Brian,
"Is that all it takes to create an SCA compliant application?"
If I interpret that correctly, you're expressing surprise that there
doesn't seem to be much to writing SCA applications. If that's correct,
then in one important sense, SCA is structured in the right way.
SCA is designed to keep the coding of components simple - the principle
is that you don't write your code "for SCA", you "just write code".
SCA, like Spring, aims to keep middleware APIs and middleware structures
out of your code. The code concentrates on the business problem at hand
and simply invokes business interfaces when needing to get at services
provided by other components. In Java, those business interfaces simply
arrive in your component code through injection - they are there when
you need them.
The SCA composite files then describe metadata about your component and
the other components & services which it uses. All the "messy stuff"
about the set of components that are used to build your solution and the
way in which they are connected (communication protocols, endpoint
addresses, infrastructure stuff like Security, etc) are placed into the
SCA composite files and are used by SCA to generate the right proxies to
inject into your code when it runs.
You are right in that it does function in a way similar to Spring
(indeed, SCA + Spring is a good combination). The stuff that SCA
provides that goes beyond Spring is:
- it deals with systems built using more than one language, not just
Java (so you can mix PHP, Java, C++, BPEL....)
- it deals with distributed systems, where different parts run on
different machines on a network
- it deals with the metadata needed to describe communication protocols
and infrastructure services in a consistent way
I hope this explanation helps,
Yours, Mike.
Brian O'Neill wrote:
All,
Excuse the ignorance, but I'm trying to understand the benefits of
designing applications using SCA. From the sample applications in
Tuscany, it appears as though Tuscany functions much like Spring; it
provides a means to map logical services to their implementations
(dependency injection), and then adds a layer to compose services on top
of that.
The only SCA specific files I see in the samples are the composition
files. (e.g. Calculator.composite) Thus, it leads to the question, is
that all it takes to create a "SCA-compliant" application?
-brian
--------------------
Brian O'Neill
Technical Architect, Gestalt LLC
mobile: 215.588.6024
http://weblogs.java.net/blog/boneill42/
<http://weblogs.java.net/blog/boneill42/>
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