Get documents about "BPEL Business Process Execution Language for Web Services
Document Sample
BPEL: Business Process Execution
Language for Web Services
Dr. Yuhong Yan
NRC-IIT-Fredericton
Internet logic
What is BPEL
• It is positioned to become a standard for Web
service composition.
• a notation for specifying business process
behavior based on Web services.
• a joint specification of IBM, BEA, Microsoft, SAP,
and Siebel
• OASIS ( Organization for the Advancement of
Structured Information Standards e-business
standards) standard.
The description of a workflow
Need Process to satisfy need Need satisfied
Go to coffee shop Make and serve
Order Drink
Satisfy thirst
with coffee Service Thirst
quenched
Buy coffee
machine Install Operate Fill cup Drink
Tangible good + self service
The description of workflow
Loan Request
request.amount request.amount>=1000
<1000
Send to Risk Assessor Send to Approver
risk.level!=low
risk.level=low
Prepare the answer
Reply
BPEL: describe the business logic
• The sequence of the activities (operations in
WSDL)
• The triggering conditions of the activities
• The consequences of executing the activities
• The partners for the external activities
• The composition of Web Services
• The binding to WSDL
Business Process (what) versus WSDL (how)
Business Process: what to do
• Modeled as a sequence of activities Business
• Tools aid to define, monitor, and WSDL Process
manage business processes WSDL
A
WSDL
C B
WSDL: how to execute activities WSDL
• An activity can be an internal or D
WSDL
external Web service (SOAP/WSDL)
E
• A business process can be exposed
for consumption by a client app or
another business process APPLICATION
BPEL Process Model
WSDL Dynamic Partner/
portType Service Selection
A Business Process:
1. Comprises choreography 1 A
elements to define behavior
2. Exposes operations with B
constraints as Web services 2 C
3. Uses other Web services to
do its job D
3 E
Service External
logic Service
How BPEL looks like?
<process name="echoString"
targetNamespace="urn:echo:echoService"
xmlns:tns="urn:echo:echoService"
xmlns="http://schemas.xmlsoap.org/ws/2003/03/business-process/">
<partnerLinks>
<partnerLink name="caller"
partnerLinkType="tns:echoPLT"
myRole="service"/>
</partnerLinks>
<variables>
<variable name="request" messageType="tns:StringMessageType"/>
</variables>
<sequence name="EchoSequence">
<receive partnerLink="caller" portType="tns:echoPT"
operation="echo" variable="request"
createInstance="yes" name="EchoReceive"/>
<reply partnerLink="caller" portType="tns:echoPT"
operation="echo" variable="request" name="EchoReply"/>
</sequence>
</process>
How BPEL looks like?
• <process>: root element of bpel
• <partnerLink>: external partners
• <variables>: variables in the process
• <sequence>: a sequence scope
• <receive>, <reply>: basic activities
BPEL basic activities
• <receive> allows the business process to do a
blocking wait for a matching message to arrive.
• <reply> allows the business process to send a
message in reply to a message that was received
through a <receive>. The combination of a
<receive> and a <reply> forms a request-
response operation for the process.
• <invoke> allows the business process to invoke
a one-way or request-response operation on a
portType offered by a partner.
BPEL basic activities (Cont’d)
• <assign> is used to copy data from one place to
another.
• <throw> generates a fault from inside the
business process.
• <terminate>: terminate the entire service
instance. It is only available in executable
processes.
• <wait> allows you to wait for a given time period
or until a certain time has passed.
• <empty> allows you to insert a “do nothing”
instruction to the process.
