What is an ESB?
The ESB is seen as the next generation of EAI - better and without the vendor-lockin characteristics of old.
As with EAI systems, ESB is not about business logic that is left to higher levels. It is about infrastructure logic.
Although there are many different definitions of what constitutes an ESB, what everyone agrees on now is that an ESB is part of an SOA infrastructure. However, SOA is not simply a technology or a product: it's a style of design, with many aspects (such as architectural, methodological and organisational) unrelated to the actual technology. But obviously at some point it becomes necessary to map the abstract SOA to a concrete implementation and that's where the ESB comes in to play.
Traditional EAI stacks consist of:
Business Process Monitoring,
Integrated Development Environment,
Human Workflow User Interface,
Business Process Management,
Connectors,
Transaction Manager,
Security, Application Container,
Messaging Service,
Metadata Repository,
Naming and Directory Service,
Distributed Computing Architecture.
because of their heritage, ESBs typically come with a few assumptions that are not inherent to SOA:
- Java specific.
- Run-time message mediator.
- Message translation.
- Security model translation.
Other capabilities that an ESB provides include:
- Process orchestration, typically via WS-BPEL.
- Protocol translation.
- Adapters.
- Change management (hot deployment, versioning, lifecycle management).
- Quality of service (transactions, failover).
- Quality of protection (message encryption, security).
- Management.