Hi Nicole,
Comments inline...
On Aug 21, 2006, at 10:15 AM, <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
wrote:
Hi Joel and other OSGi interested guys,
What is the role of OSGi in SCA?
I see several roles of OSGi in SCA:
1) OSGi Binding and Reference:
a)
A SCA application can access an OSGi application running outside of
the SCA container via a reference/external service.
Yes, this would be one of the capabilities
b)
A Service Component could be exposed as OSGi Component, similar to
EJBs
as described in http://www.osoa.org/display/Main/EJB+Integration
+White+Paper
That's from my understanding what your implementation is supposed
to do?
Yes, it should do this as well
2) OSGi implementation type
If the SCA container provides an OSGi implementation type, it would
be possible
to deploy existing OSGi applications/bundles in the SCA container
and use them
like SCA components (with all advantages).
I think this an interesting use case, particularly if the
implementation type would be a composite. I'm not sure about atomic
components since OSGi services are more transient in nature. Joel,
what do you think?
3) Use OSGi as underlying technology for a SCA container
OSGi could be the base for a SCA container and could provide
implementation types for EJB, Spring, BPEL etc. OSGi bundles could
run natively in this SCA container.
This was also one of the goals: the Tuscany runtime could be embedded
in an OSGi container such as Equinox. We've started to separate out
the projects so there is a generic OSGi "host integration" project
with the pieces necessary to embed Tuscany in any OSGi container and
an "Equinox project" for specifically running on that OSGi
implementation. We could also run on other OSGi containers.
How does it differ from the role of something like Spring?
Fromy my point of view OSGi and Spring could be implementation
types like 2)
In addition Spring is very useful in an SCA container (to build a
SCA container)
due to its dependency injection feature.
Or, asked in the larger sense, where does SCA fit into the world
of Containers?
In my world SCA is the meta-model on top of existing technologies
which is able
to combine all the different components/services which are hosted
in different containers in a standardized way. It's possible to
combine EJB with OSGi, BPEL with C++, Spring with PHP and whatever
else we can imagine in a standardized way.
New applications should be deployed directly in a SCA container. To
be able to fulfill all requirements it would be helpful having a
SCA container with different implementation types (no need to
restrict the developers to one technology, use always the
technology best suited).
In the Java world, from my point of view, OSGi (due to its dynamic
behaviour and the flexibility) would be the best technology to
build a SCA container.
I'm looking forward to reading your thoughts on this topic.
Yes, I think this is an important feature of SCA, i.e. the ability to
be able to re-use existing technologies. If you would like to jump in
and help, I'm sure Joel, I, and others would appreciate any time/
suggestions you could give.
I believe Joel is working on revising the OSGi projects as we speak
so I'll let him relay what he is up to.
Jim
Best regards
Nicole
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