Activities in BPEL vs.portType in WSDL
<process name="echoString" <definitions targetNamespace="urn:echo:echoService"
targetNamespace="urn:echo:echoService" xmlns:tns="urn:echo:echoService"
xmlns:tns="urn:echo:echoService" xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-
link/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://schemas.xmlsoap.org/ws/2003/03/busin
ess-process/"> xmlns="http://schemas.xmlsoap.org/wsdl/">
<message name="StringMessageType">
<partnerLinks> <part name="echoString" type="xsd:string"/>
<partnerLink name="caller" </message>
partnerLinkType="tns:echoPLT"
myRole="service"/> <portType name="echoPT">
</partnerLinks> <operation name="echo">
<input message="tns:StringMessageType"/>
<variables> <output message="tns:StringMessageType"/>
<variable name="request" </operation>
messageType="tns:StringMessageType"/> </portType>
</variables> <plnk:partnerLinkType name="echoPLT">
<plnk:role name="service">
<sequence name="EchoSequence"> <plnk:portType name="tns:echoPT"/>
<receive partnerLink="caller" portType="tns:echoPT" </plnk:role>
operation="echo" variable="request" </plnk:partnerLinkType>
createInstance="yes" name="EchoReceive"/>
<reply partnerLink="caller" portType="tns:echoPT" <!-- The service name and the TNS represent my service ID QName -
operation="echo" variable="request" ->
name="EchoReply"/> <service name="echoServiceBP">
</service>
</sequence>
</process> </definitions>
The structure of activities
• <sequence>: an ordered sequence of
steps
• <switch>: “case-statement” approach
• <while>: loop
• <pick>: execute one of several alternative
paths
• <flow>: parallel steps
Partners
• For <invoke>
– Invoke an operation at an external web service
– The external web service is Process partner
• For <receive> and <reply>
– The client sends message to invoke a local
web service
– The client is client partner
• <partnerLinks> : The different parties involved in
the business process
<partnerLinks> in BPEL
<partnerLinks>
<partnerLink name="caller"
partnerLinkType="tns:echoPLT"
myRole="service"/>
</partnerLinks>
<partnerLinkType> in WSDL
<plnk:partnerLinkType name="echoPLT">
<plnk:role name="service">
<plnk:portType name="tns:echoPT"/>
</plnk:role>
</plnk:partnerLinkType>
PartnerLink in BPEL vs.partnerLinkType in
WSDL
<process name="echoString" <definitions targetNamespace="urn:echo:echoService"
targetNamespace="urn:echo:echoService" xmlns:tns="urn:echo:echoService"
xmlns:tns="urn:echo:echoService" xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-
link/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://schemas.xmlsoap.org/ws/2003/03/busin
ess-process/"> xmlns="http://schemas.xmlsoap.org/wsdl/">
<message name="StringMessageType">
<partnerLinks> <part name="echoString" type="xsd:string"/>
<partnerLink name="caller" </message>
partnerLinkType="tns:echoPLT"
myRole="service"/> <portType name="echoPT">
</partnerLinks> <operation name="echo">
<input message="tns:StringMessageType"/>
<variables> <output message="tns:StringMessageType"/>
<variable name="request" </operation>
messageType="tns:StringMessageType"/> </portType>
</variables> <plnk:partnerLinkType name="echoPLT">
<plnk:role name="service">
<sequence name="EchoSequence"> <plnk:portType name="tns:echoPT"/>
<receive partnerLink="caller" portType="tns:echoPT" </plnk:role>
operation="echo" variable="request" </plnk:partnerLinkType>
createInstance="yes" name="EchoReceive"/>
<reply partnerLink="caller" portType="tns:echoPT" <!-- The service name and the TNS represent my service ID QName -
operation="echo" variable="request" ->
name="EchoReply"/> <service name="echoServiceBP">
</service>
</sequence>
</process> </definitions>
<variables>
• Data variables used by activities
– <variable messagetype=“...”>: WSDL message;
– <variable type=“…”>: XML Schema simple
type;
– <variable element=“…”>: XML Schema
element.
• Variables associated with message types can be
specified as input or output variables for invoke,
receive and reply activities.
