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Introduction and Advanced Concepts of BPEL
- 1. Introduction and Advanced Concepts of BPEL Denis Weerasiri & Waruna Ranasinghe
- 2. Overview • What is BPEL • WSO2 Business Process Server • Introduction to BPEL • HelloWorld Sample • Advanced Concepts of BPEL • Fault Handling • Compensation Handling • Correlation and Async processes • Extending WSO2 BPS
- 3. What is BPEL • An OASIS standard executable language for business processes • More or less a service composition language • Enables composition of (business) services into business processes • XML based language
- 4. Why Automate Business Processes • Increase Efficiency • No need to worry about the coordination of the process • Improve Responsiveness • Business processes are agile • Improve the process • Adapt to the change of business needs
- 5. Business Process wrt BPEL Business Process is a collection of coordinated service invocations and related activities that produce a result, either within a single organization or across several organizations
- 6. Why BPEL • Agility • No need to worry about low level programming stuff. • Native support for long running processes • Compose larger business processes out of smaller processes and services • Handle message-related and time-related events • Industry standard language for expressing business processes • Leverage common skill set
- 7. Why BPEL • Portability • Managed execution • Monitor the progress of the process • Start, stop, suspend, resume process instance
- 8. WSO2 Business Process Server • Executes business processes written using WS- BPEL standard • Powered by Apache ODE • Provide a web-based management console • Deploy processes • Manage and view business processes • Manage and view process instances • Configure QoS and many more…
- 9. Why WSO2 BPS • WSO2 Carbon Studio – BPEL Editor • Drag and drop process modeler • Native BPEL support • XPath editor • Deploy processes to WSO2 BPS • Support both BPEL4WS 1.1 and WS-BPEL 2.0 • Graphical Management Console to: • Deploy and manage business processes • Manage and monitor process instances • Configure QoS perameters
- 10. Why WSO2 BPS • Process dehydration • Process versioning • Follow open standards – avoid vender lock-in • Support XQuery and Xpath, XSLT • Support BPEL Extensions • Features from WSO2 Carbon
- 11. Want to implement Business Processes? • What you should already know • XML • XML Namespaces • XML Schema • WSDL • XPath • XSLT and XQuery (optional)
- 12. Introduction to BPEL • BPEL Concepts • Activities • Basic Activities • Structured Activities • HelloWorld sample process
- 13. BPEL Concepts
- 14. Partner Links • Defines the “Contact channels” between external world (clients/partner services)
- 15. Partner Links • Associates interfaces (WSDL ports) with roles, using PartnerLinkTypes
- 16. PartnerLinkType • Characterizes the conversational relationship between two services • Define the roles played by each of the services in the conversation <plnk:partnerLinkType name="BuyerSellerLink"> <plnk:role name="Buyer" portType="buy:BuyerPortType" /> <plnk:role name="Seller" portType="sell:SellerPortType" /> </plnk:partnerLinkType>
- 17. PartnerLynkType Buyer Seller Buyer Seller Invoke Invoke Seller Seller Send response to Buyer’s Process Partner Process Partner Callback Service Service Async Sync
- 18. Partner Link • Associates with a partnerLinkType <partnerLinks> <partnerLink name=“BuyerSellerPL” partnerLinkType=“BuyerSellerLink” myRole=“Buyer” partnerRole=“Seller”/> </partnerLinks> • Defines which role should be played by the process itself and the partner service
- 19. Variables and Data Manipulation • Variables • Statically typed(via WSDL Messages, XSD elements and XSD types) • Assigning values to variables • When message is received from a partner • Manipulate variables inside <assign> activity • Require knowledge about XPath, XQuery, XSLT
- 20. Activities in BPEL • Basic Activities • Structured Activities
- 21. Basic Activities • Receive • Compensate • Reply • Catch • Invoke • Throw • Assign • Rethrow • Wait • Exit • Empty
- 22. Receive • Act as the entry point to the business process • Receives messages from an external partner • Associated with • PartnerLink with myRole • WSDL operation • Variable for the incoming message • createInstance="yes" to create a new process instance, otherwise the incoming message will be consumed by the (already running) process instance
- 23. Reply • Sends the response back to the client • Always relates to a “receive” activity • Associated with • Same PartnerLink for the “receive” • Same operation for the “receive” • Variable for the output message
- 24. Invoke • Used to consume partner services • Associated with • PartnerLink with at least a “partnerRole” • WSDL operation of the partner service • Input variable • Output variable, if the operation is request- response
- 25. Assign • Used to manipulate variables
- 26. Initializing Variables • Variables contain a piece of XML • Manipulated using Xpath • XPath is evaluated on XML • The variable should be initialized before copying values to the internal elements.
