.
Actually, I wouldn't mind moving the
OpenJPAConfiguration.setSpecification() method to the base
Configuration interface and giving lib the notion of a spec, because
that's a sufficiently general idea. But lib certainly shouldn't know
anything about data stores -- that concept is very persistence-
specific. So I believe that at the very least, the TYPE_STORE stuff
has to be moved out of ProductDerivation and into something in the
kernel if ProductDerivation itself moves into lib. As I mentioned in
my original email, it might seem odd to maintain the strict
neutrality of lib code given that it's only used for OpenJPA, but we
do in fact build on that code with some non-persistence-aware Kodo
stuff, and as long as there is a separation of modules within
OpenJPA, I'd like to maintain the meaning of lib-as-neutral vs.
kernel-as-persistence-aware.
Now that we need to return a ConfigurationProvider, would you
expect that we just new up a ConfigurationProviderImpl and then
just call
across to the "load" methods on the implementation? Since we
want to keep
the ProductDerivations stateless, I'm not sure how else you were
expecting
to create a ConfigurationProvider to return on these "load" methods.
I would expect the ProductDerivation itself to do most of the load
work and to populate a new ConfigurationProvider with the parsed
state. The ProductDerivation itself would remain stateless, but
would contain the load logic. We can probably have just one
ConfigurationProviderImpl that will work for most derivations (i.e.
ConfigurationProviderImpl will probably not have to be JPA-specific
anymore, and can move into lib's conf package or somewhere where it
can be used by JDO, etc as well). I bet a slight rework of
MapConfigurationProvider would do the trick.
- Now that ConfigurationProvider is bare, the
ConfigurationTestConfigurationProvider doesn't have much
function. I'll
need to take a look to see if this is even required any longer.
Yeah, I'm sure tests will need updating.
- Can you shed a bit more light on the Configurations class? It
doesn't implement nor extend any interfaces or classes, but it
seems to
provide many of the same methods as ConfigurationProvider, but as
statics.
And, it's dependent on having a Provider. Can you explain the
relationship
of this class in the bigger picture and how you think it might be
affected
by thes changes?
It's a utility class. Aside from the low-level utils it provides,
it's mainly there so that its static configuration methods can be
invoked without worrying about what services the system is configured
with. Configurations does the work of looking up the right
ConfigurationProvider using the services framework and applying it.
Otherwise, each component that used a ConfigurationProvider would
have to invoke the Services utilities itself to figure out which
ConfigurationProvider to use.
When ProductDerivation takes over, Configurations will change to use
ProductDerivations instead, and will subsume the functionality of
kernel's conf.ProductDerivations utility class.
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