Variables in BPEL vs.Messages in WSDL
<process name="echoString" <definitions targetNamespace="urn:echo:echoService"
targetNamespace="urn:echo:echoService" xmlns:tns="urn:echo:echoService"
xmlns:tns="urn:echo:echoService" xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-
link/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://schemas.xmlsoap.org/ws/2003/03/busin
ess-process/"> xmlns="http://schemas.xmlsoap.org/wsdl/">
<message name="StringMessageType">
<partnerLinks> <part name="echoString" type="xsd:string"/>
<partnerLink name="caller" </message>
partnerLinkType="tns:echoPLT"
myRole="service"/> <portType name="echoPT">
</partnerLinks> <operation name="echo">
<input message="tns:StringMessageType"/>
<variables> <output message="tns:StringMessageType"/>
<variable name="request" </operation>
messageType="tns:StringMessageType"/> </portType>
</variables> <plnk:partnerLinkType name="echoPLT">
<plnk:role name="service">
<sequence name="EchoSequence"> <plnk:portType name="tns:echoPT"/>
<receive partnerLink="caller" portType="tns:echoPT" </plnk:role>
operation="echo" variable="request" </plnk:partnerLinkType>
createInstance="yes" name="EchoReceive"/>
<reply partnerLink="caller" portType="tns:echoPT" <!-- The service name and the TNS represent my service ID QName -
operation="echo" variable="request" ->
name="EchoReply"/> <service name="echoServiceBP">
</service>
</sequence>
</process> </definitions>
<faultHandlers>
• In response to faults
• Defines the recovery actions when faults occur
• Its sole aim is to undo the partial and
unsuccessful work of a scope in which a fault
has occurred.
EachString: BPEL vs. WSDL
<process name="echoString" <definitions targetNamespace="urn:echo:echoService"
targetNamespace="urn:echo:echoService" xmlns:tns="urn:echo:echoService"
xmlns:tns="urn:echo:echoService" xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-
link/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="http://schemas.xmlsoap.org/ws/2003/03/busin
ess-process/"> xmlns="http://schemas.xmlsoap.org/wsdl/">
<message name="StringMessageType">
<partnerLinks> <part name="echoString" type="xsd:string"/>
<partnerLink name="caller" </message>
partnerLinkType="tns:echoPLT"
myRole="service"/> <portType name="echoPT">
</partnerLinks> <operation name="echo">
<input message="tns:StringMessageType"/>
<variables> <output message="tns:StringMessageType"/>
<variable name="request" </operation>
messageType="tns:StringMessageType"/> </portType>
</variables> <plnk:partnerLinkType name="echoPLT">
<plnk:role name="service">
<sequence name="EchoSequence"> <plnk:portType name="tns:echoPT"/>
<receive partnerLink="caller" portType="tns:echoPT" </plnk:role>
operation="echo" variable="request" </plnk:partnerLinkType>
createInstance="yes" name="EchoReceive"/>
<reply partnerLink="caller" portType="tns:echoPT" <!-- The service name and the TNS represent my service ID QName -
operation="echo" variable="request" ->
name="EchoReply"/> <service name="echoServiceBP">
</service>
</sequence>
</process> </definitions>
Echo Sample
<PartnerLinks> in BEPL
<partnerLinks>
<partnerLink name="caller“
partnerLinkType="tns:echoPLT“ myRole="service"/>
</partnerLinks>
<partnerLinkType> in WSDL
<plnk:partnerLinkType
xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-link/"
name="echoPLT">
<plnk:role name="service">
<plnk:portType name="tns:echoPT"/>
</plnk:role>
</plnk:partnerLinkType>
Activities in BEPL
<sequence name="EchoSequence">
<receive partnerLink="caller" portType="tns:echoPT"
operation="echo" variable="request"
createInstance="yes" name="EchoReceive"/>
<reply partnerLink="caller" portType="tns:echoPT"
operation="echo" variable="request" name="EchoReply"/>
</sequence>
PortType in WSDL
<portType name="echoPT">
<operation name="echo">
<input message="tns:StringMessageType"/>
<output message="tns:StringMessageType"/>
</operation>
</portType>
Simple sample
<partnerLinks> <PartnerLinks> and <Partners> in BEPL
<partnerLink name="caller" partnerLinkType="tns:StockQuotePLT"/>
<partnerLink name="provider" partnerLinkType="tns-utils:StockQuotePLT"/>
