Am 07.08.2008 um 18:09 schrieb "Stuart McCulloch" <[EMAIL PROTECTED]
>:
2008/8/7 Jackson, Bruce <[EMAIL PROTECTED]>
Its not exactly a legacy situation. The problem I have is one
that's shared
with many object persistence frameworks that would naturally
provide that
capability as a service in an OSGi environment.
In my case, the persistence model is based on the ability of any
bundle to
declare an interface which is suitably annotated, and which the
persistence
service will automatically construct suitable tables, views etc
based on the
interface methods, arguments and annotations. An object factory in
the
provider then generates a "real" object usable in the caller
bundle, and
whose methods are interpreted by a dynamic proxy into calls to the
persistence layer.
The problem comes when you wish to extract information from the
persistence
service. How do you recreate the stored object when the interface
which was
used to create the dynamic proxy is not in the persistence layer's
bundle?
one possible solution that would work with all the current
frameworks is to
use a service to get the interface class - based on something unique
in the
persisted object like the interface name or serialization id
client bundles would register service implementations, which return
any
interface class(es) they know of that match the request. The
persistence
bundle can then iterate over the available services until it finds
one that
can supply the necessary runtime class (or it could use filters to
avoid
iterating)
alternatively... client bundles could register services to recreate
actual
objects based on given data / schema.
a lot of the classloading issues in OSGi can disappear when you use
services
to delegate tasks to the bundles that have the required knowledge.
The hard
part is deciding what to use services for, and what functionality to
push
into which bundle - but you can often use standard OO techniques
like CRC
cards to help brainstorm ideas
imho, services are the best kept secret of OSGi...
+1
regards,
Karl
On 07/08/2008 15:31, "Richard S. Hall" <[EMAIL PROTECTED]> wrote:
Jackson, Bruce wrote:
Does Felix support anything that carries out a similar function to
buddy
class loading in Equinox?
I'm aware of the DynamicImport-Package, but that rather supposes
that the
bundle who declares this knows the bundles that it needs as
"helpers" to
load classes.
Sorry, no, Felix does not support any such option. And you are right,
dynamic imports are probably not exactly what you want either.
Currently, it is possible that the spec will eventually define
something
like this, but currently there is nothing. However, this should
likely
only be used in legacy situations, is that your situation?
-> richard
--
Cheers, Stuart
