Is an Enterprise Service Bus (ESB) an important architectural piece to a Service-Oriented Architecture (SOA), or is it just vendor hype in order to sell a particular product such as SOA-in-a-box?
According to IBM.com, an ESB is a flexible connectivity infrastructure for integrating applications and services; it offers a flexible and manageable approach to service-oriented architecture implementation.
With this being said, it is my personal belief that ESBs are an important architectural piece to any SOA. Additionally, generic design patterns have been created around the integration of web services in to ESB regardless of any vendor.
ESB design patterns, according to Philip Hartman, can be classified in to the following categories:
Interaction Patterns: Enable service interaction points to send and/or receive messages from the bus
Mediation Patterns: Enable the altering of message exchanges
Deployment Patterns: Support solution deployment into a federated infrastructure
Examples of Interaction Patterns:
One-Way Message
Synchronous Interaction
Asynchronous Interaction
Asynchronous Interaction with Timeout
Asynchronous Interaction with a Notification Timer
One Request, Multiple Responses
One Request, One of Two Possible Responses
One Request, a Mandatory Response, and an Optional Response
Partial Processing
Multiple Application Interactions
Benefits of the Mediation Pattern:
Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently
Design an intermediary to decouple many peers
Promote the many-to-many relationships between interacting peers to “full object status”
Examples of Interaction Patterns:
Global ESB: Services share a single namespace and all service providers are visible to every service requester across an entire network
Directly Connected ESB: Global service registry that enables independent ESB installations to be visible
Brokered ESB: Bridges services that are reluctant to expose requesters or providers to ESBs in other domains
Federated ESB: Service consumers and providers connect to the master or to a dependent ESB to access services throughout the network
References:
Mediator Design Pattern. (2011). Retrieved 2011, from SourceMaking.com: http://sourcemaking.com/design_patterns/mediator
Hartman, P. (2006, 24 1). ESB Patterns that "Click". Retrieved 2011, from The Art and Science of Being an IT Architect: http://artsciita.blogspot.com/2006/01/esb-patterns-that-click.html
IBM. (2011). WebSphere DataPower XC10 Appliance Version 2.0. Retrieved 2011, from IBM.com: http://publib.boulder.ibm.com/infocenter/wdpxc/v2r0/index.jsp?topic=%2Fcom.ibm.websphere.help.glossary.doc%2Ftopics%2Fglossary.html
Oracle. (2005). 12 Interaction Patterns. Retrieved 2011, from Oracle® BPEL Process Manager Developer's Guide: http://docs.oracle.com/cd/B31017_01/integrate.1013/b28981/interact.htm#BABHHEHD
