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Covers WS-BPEL 2.0, its process structure, standard faults, default attribute values, and all important BPEL activities.
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Each BPEL process consists of the following: (a) BPEL code, which defines the orchestration flow; (b) WSDL interface, which defines the interface (and the related XML Schemas) of the BPEL process for its clients; (c) WSDL interfaces of the consumed services (partner links). Partner links define the relations between BPEL process and the web services. Figure 1 shows the overall structure of a BPEL process.
<process name="NCName" targetNamespace="anyURI"queryLanguage="anyURI"?expressionLanguage="anyURI"?suppressJoinFailure="yes|no"?exitOnStandardFault="yes|no"?xmlns="http://docs.oasisopen.org/wsbpel/2.0/process/executable"><extensions/>?<import/>*<partnerLinks/>?<messageExchanges/>?<variables/><correlationSets/>?<faultHandlers/>?<eventHandlers/>?activity</process>| activity | Two different types of processes:
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<plnk:partnerLinkType>
Characterizes a relationship between two services. We define roles played by each of the services. We specify the used portType of each service within the context of the conversation. Each <role> specifies exactly one WSDL portType. <plnk:partnerLinkType> is defined in the service WSDL document, not in the BPEL.
<wsdl:definitions name="NCName" targetNamespace="anyURI" ...>...<plnk:partnerLinkType name="NCName"><plnk:role name="NCName" portType="QName" /><plnk:role name="NCName" portType="QName" />?</plnk:partnerLinkType>...</wsdl:definitions>Example:
<plnk:partnerLinkType name="OrderLT"><plnk:role name="OrderService" portType="ord:OrderPT" /><plnk:role name="OrderRequester" portType="ord:OrderCallbackPT" /></plnk:partnerLinkType><partnerLink>
Defines the relation of the BPEL process to partner web services. For request-reply semantics specify both roles, for one-way semantics specify one role only.
<partnerLinks>?<!-- At least one role must be specified. --><partnerLink name="NCName"partnerLinkType="QName"myRole="NCName"?partnerRole="NCName"?initializePartnerRole="yes|no"?>+</partnerLink></partnerLinks>Example:
<partnerLinks><partnerLink name="Ordering"partnerLinkType="tns:OrderLT"myRole="OrderRequester" partnerRole="OrderService" /></partnerLinks><sref:service-ref>
Endpoint references associated with partnerRole and myRole of <partnerLink>s are manifested as service reference containers (<sref:service-ref>).
<sref:service-ref reference-scheme="URI">content</sref:service-ref>Default is WS-Addressing endpoint reference:
<sref:service-ref><addr:EndpointReference><addr:Address>http://example.com/auction/Registration/</addr:Address><addr:ServiceName>as:RegistrationService</addr:ServiceName></addr:EndpointReference></sref:service-ref>Variable Declaration
<variables>
Declare variables within a process or a scope. Variables hold XML data. Variable can be one of the following types: WSDL message type, XML Schema type, or XML Schema element. Variable is visible in the scope in which it is defined and in all nested scopes.
Syntax:
<variables><variable name="BPELVariableName"messageType="QName"?type="QName"?element="QName"?>+from-spec?</variable></variables>Example:
<variables><variable name="OrderForm"messageType="ord:OrderFormMsg" /></variables>Manipulating Variables
<assign>
Update and copy data between variables, expressions, and partner link endpoint references.
<assign validate="yes|no"? standard-attributes>standard-elements<copy keepSrcElementName="yes|no"?ignoreMissingFromData="yes|no"?>from-specto-spec</copy></assign>| from-spec |
17 1 2 <from variable="BPELVariableName" part="NCName"?>3 <query queryLanguage="anyURI"?>?4 queryContent5 </query>6 </from>7 <from partnerLink="NCName"8 endpointReference="myRole|partnerRole" />9 <from variable="BPELVariableName"10 property="QName" />11 <from expressionLanguage="anyURI"?>12 expression13 </from>14 <from>15 <literal>literal value16 </from>17 <from/> |
| to-spec |
13 1 2 <to variable="BPELVariableName" part="NCName"?>3 <query queryLanguage="anyURI"?>?4 queryContent5 </query>6 </to>7 <to partnerLink="NCName" />8 <to variable="BPELVariableName"9 property="QName" />10 <to expressionLanguage="anyURI"?>11 expression12 </to>13 <to/> |
| messageType | $VariableName.part/ns:node1/ns:node2/... |
| Type | $VariableName/ns:node1/ns:node2/... |
| Element | $VariableName/ns:node1/ns:node2/... |
Example:
<assign><copy><from>$Order/Item/Amount * $ExchangeRate<to>$OrderFrgn/Item/Amount</copy></assign><validate>
Validates the values of variable against the associated XML or WSDL data definition. For invalid validation, bpel:invalidVariables fault is thrown.
