Enterprise System Integration. Lecture 10: Implementing Process-Centric Composite Services in BPEL

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1 MTAT Enterprise System Integration Lecture 10: Implementing Process-Centric Composite Services in BPEL Marlon Dumas marlon. dumas ät ut. ee

2 Questions about reading material Week 8: Zimmermann, Doubrovski, Grundler & Hogg: Service-oriented architecture and business process choreography in an order management scenario: rationale, concepts, lessons learned. Which business processes needed to be automated in this project? What types of activities appeared in these business processes? What types of customers s needed to interact with these processes? What were the perceived benefits of using an SOA? What technology was used to implement these processes and why? Week 9: Szabelak & Topinski: The Tao of Service-Oriented Architecture Governance. What are the phases in the proposed SOA roadmap? What are the key elements of the proposed approach to facilitate minimize SOA project interdependencies? 2

3 SOA Lifecycle and Roles Solution Architect Week 6 Week 7& 8 Service & Process Design Service & Process Analysis Service & Process Implementation Developer Weeks 10 & 11 Testing & Deployment Tester Business Analyst Opportunity & Issue Identification Operation & Monitoring Administrator 3

4 Breaking Silos With Process-Centric Composite Services Business Logic Business Logic Business Logic Business Logic Manufacture Sales Logistics Finance System Silos Integrated Systems 4 4/ 112

5 Web Service Technology Stack Orchestration BPEL Description WSDL, XML Schema, WS-Policy Advertisement UDDI Messaging WS-Addressing, WS-ReliableMessaging, WS-Security... SOAP Transport HTTP, SMTP, FTP Format XML 5

6 BPEL Business Process Execution Language (also called WS-BPEL, BPEL4WS) Language g specifically designed to implement process-centric services Version 1.0 & 1.11 proposed by major vendors; version 2.0 is an OASIS standard XML Syntax, but vendors provide visual notations, e.g. Oracle BPEL, IBM WebSphere (demo at the end of lecture) 6

7 Why BPEL? One could implement process-centric services in Java or C# But instead of hard-coding rules regarding important business processes in application code we take this information out of the application code and put it under the control of a BPM system (e.g. based on BPEL). Facilitates Business Process: Modification Reconfiguration Optimization Graphical tools can be used to visualize process flow. 7

8 BPEL Overview... employeedb HR Process- Centric Service (BPEL).... bank... R. Khalaf et al. courier 8

9 BPEL Overview (cont.) R. Khalaf et al. 9

10 BPEL Features At its core, BPEL is an imperative programming language: scoped variables assignment sequence while if then else exception handlers (throw / catch) 10

11 BPEL Features (cont.) BPEL offers few features specific to WS programming: XML variable typing (XML Schema or WSDL) expressions can be written in XPath/XSL; Message send and receive e actions; parallelism and synchronisation; Race conditions (e.g. a message competing with a timer) transaction compensation; multiple sequential or concurrent executions of a block (foreach) 11

12 BPEL Basic Activities Do a blocking wait for a Generate a fault from inside receive throw matching message to arrive the business process Send a message in reply to a reply formerly received message Invoke a one-way or requestresponse invoke operation Update the values of variables or partner links with assign new data Immediately terminate exit execution of a business process instance wait Wait for a given time period or until a certain time has passed Invoke compensation on an compensate inner scope that has already completed D. Koenig 12

13 BPEL Structured Activities Contained activities flow are executed in parallel, partially ordered through control links sequence Contained activities are performed sequentially in lexical order while Contained activity is repeated while a predicate holds repeatuntil Contained activity is repeated until a predicate holds Block and wait for a suitable pick message to arrive (or time out) Contained activity is performed multiple times foreach sequentially or concurrently Select exactly one branch of activity from a set of choices (also called switch in BPEL if then else 1.1) Associate contained activity with its own local l variables, scope fault handlers, compensation handler, and event handlers D. Koenig 13

14 Nesting of Activities <sequence> <receive.../> <flow> <sequence> <invoke.../> <while... > <assign>...</assign> </while> </sequence> <sequence> <receive.../> <invoke... > </sequence> </flow> <reply> </sequence> receive sequence invoke while assign sequence flow sequence receive invoke reply D. Koenig 14

15 BPEL Code Snippet 1 <process > <sequence> <receive partner= HR porttype= tns:processpt tns:processpt operation= op1 op1 variable=... createinstance= yes /> <invoke partner= employeedb porttype= operation = op2" inputvariable= outputvariable=.../> <invoke partner= bank porttype= operation= op3" inputvariable= outputvariable= /> <invoke partner= courier porttype= operation= op4" inputvariable= outputvariable= /> <receive partner= courier porttype= tns:processpt operation= op5" variable= /> <reply partner= HR porttype= tns:processpt operation= op1 variable = /> </sequence> </process> 15

16 BPEL Code Snippet 2 <flow> <sequence> <invoke name="inv1" partnerlink="pl1" porttype="pt1" operation="op1 inputvariable="var1"/> <receive name="rcv1" partnerlink="pl2" porttype="pt2" operation="op2 variable="var2"/> </sequence> <sequence> <receive name="rcv2" partnerlink="pl1 porttype="pt2" t2" operation="op2 variable="var3"/> <receive name="rcv3" partnerlink="pl3 porttype="pt3" p operation="op2 p variable="var4"/> </sequence> </flow> 16