</partnerLinks>
<partners>
<partner name="invoker">
<partnerLink name="caller"/>
</partner> another Web Service
<partner name="serviceProvider">
defined in
<partnerLink name="provider"/>
stockquote.wsdl
</partner>
</partners>
Simple: StockQute Sample
<variable name="request" messageType="tns:request"/>
<variable name="response" messageType="tns:response"/>
…
<receive name="receive" partnerLink="caller" portType="tns:StockQuotePT"
operation="gimmeQuote" variable="request"
createInstance="yes"/> Variable,
<reply name="reply" partnerLink="caller" portType="tns:StockQuotePT" Receive and
operation="gimmeQuote" variable="response"/> Reply in BPEL
<message name="request">
<part name="symbol" type="xsd:string"/>
</message>
<message name="response"> Message
<part name="quote" type="xsd:float"/>
</message>
and portType in WSDL
<portType name="StockQuotePT">
<operation name="gimmeQuote">
<input message="tns:request"/>
<output message="tns:response"/>
</operation>
</portType>
Invoke external WSDL
<Invoke> in BEPL
<invoke name="invoke"
partnerLink="provider" portType="sqp:StockQuotePT"
operation="getQuote" inputVariable="invocationrequest"
outputVariable="invocationresponse"/>
PortType in external stockquote.wsdl
<portType name="StockquotePT">
<operation name="getQuote">
<input message="tns:GetQuoteInput"/>
<output message="tns:GetQuoteOutput"/>
</operation>
</portType>
LoanApproval Sample
Import two external Web Services plus one external definition file in WSDL
<import namespace="http://tempuri.org/services/loandefinitions"
location="http://localhost:8080/bpws4j-samples/loanapproval/loandefinitions.wsdl"/>
LoanApprover Web Service:
<import namespace="http://tempuri.org/services/loanapprover"
location="http://localhost:8080/bpws4j-samples/loanapproval/loanapprover.wsdl"/>
LoanAssessor Web Service:
<import namespace="http://tempuri.org/services/loanassessor"
location="http://localhost:8080/bpws4j-samples/loanapproval/loanassessor.wsdl"/>
<PartnerLinkType> in WSDL
<plnk:partnerLinkType xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-link/"
name="loanApprovalLinkType">
<plnk:role name="approver">
<plnk:portType name="apns:loanApprovalPT"/>
</plnk:role>
</plnk:partnerLinkType>
<portType name="loanApprovalPT"> portType in loanapprover.wsdl
<operation name="approve">
<input message="loandef:creditInformationMessage"/>
<output message="tns:approvalMessage"/>
<fault name="loanProcessFault"
message="loandef:loanRequestErrorMessage"/>
</operation>
</portType>
<PartnerLinkType> in WSDL
<plnk:partnerLinkType xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-link/" na
<plnk:role name="assessor">
<plnk:portType name="asns:riskAssessmentPT"/>
</plnk:role>
</plnk:partnerLinkType>
<portType name="riskAssessmentPT"> portType in loanassessor.wsdl
<operation name="check">
<input message="loandef:creditInformationMessage"/>
<output message="tns:riskAssessmentMessage"/>
<fault name="loanProcessFault"
message="loandef:loanRequestErrorMessage"/>
</operation>
</portType>
Links defined for dependencies between the
activities in BEPL
<links>
<link name="receive-to-assess"/>
<link name="receive-to-approval"/>
<link name="approval-to-reply"/>
<link name="assess-to-setMessage"/>
<link name="setMessage-to-reply"/>
<link name="assess-to-approval"/>
</links>
<receive name="receive1" partnerLink="customer" Receive in BEPL
portType="apns:loanApprovalPT"
operation="approve" variable="request"
createInstance="yes"> condition
<source linkName="receive-to-assess"
transitionCondition="bpws:getVariableData('request', 'amount')<10000"/>
<source linkName="receive-to-approval"
transitionCondition="bpws:getVariableData('request', 'amount')>=10000"/>
</receive>
<link name="receive-to-assess"/>
<link name="receive-to-approval"/>
<portType name="loanApprovalPT">
<operation name="approve"> portType in loanapprover.wsdl
<input message="loandef:creditInformationMessage"/>
<output message="tns:approvalMessage"/>
<fault name="loanProcessFault"
message="loandef:loanRequestErrorMessage"/>
</operation>
</portType>
<Invoke> in BEPL