<validate variables="BPELVariableNames" standard-attributes>standard-elements</validate>Example:
<validate variables="Order OrderFrgn"/><sequence>
Defines a set of activities that will be executed in sequential order.
<sequence standard-attributes>standard-elementsactivity+</sequence>Example:
<sequence name="OrderProcessing"><receive .../><assign>...</assign><invoke .../><reply .../></sequence><flow>
Specifies activities that should be performed concurrently.
<flow standard-attributes>standard-elements<links>?<link name="NCName" />+</links>activity+</flow>Example:
<flow name="CheckPrice"><invoke name="CheckSupl1" .../><invoke name="CheckSupl2" .../><invoke name="CheckSupl3" .../></flow>To define synchronization dependencies between activities within <flow>, we use <links>. This way we define the order of execution. Links have to be declared within the <flow>.
Links: <targets> and <sources>
Define source and destination links for synchronization of flow activities. <source> is used to annotate an activity being a source of one or more links. <target> is used to annotate an activity being a target of one or more links. A link's target activity can be performed only after the source activity has been finished.
<targets>?<joinCondition expressionLanguage="anyURI"?>?bool-expr</joinCondition><target linkName="NCName" />+</targets><sources>?<source linkName="NCName">+<transitionCondition expressionLanguage="anyURI"?>?bool-expr</transitionCondition></source></sources>Example:
<flow><links><link name="TravelStatusToTicketRequest" /><link name="TicketRequestToTicketConfirmation" /></links><assign><sources><source linkName="TravelStatusToTicketRequest" /></sources><copy>...</copy></assign><invoke partnerLink="TicketConf" portType="tc:TicketPT"operation="ConfirmTicket" inputVariable="TicketRequestVar"outputVariable="TicektConfVar" ><targets><target linkName="TravelStatusToTicketRequest" /></targets><sources><source linkName="TicketRequestToTicketConfirmation" /></sources></invoke>...</flow><joinCondition>
Defines explicit join condition for incoming (<target>) links. Default is OR (at least one incoming link to be true). Positive join condition (true) is required for starting the activity. If join condition evaluates to false, bpel:joinFailure fault is thrown (except if suppressJoinFailure="yes"). Example:
<targets><joinCondition>$TicketApproved and $DiscountGiven</joinCondition><target linkName="OrderTicket" /><target linkName="IssuePayment" /></targets><transitionCondition>
Defines the condition for outgoing (<source>) links to have positive status. Default is that they evaluate to true. Example:
<sources><source linkName="IssuePaymentAutomatic"><transitionCondition>$Ticket.Amount < 1000</transitionCondition></source><source linkName=" IssuePaymentWithApproval"><transitionCondition>$Ticket.Amount >= 1000</transitionCondition></source></sources>suppressJoinFailure
Indicates whether a bpel:joinFailure fault should be suppressed or not. When not specified, it inherits its value from its closest enclosing construct.
suppressJoinFailure="yes|no"?name
To give a name to the BPEL activity (not related with links).
name="NCName"?<invoke>
Invokes an operation on a partner link web service.
<invoke partnerLink="NCName"portType="QName"?operation="NCName"inputVariable="BPELVariableName"?outputVariable="BPELVariableName"?standard-attributes>standard-elements<correlations>?<correlation set="NCName" initiate="yes|join|no"?pattern="request|response|request-response"? />+</correlations><catch faultName="QName"?faultVariable="BPELVariableName"?faultMessageType="QName"?faultElement="QName"?>*activity</catch><catchAll>?activity</catchAll><compensationHandler>?activity</compensationHandler><toParts>?<toPart part="NCName" fromVariable="BPELVariableName" />+</toParts><fromParts>?<fromPart part="NCName" toVariable="BPELVariableName" />+</fromParts></invoke>Example:
<invoke partnerLink="Ordering"portType="ord:OrderPT"operation="ConfirmOrder"inputVariable="Order"outputVariable="OrderConf" /><receive>
Waits for an incoming message (operation invocation). Typical uses: first process activity (createInstance="yes"); to wait for callbacks.
