Databases Reference
In-Depth Information
When to use the Mediator
Because the Mediator runs within an SCA Assembly, it has the most efficient
bindings to other SCA Assembly components, specifically the BPEL engine. This lets
us focus on using the Mediator to provide service virtualization services within SCA
assemblies. The Mediator enables the virtualization of inputs and outputs within an
SCA Assembly. This leads us to four key uses of the Mediator within SCA.
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Routing between components in an SCA Assembly
Validation of incoming messages into an SCA Assembly
Transformation of data from one format to another within an SCA Assembly
Filtering to allow selection of components to invoke based on
message content
The Mediator is an integral part of SCA Assemblies and should be used to adapt
SCA Assembly formats to the canonical message formats, which we will talk about
later in this chapter.
When to use Oracle Service Bus
The Oracle Service Bus runs in a separate JVM to the other SOA Suite components
and so there is a cost associated with invoking SOA Suite components in terms of
additional inter-process communication and hence time. However, the OSB has
some very powerful capabilities that make it well suited to be the enterprise strength
Service Bus for a more general enterprise-wide virtualisation role. As it is separate
from the other components, it is easy to deploy separately and use as an independent
Service Bus.
The Service Bus can be used to virtualize external services, where external may mean
outside the company but also includes non-SCA services. OSB makes it very easy for
operators to modify service endpoint details at runtime, making it very flexible in
managing change.
The Service Bus goes beyond routing and transformation by providing the ability
to throttle services, restricting the number of invocations they receive. This can be
valuable in enforcing client contracts and ensuring that services are not swamped
by more requests than they can handle.