<invoke name="invokeAssessor" partnerLink="assessor"
portType="asns:riskAssessmentPT"
operation="check" <link name="receive-to-assess"/>
inputVariable="request" <link name="assess-to-setMessage"/>
outputVariable="riskAssessment"> <link name="assess-to-approval"/>
<target linkName="receive-to-assess"/>
<source linkName="assess-to-setMessage"
transitionCondition="bpws:getVariableData('riskAssessment', 'risk')='low'"/>
<source linkName="assess-to-approval"
transitionCondition="bpws:getVariableData('riskAssessment', 'risk')!='low'"/>
</invoke>
<portType name="riskAssessmentPT">
<operation name="check"> condition
<input message="loandef:creditInformationMessage"/>
<output message="tns:riskAssessmentMessage"/>
<fault name="loanProcessFault"
message="loandef:loanRequestErrorMessage"/>
</operation> portType in loanassessor.wsdl
</portType>
A Sample – LoanApproval.bepl
• <process name="loanApprovalProcess"
• targetNamespace="http://acme.com/loanprocessing"
• suppressJoinFailure="yes"
• xmlns="http://schemas.xmlsoap.org/ws/2003/03/business-process/"
• xmlns:lns="http://loans.org/wsdl/loan-approval"
• xmlns:loandef="http://tempuri.org/services/loandefinitions"
• xmlns:asns="http://tempuri.org/services/loanassessor"
• xmlns:apns="http://tempuri.org/services/loanapprover">
• <variables>
• <variable name="request"
• messageType="loandef:creditInformationMessage"/>
• <variable name="riskAssessment"
• messageType="asns:riskAssessmentMessage"/>
• <variable name="approvalInfo"
• messageType="apns:approvalMessage"/>
• <variable name="error"
• messageType="loandef:loanRequestErrorMessage"/>
• </variables>
• <partnerLinks>
• <partnerLink name="customer"
• partnerLinkType="lns:loanApprovalLinkType"
• myRole="approver"/>
• <partnerLink name="approver"
• partnerLinkType="lns:loanApprovalLinkType"
• partnerRole="approver"/>
• <partnerLink name="assessor"
• partnerLinkType="lns:riskAssessmentLinkType"
• partnerRole="assessor"/>
• </partnerLinks>
• <faultHandlers>
• <catch faultName="lns:loanProcessFault"
• faultVariable="error">
• <reply partnerLink="customer"
• portType="apns:loanApprovalPT"
• operation="approve"
• variable="error"
• faultName="invalidRequest"/>
• </catch>
• </faultHandlers>
• <flow>
• <links>
• <link name="receive-to-assess"/>
• <link name="receive-to-approval"/>
• <link name="approval-to-reply"/>
• <link name="assess-to-setMessage"/>
• <link name="setMessage-to-reply"/>
• <link name="assess-to-approval"/>
• </links>
• <receive name="receive1" partnerLink="customer"
• portType="apns:loanApprovalPT"
• operation="approve" variable="request"
• createInstance="yes">
• <source linkName="receive-to-assess"
• transitionCondition="bpws:getVariableData('request',
'amount')<10000"/>
• <source linkName="receive-to-approval"
• transitionCondition="bpws:getVariableData('request',
'amount')>=10000"/>
• </receive>
• <invoke name="invokeAssessor" partnerLink="assessor"
• portType="asns:riskAssessmentPT"
• operation="check"
• inputVariable="request"
• outputVariable="riskAssessment">
• <target linkName="receive-to-assess"/>
• <source linkName="assess-to-setMessage"
• transitionCondition="bpws:getVariableData('riskAssessment',
'risk')='low'"/>
• <source linkName="assess-to-approval"
• transitionCondition="bpws:getVariableData('riskAssessment',
'risk')!='low'"/>
• </invoke>
• <assign name="assign">
• <target linkName="assess-to-setMessage"/>
• <source linkName="setMessage-to-reply"/>
• <copy>
• <from expression="'yes'"/>
• <to variable="approvalInfo" part="accept"/>
• </copy>
• </assign>
• <invoke name="invokeapprover"
• partnerLink="approver" portType="apns:loanApprovalPT"
• operation="approve"
• inputVariable="request"
• outputVariable="approvalInfo">
• <target linkName="receive-to-approval"/>
• <target linkName="assess-to-approval"/>
• <source linkName="approval-to-reply" />
• </invoke>
• <reply name="reply" partnerLink="customer"
portType="apns:loanApprovalPT"
• operation="approve" variable="approvalInfo">
• <target linkName="setMessage-to-reply"/>
• <target linkName="approval-to-reply"/>
• </reply>
• </flow>
• </process>
Related docs
