企业总线Enterprise Service Bus
1、why ESB
当企业部署了很多web服务后，如何组织好这些服务，如何利用这些服务向客户提供服务是一个必须解决的问题。
As organizations expose more and more functions as services, it is vitally important that this infrastructure should support the management of SOA on an enterprise scale.
2、定义
An ESB provides an infrastructure that removes any direct connection between
service consumers and providers.
The primary driver for an ESB, however, is that it increases decoupling between
service consumers and providers.
3、优点
Decoupling the consumer’s view of a service from the actual implementation
greatly increases the flexibility of the architecture. It allows the substitution of one
service provider for another (for example, because another provider offers the
same services for lower cost or with higher standards) without the consumer
being aware of the change or without the need to alter the architecture to support
the substitution.
4、现状
Note that no single product currently provides strong support in all of the
capabilities that we have defined(注：企业总线是一个很好的概念，但是需要很多产品的支持才能实现). If the aim is to build a fully functional ESB that addresses all the capabilities, then you need to use multiple products in
combination.
5、支持ESB的产品
WebSphere Business Integration Server Foundation 5,1 is not discussed,
because it is an extension of WebSphere Application Server with additional
components to support business integration.
Both WebSphere Application Server V6 and WebSphere Business Integration
Message Broker V5 are suitable products for building an ESB.
WebSphere Application Server as an ESB
优点：对Web Service提供了良好的支持
缺点：消息处理能力较弱
Building an ESB that is based entirely on WebSphere Application Server is an
option when Web services support is critical and the service provider and
consumer environment is predominantly built on J2EE. WebSphere Application
Server is most suitable for implementing ESBs that are based on Web services
standards. It also provides facilities to integrate services that are offered via
enterprise application integration messaging and other sources. However, if
integration with these non-Web service standards-based services is a major
requirement for the ESB, then you should consider WebSphere Application
Server in combination with products that provide more sophisticated support,
such as WebSphere Business Integration Message Broker.
Additionally, if the ESB needs to support high volume and complex data
transformations, routing decisions and data validation, then again, you should
consider it in combination with products that provide more sophisticated support
for this, again, such as WebSphere Business Integration Message Broker.
WebSphere Business Integration Message Broker as an ESB
优点：消息处理能力强
缺点：对Web Service支持的不太好
Building an ESB that is based entirely on WebSphere Business Integration
Message Broker is an option when Web services support is not critical and
quality-of-service requirements demand the use of mature middleware.
WebSphere Business Integration Message Broker V5 can support all the
minimum ESB capabilities that we have defined. However, in comparison with
WebSphere Application Server, it lacks the sophistication of Web services
support that might be required in an ESB implementation which makes extensive
use of these standards.
WBI/SF 速度可能会快一点
MB 的吞吐率比较高
