Information Technology Reference
In-Depth Information
Service
orchestration-
based custom
applications
Portals
Reliable asynchronous secure messaging
Service
interface
Service
container
Distributed
query engine
Web
services
JMS/
J2EE
MQ
gateway
Adapters
WebSphere,
.NET apps
Java apps
Mainframe
and legacy
apps
Business
data sources
Enterprise
applications
Multiplatform
support
FIGURE 9.1
Enterprise Service Bus (ESB) linking disparate systems and computing environments.
The ESB distributed processing infrastructure is aware of applications and
services and uses content-based routing facilities to make informed deci-
sions about how to communicate with them. In essence, the ESB provides
docking stations
for hosting services that can be assembled and orchestrated
and are available for use to any other service on the bus. Once a service is
deployed into a service container, it becomes an integral part of the ESB and
can be used by any application or service connected to it. The service con-
tainer hosts, manages, and dynamically deploys services and binds them to
external resources, for example, data sources, enterprise, and multiplatform
applications, such as shown in Figure 9.1.
The distributed nature of the ESB container model allows individual
event-driven services to be plugged into the ESB backbone on an as-needed
basis. It allows them to be highly decentralized and work together in a
highly distributed fashion, while they are scaled independently from one
another. Applications running on different platforms are abstractly decou-
pled from each other and can be connected together through the bus as logi-
cal endpoints that are exposed as event-driven services. The WS-Notification
family of specifications will bring the publish/subscribe functionality to
ESB-focused current incarnations of Web Service standards (see Chapter 8,
Section 8.1, “Web Service Standards”).
To successfully build and deploy a distributed SOA, there are five design/
deployment and management aspects that need to be addressed first:
1.
Service analysis and design
: A service development methodology
should be used to enable service-oriented development and the
reuse of existing applications and resources.
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