Database Reference
In-Depth Information
Most commonly, the Java web container will probably use a servlet as the front controller,
and it is responsible for parsing the header elements and invoking the JAXB mapping to
Java objects to process the SOAP body.
We will discuss UDDI-related protocols as part of contemporary SOA further when we
approach the Service Registry architecture.
Need for the WS-* extensions
There are no drawbacks in the contemporary SOA model. Every single technical element
is mature and proven to be reliable after dozen of years of evolution and improvements.
Actually, it was pretty acceptable from the very beginning, but its broad usage was
severely limited by the initial constraints set by the simplified service interaction model:
synchronous request-response between limited numbers of composition members (usually
two). At the time of the first implementation, it was apparent that a substantial number of
complex real-life requirements needed be addressed by the SOA technology platform to
make it capable of fulfilling its promises; they are as follows:
• There is more than one simple
message exchange pattern
(
MEP
). We can count
one-way MEPs, two-ways, callback MEP types along with all possible types of
acknowledgements (responses), such as mandatory, only on errors, and so on.
• Asynchronous MEPs are equally popular and must be covered by the technology
platform in a common way. The ability to maintain sync-async communication
bridges for complex service interactions was the prerequisite for further SOA pro-
liferation.
• Even synchronous service compositions could be far more complex than the basic
request-response method with all elements of distributed transactions and two-
phase commits requiring a transparent level of transaction coordination.
• Long-running transactions also need common and reliable methods of controlling
process execution with a lot of callbacks and numerous activation-deactivation
phases. First of all, this involves transparent coordination based on the correlation
ID and correlations sets, and the ability to compensate unsuccessful transactions.
• Services must be able to reliably communicate in cases where we have infrastruc-
ture breakdowns or slow responses from other parties.
• Service messages must be equipped with information that is sufficient for sup-
porting complex routings and distributions.
• Services and service registries are extremely vulnerable to security breaches due
to high exposure to potential consumers (implementation of the Discoverability
principle). This issue will be addressed with minimal impact on services intrins-
ic's interoperability.
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