BPEL

BPEL 

BPEL is the XML Based language used for composition, orchestration, and coordination of web services. It provides a  rich vocabulary for expressing the behavior of business processes.

BPEL Process Manager – provides a framework for easily  designing, managing

and deploying the BPEL processes.

Strengths of BPEL 

•Orchestrates services

•Designed for long running processes

•Built-in support for asynchronous interaction

•Fault handling and compensating transactions

•Extensible

•Parallel flows

•Conditional branching
 

Business Process Orchestration   

–Orchestration : Combining the Individual services into a single Composite service.

BPEL Process 

 

Partner Links 

•Interaction between a process and partner is achieved via partner links.

•Used to invoke operations on other web services

•receive invocations from clients or other web services

•Partners

•Service Consumer

•Service Provider

•Each BPEL process has at least one Partner Link

Basic Programming Constructs of BPEL

•<receive>        -   wait for a client to make a request

•<reply>            -    generate a response

•<assign>         -    manipulate data variables

•<invoke>         -    invoke other web service

•<throw>           -    raise a fault or exception

•<wait>         -   a short period of time

•<terminate>  -    end the entire process  

Structured Activities
 

•While: For implementing loops

•Switch: Construct for implementing conditional branches

•Flow: For implementing branches that execute in parallel

•FlowN: For implementing a dynamic number of parallel branches

Messaging Activities
 

•Receive

•Invoke

•Reply 

 

Messaging Activities  

Usage  of the commands depends on whether the message is

-Synchronous / Asynchronous

-Consumer / Provider

 

Synchronous messaging 

-BPEL process will wait for a reply before moving on to the next activity. 

Asynchronous Messaging

–once the caller has sent the request, the send operation will return immediately, and the BPEL process may then continue with additional activities until it is ready to receive the reply.

 

One Way Messaging

–A variation of asynchronous messaging is one way messaging (also known as fire and forget).

– This involves a single message being sent from the calling process, with no response being returned.

 

Basic BPEL process

This BPEL process receives a message and sends it back to the sender. 

Will tell you more about BPEL in future posts.