<receive partnerLink="NCName"portType="QName"?operation="NCName"variable="BPELVariableName"?createInstance="yes|no"?messageExchange="NCName"?standard-attributes>standard-elements<correlations>?<correlation set="NCName" initiate="yes|join|no"? />+</correlations><fromParts>?<fromPart part="NCName" toVariable="BPELVariableName" />+</fromParts></receive>Example:
<receive partnerLink="Ordering"portType="ord:OrderCallbackPT"operation="confirmOrder"variable="OrderConfirmation"/><pick>
Waits for one of several possible messages (operation invocations) or for a time-out.
<pick> can be the first process activity (createInstance="yes", no <onAlarm> allowed).<pick createInstance="yes|no"? standard-attributes>standard-elements<onMessage partnerLink="NCName"portType="QName"?operation="NCName"variable="BPELVariableName"?messageExchange="NCName"?>+<correlations>?<correlation set="NCName" initiate="yes|join|no"? />+</correlations><fromParts>?<fromPart part="NCName" toVariable="BPELVariableName" />+</fromParts>activity</onMessage><onAlarm>*(<for expressionLanguage="anyURI"?>duration-expr</for>|<until expressionLanguage="anyURI"?>deadline-expr</until>)activity</onAlarm></pick>Example:
<pick><onMessage partnerLink="Ordering"portType="ord:OrderPT"operation="confirmOrder"variable="OrderConfirmation">...</onMessage><onMessage partnerLink="Ordering"portType="ord:OrderPT"operation="cancelOrder"variable="OrderCancelation">...</onMessage><onAlarm><for>'PT12H'</for><!-- Order completion timed out --></onAlarm></pick><reply>
Sends a response for a request-response operation (synchronous). The request is received using either <receive>, <onMessage>, or <onEvent>.
<reply partnerLink="NCName"portType="QName"?operation="NCName"variable="BPELVariableName"?faultName="QName"?messageExchange="NCName"?standard-attributes>standard-elements<correlations>?<correlation set="NCName" initiate="yes|join|no"? />+</correlations><toParts>?<toPart part="NCName" fromVariable="BPELVariableName" />+</toParts></reply>Example:
<reply partnerLink="Ordering"portType="ord:OrderPT"operation="placeOrder"variable="Order"/><wait>
Waits for a specified time period or until a certain deadline.
<wait standard-attributes>standard-elements(<for expressionLanguage="anyURI"?>duration-expr</for>|<until expressionLanguage="anyURI"?>deadline-expr</until>)</wait>Example:
<wait><until>'2010-03-18T20:00+01:00'</until></wait><exit>
Immediately ends the BPEL process instance.
<exit standard-attributes>standard-elements</exit>Example:
<exit/><empty>
This activity does not do anything. It is useful for synchronization of concurrent activities.
<empty standard-attributes>standard-elements</empty>Example:
<empty/>deadline-expr
Used in until expression of <onAlarm> and <wait>. XML Schema date or dateTime types are used to express deadlines (following ISO 8601).
<until>'2010-01-01'</until><until>'2010-03-18T21:00:00+01:00'</until><until>'18:05:30Z'</until>duration-expr
Used in for expression of <onAlarm> and <wait>, and <repeatEvery> expression of <onAlarm>. XML Schema duration type is used (following ISO 8601).
<for>'PT4H10M'</for><for>'P1M3DT4H10M'</for><for>'P1Y11M14DT4H10M30S'</for>| P | Time duration designator. Duration expressions always start with P. |
| Y | Follows the number of years. |
| M | Follows the number of months or minutes. |
| D | Follows the number of days. |
| H | Follows the number of hours. |
| S | Follows the number of seconds. |
| T | Date-Time separator |
<if>
To model decisions. <if> selects exactly one activity from the set of choices.
