Database Reference
In-Depth Information
Our short walk through Proxy and other related patterns can be summarized as follows:
• Most of the patterns discussed in the preceding sections are from OOP and tradi-
tional components design practices. Their area of application lies mostly within
the component/service architectural layer, and they are governed by the principles
that are not always in accordance with the SOA design principles. Inheritance is
quite opposite to Loose Coupling.
• The preceding fact must not discourage us from learning and adapting these pat-
terns to work in an ESB framework. Contradiction of principles is a regular oc-
currence, even the SOA principles are not always friendly to each other. Besides,
OOP and traditional integration are major contributors to SOA.
• Proxy is a service governance pattern that is actively used in more complex
design patterns. Its primary role is to decouple service consumers and service pro-
viders. Generally, it is either an object wrapper or a remote placeholder for the
object that presents the same interface to its subject.
• Adapter is a wrapper as well, but it offers a different subject's interface (adapted
to consumer). This allows dissimilar objects to communicate. Transformation
(model or format) is one of the functionalities of an Adapter. Protocol bridging
for disparate protocols is another functionality.
• The Decorator pattern enhances an existing interface by adding new method(s).
• Facade implements a simplified and more abstract interface suitable for invoca-
tion by clients with different requirements, as it introduces a consolidated view of
enterprise objects. Abstract Factory has a similar purpose.
• In order to guarantee smooth and reasonably painless service evolution, you must
plan two placeholders for the Façade pattern implementation in a new service
design: one between the contract and service logic and another between the ser-
vice logic and the underlying resources.
• Abstract Factory can also abstract and wrap dissimilar interfaces together with
Adapter patterns, effectively introducing Adapter Factory with the main purpose
of dispatching a request to the particular interface.
Now, it will be interesting to see how these EAI patterns can be implemented on an Oracle
realization of Service Bus.
Implementing a basic Proxy on OSB
Although we have no intention (and primarily, bookspace) to supply you with detailed
step-by-step OSB tutorials, some guidelines to create the basic OSB resources and Proxy
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