- 27. What we want myProfile = <profile> <name>Waruna</name> </profile>
- 28. What we got • String variable “name” – “Waruna” • Variable “myProfile” – “” • “myProfile” variable should be initialized before copying the “name” variable into the “name” element of “myProfile” variable • $myProfile/profile/name
- 29. Initialization • myProfile = <profile> <name></name> </profile> • Then copy the “name” into “name” element of the “myProfile” variable. • $myProfile/profile/name
- 30. Activities in BPEL • Basic Activities • Structured Activities
- 31. Structured Activities • Sequence • Flow • While • RepeatUntil • ForEach • If • Pick • Scope
- 32. Sequence • Contained activities will be executed in an ordered manner
- 33. Flow • Execute contained activities in parallel
- 34. Looping • While, RepeatUntil, ForEach • Provides repeated execution of the contained activity
- 35. If • Provides conditional behavior
- 36. Pick • Waits for the occurrence of exactly one event from a set of events. • OnMessage • OnAlarm
- 37. Scope • Group activities into logical scopes • Variables • Partner Links • Fault Handlers and Compensation Handlers
- 40. Advanced Concepts • Fault Handling • Compensation • Correlation and Async processes • Extending WSO2 BPS
- 41. Fault Handling • Exceptional condition that can alter the normal processing of a business process. • Fault need not result in an immediate process ending. • If a fault is not handled, it will lead to unexpected conditions and outcomes. • Handle faults, so that failures lead to predictable outcomes.
- 42. Activities for Handling Faults • Catch • CatchAll • Rethrow • Throw
- 43. Catch/CatchAll • BPEL specific runtime faults • SOAP faults • Standard SOAP faults • Application specific SOAP faults • After catching a fault • Try to correct • Throw a new fault • Rethrow the fault • Reply with a fault message
- 44. Catch/CatchAll • Handle different types of faults in different ways. • Multiple catch statements to catch different types of faults. • CatchAll activity to handle any type of Fault.
- 45. Rethrow • If the current fault handler cannot handle the fault • Propagate the fault to an outer-scoped fault handler • Available only within a fault handler
- 46. Throw • Indicates a problem that a business process flow cannot handle • Can be used any where within the process • Can be thrown • Standard BPEL faults • Custom faults • Variable can be associated to send fault information
- 47. Fault Handlers Attached to Invoke Activity • Handle faults specific to Invoke activity • SOAP faults
- 48. Fault Handlers attached to Scope • Catches faults resulting from activities within a scope.
- 49. Global Fault Handler • Last place for a fault to be captured. • Faults propagate from the inner scopes to the outer scopes
- 50. Fault Types in Invoke Activity • Faults • BPEL standard faults • SOAP faults • Failures • Connection refused • Service not found
- 52. Compensation • Undoing the steps in business process that have been already completed
- 53. Activities for Compensation Handling • compensationHandler – defines the compensation logic per each scope • compensateScope and compensate - used to trigger the compensationHandler.
- 55. Asynchronous Invocation • What Asynchrony is. • Different asynchronous transport protocols eg – JMS, SMTP, XMPP • Modeling asynchronous behavior in WSDLs eg – by two one-way operations
- 56. Asynchronous Invocations in BPELs • Invoke activity to invoke the partner-service • Receive activity to act as the call-back handler • So how these two messages get correlated?
- 57. Message Correlation • Building block for stateful conversations in BPELs • Determine to which conversation a message belongs
- 58. Message Correlation Sets • correlationSet - defines the element(s) in message to act as a unique-id for each message • correlation - handles the message correlation between each conversation
- 60. Extending WSO2 BPS • BPEL extensions • Enable to define new BPEL activities • peopleActivity for BPEL4People • BPEL event listeners • Enables to listen to events fired by BPEL engine • Gather information for BAM • Message exchange interceptors • Enables to intercept through the message exchanges • XPath extensions
- 61. Q&A