17 Scopes and Handlers Scope Local variables Local partner links Local correlation sets Set of activities (basic or structured) Handlers Event handlers Message events or timer events (deadline or duration) Fault handlers Dealing with different exceptional situations (internal faults) Compensation handler Undoing persisted effects of already completed activities Termination handler Dealing with forced scope termination (external faults) variables partner links scope correlation sets... event handlers fault fault handlers handler compensation handler termination handler D. Koenig 17

18 Fault Handling and Compensation Process sequence fault handler scope scope notify manager charge credit card compensation handler refund customer ship goods fault handler rethrow compensate D. Koenig 18 18

BPEL and WSDL Every BPEL process definition is exposed as a web service whose interface is defined in WSDL BPEL only depends on the abstract part of a WSDL interface definition

19 BPEL and WSDL Every BPEL process definition is exposed as a web service whose interface is defined in WSDL BPEL only depends on the abstract part of a WSDL interface definition (not on the binding ) WSDL / XML Schema are used to describe variable types in a BPEL process definition WSDL Loan Approval PortType Loan Approval Process receive reply Web Service 19

20 BPEL and WSDL (cont.) In addition to providing a service, a BPEL process definition consumes other services The interfaces of consumed services are defined in WSDL Interfaces exposed by the BPEL process Interfaces consumed by the BPEL process WSDL Loan Approval PortType Loan Approval Process receive reply invoke Financial Institution s Web Service (Loan Approver) Web Service Web Service 20

21 BPEL and WSDL (cont.) When using asynchronous interactions, a BPEL process may need to treat its caller as a service itself with its own WSDL Service A Service P Service B receive receive invoke invoke invoke A s WSDL P s WSDL B s WSDL Partner Link Type Partner Link Type 21

22 BPEL and WSDL (cont.) 22

23 BPEL and WSDL (cont.) WSDL XSD WSDL XSD WSDL XSD WSDL XSD WSDL XSD WSDL XSD 23

24 BPEL Partner Link Definition WSDL code snippet: <porttype name= salespt"> <operation name= order"> <porttype name= customerpt"> <operation name= orderresponse"> <partnerlinktype name="salesplt"> <role name= sales"> <porttype name= salespt"/> </role> <role name= customer"> <porttype name= customerpt"/> </role> </partnerlinktype> BPEL code snippet: <partnerlinks> <partnerlink name="salespl myrole= sales partnerrole= customer" partnerlinktype="salesplt"/> 24

25 Correlation in BPEL Synchronous interactions are not always and option in process-centric processes because: When an instance of a process-centric ti service is created, its execution may last for days, weeks or even months Process-centric service definitions need not follow request/response interaction patterns Need to use asynchronous interactions This in turns require correlation 25

26 Correlation in BPEL (cont.) Two correlation methods are supported: The easy way: Use WS-Adressing headers in all SOAP messages Every message has a messageid A message may refer to a previous message through a relatesto header Requires that all services use SOAP and WS- Addressing Not applicable in some advanced scenarios The hard way: Correlation sets 26

27 BPEL Correlation Sets R. Khalaf 27

28 BPEL Correlation Sets (snippets) WSDL snippet: <bpws:property name="employeeid" type="xsd:long"/> <bpws:propertyalias tali propertyname="tns:emplyeeid" tn messagetype="tns:hrpensionrqstmsg" R tm " part="employeerecord" query="/employeerecord/employeeid"/> BPEL snippet: <process > <partnerlinks> </partnerlinks> <variables> </variables> <correlationsets> <correlationset name="employeenum" properties="tns:employeeid"/> </correlationsets> <sequence> <receive partner= HR porttype= tns:processpt operation= processpension variable= request createinstance= yes > <correlationsets> <correlations set= employeenum initiate= yes /></correlationsets> </receive>.. <receive partner= HR porttype= tns:processpt operation= complete variable = completioninfo > <correlationsets> <correlations set= employeenum /></correlationsets> </receive> </sequence> </process> 28

29 Human Tasks Executable Business Process (BPEL) A1 A2 A3 Human Task Management Service A4 Service A1 Service A2 Service A3 Service A4 Service Bus / Container App1: COBOL App2: PL1 App3: Java App4: C# 29

30 References and Acknowledgment This lecture material is based on: C. Ouyang, W.M.P. van der Aalst, M. Dumas, A.H.M. ter Hofstede and M. La Rosa. Service-Oriented Processes: An Introduction to BPEL. In "Semantic Web Services: Theory, Tools and Applications". Idea Group, March R. Khalaf et al.: The Business Process Execution Language for Web Services. Chapter 13 of Process-Aware Information Systems, John Wiley & Sons, 2005 Some slides are taken from a presentation Introduction to BPEL by Dieter König, IBM Reading of the week : Week 10 (video presentation). D. Syer: Introducing Spring Batch Processing. QCon London

MTAT Enterprise System Integration. Lecture 10. Process-Centric Services: Design & Implementation

MTAT Enterprise System Integration. Lecture 10. Process-Centric Services: Design & Implementation MTAT.03.229 Enterprise System Integration Lecture 10. Process-Centric Services: Design & Implementation Marlon Dumas marlon. dumas ät ut. ee SOA Lifecycle Solution Architect Service & Process Design Service