An Enterprise Service Bus (ESB) is the product of the combination of traditional middleware technology and XML technology, Web service etc. ESB provides the most basic connection hub in network, which is necessary to build enterprise nervous system. ESB has changed the traditional software architecture, compared with the traditional middleware products can provide more low-cost solution. At the same time it also can eliminate the technical differences between different applications, make different application server coordination operation,to achieve the communication and integration between different services.

From the functional perspective, ESB provides the processing mode of event-driven and document oriented, and distributed operation management mechanism.It supports routing and filtering based on content, with the transmission capacity of the complex data, and can provide a series of standard interface.

The five basic functions of ESB:

1) MetaData management services: provide the service registration naming and addressing management function in the range of the bus.

2) transmission service: ensure proper delivery the message between business process which through the enterprise bus interconnection, the transmission also includes basic routing function.

3) Intermediary: provide location transparency of service routing and location services; different message passing form; transmission protocol supports the widely used.

4) a variety of service integration mode: such as JCA, Web, Messaging, Adaptor etc..

5) support services and event management: recording, measuring and monitoring data of the service invocation; provide event detection, triggering and distribution functions.

Eight extended function of ESB:

1) metadata management for services: he must know both ends of his intermediary, as a service request and the request for service requirements, and the service's providers and the description of service which is provided by him;

2) Mediation: it must have a mechanism to complete intermediary role, such as protocol conversion;

3) communication: service publishing, subscription, response request, synchronous and asynchronous message, routing and addressing, etc.;

4) integrated: legacy system adapter, service scheduling and mapping, protocol conversion, data transformation, enterprise application integration middleware continuous, etc..

5) service interaction: service interface definition, service implementation replacement, service message model, service catalogue and discovery, etc..

6) services security: authentication and authorization, non-repudiation and confidentiality, safety standards support, etc.;

7) service quality: transaction, service deliverables, etc.;

8) service level: performance, availability etc..The two function is most often mentioned in ESB is the message transformation and message routing.

ESB Architecture

ESB is a modular and component based architecture. It assumes that services are generally autonomous and availability of a service at a certain moment of time cannot be guaranteed. Therefore messages need to be routed consequently through the message bus for buffering (message queuing) to allow inspection and enhancement of content as well as filtering, correction and rerouting of message flow.

ESB application features

Large-scale distributed enterprise applications needs a middleware technology which is relatively simple and practical to simplify and unity is more and more complicated and tedious enterprise-level information system platform. SOA connect the application of different functional unit through the service definition between good interface and contract connected. The user can be unrestricted reuse software and interconnect all kinds of resources. As long as IT personnel select standard interface packing the old application, construct the new applications into service, then other application system can be very convenient to use these functions service.

Enterprise service bus (ESB) is SOA's message passing architecture and also is the key to support for SOA. ESB is a product of combination of traditional middleware technology and XML technology, Web service etc.,used to achieve accurate, efficient and safe delivery of different enterprise news and information. ESB has changed the traditional software architecture, compared with the traditional middleware products ESB can provide more low-cost solution. At the same time it also can eliminate the technical differences between different applications, allow different services work in coordination, communication and integration between different services. ESB has a very wide application in different fields:

Telecommunications: ESB can be in full support of the telecom industry OSS. ESB is the ideal telecommunications industry application software hosting platform.
Electricity: ESB can be in full support of the power industry EMS. ESB is the ideal SCADA system data exchange platform.
Finance: ESB can be in full support of the concept of business process integration platform between banks and enterprises. ESB is the ideal B2B trading platform.
E-government: ESB can support the application software of e-government business platform, information sharing and exchange platform, analysis and decision support platform.