Java Reference
In-Depth Information
The precise details of how these intents are accomplished is left up to the distribu-
tion provider.
Qualified intents
Intent values are hierarchical. This is expressed by delimiting the intent value with
the
.
character. For example,
authentication.transport
indicates that the service
should use transport-level authentication. The practical upshot is that a service spec-
ifying
authentication
as an intent may be implemented by a provider that provides
authentication.transport
. But a service specifying
authentication.transport
may not be implemented by a provider only providing
authentication
.
Because the meaning of the intents is well-known, a distribution provider can make its
best attempt at how to achieve them in its underlying implementation. This aids in
decoupling distributed applications, because you can specify the qualities of the
desired remote communication without tying yourself to a particular distribution
technology. If you move your application to a different environment, a different distri-
bution provider may make equally valid but potentially different choices. The
SCA
specification defines many intent values, but the precise details are beyond the scope
of this topic—for more information on
SCA
, visit the
OSOA
consortium website
(
www.osoa.org
).
A service provider specifies intents, and the distribution provider realizes them. Is
this the end of the story? Not exactly. The distribution provider must honor the
requirements of the service provider, but it's free to add any behaviors it feels are
appropriate. These may include default communication protocols, authentication
schemes, and buffering strategies, as shown in figure 15.8.
In summary, intents provide a distribution provider with some flexibility when it
comes to deciding how to distribute a service. Sometimes, though, you know exactly
how you want your service to be made available remotely. In these situations, you need
a mechanism to give specific instructions to the distribution provider. This leads us to
Remote Services configuration properties.
Service
provider
Distribution
provider
Figure 15.8
Service providers and distribution providers can each define intents that are applied
to a service endpoint.