<if standard-attributes>standard-elements<condition expressionLanguage="anyURI"?>bool-expr</condition>activity<elseif>*<condition expressionLanguage="anyURI"?>bool-expr</condition>activity</elseif><else>?activity</else></if>Example:
<if><condition>$Order.Amount > 1000</condition>... <!-- Make approval --><elseif><condition>$Order.Amount >= 0</condition>... <!-- Process automatically --></elseif><else>... <!-- Throw fault --></else></if><while>
Define a loop that repeats as long as the specified <condition> is true.
<while standard-attributes>standard-elements<condition expressionLanguage="anyURI"?>bool-expr</condition>activity</while>Example:
<while><condition>$Order.Amount < 1000</condition><sequence>...</sequence></while><repeatUntil>
Defines a loop that repeats until the specified <condition> becomes true. The <condition> is tested after the loop activities complete. Loop will execute at least once.
<repeatUntil standard-attributes>standard-elementsactivity<condition expressionLanguage="anyURI"?>bool-expr</condition></repeatUntil>Example:
<repeatUntil><sequence>...</sequence><condition>$Order.Amount >= 1000</condition></repeatUntil><forEach>
Iterates its child scope activities in parallel (parallel="yes") or sequential manner, exactly <finalCounterValue>-<startCounterValue>+1 times. An optional <completionCondition> allows the <forEach> activity to complete without executing or finishing all the branches specified.
<forEach counterName="BPELVariableName" parallel="yes|no"standard-attributes>standard-elements<startCounterValue expressionLanguage="anyURI"?>unsigned-integer-expression</startCounterValue><finalCounterValue expressionLanguage="anyURI"?>unsigned-integer-expression</finalCounterValue><completionCondition>?<branches expressionLanguage="anyURI"?successfulBranchesOnly="yes|no"?>unsigned-integer-expression</branches></completionCondition><scope ...>...</scope></forEach>Example:
<forEach counterName="NoOfSuppliers" parallel="yes"><startCounterValue>1</startCounterValue><finalCounterValue>3</finalCounterValue><scope><invoke name="CheckPrice" .../></scope></forEach><scope>
Defines a nested process scope with its own associated <partnerLinks>, <messageExchanges>, <variables>, <correlationSets>, <faultHandlers>, <compensationHandler>, <terminationHandler>, and <eventHandlers>.
<scope isolated="yes|no"? exitOnStandardFault="yes|no"?standard-attributes>standard-elements<partnerLinks/>?<messageExchanges/>?<variables/>?<correlationSets/>?<faultHandlers/>?<compensationHandler/>?<terminationHandler/>?<eventHandlers/>?activity</scope>Example:
<scope name="CheckSupplier"><partnerLinks>...</partnerLinks><variables>...</variables><faultHandlers>...</faultHandlers><sequence>...</sequence></scope><throw>
Generates a fault from inside the business process. Fault is identified by a qualified name.
<throw faultName="QName"faultVariable="BPELVariableName"?standard-attributes>standard-elements</throw>Example:
<throw faultName="tns:InvalidOrder" /><rethrow>
Rethrows the fault that was originally caught by the enclosing fault handler. <rethrow> can only be used within a fault handler (<catch> or <catchAll>).
<rethrow standard-attributes>standard-elements</rethrow>Example:
<rethrow /><faultHandlers>
Define the activities that are performed in response to faults. Fault handler can be <catch> or <catchAll>. They can be defined at the <process> level, within <scope>s, or inline for <invoke>.
<faultHandlers>?<!-- There must be at least one faultHandler --><catch faultName="QName"?faultVariable="BPELVariableName"?( faultMessageType="QName" | faultElement="QName" )? >*activity</catch><catchAll>?activity</catchAll></faultHandlers>Default fault handler:
<faultHandlers><catchAll><sequence><compensate /><rethrow /></sequence></catchAll></faultHandlers><eventHandlers>
Allow a process or scope to react on inbound messages (operation invocations) or on alarms. Event handler must contain at least one <onEvent> or <onAlarm> element. It can be defined at the <process> level or within <scope>s.
<eventHandlers>?<!-- There must be at least one onEvent or onAlarm. --><onEvent partnerLink="NCName"portType="QName"?operation="NCName"( messageType="QName" | element="QName" )?variable="BPELVariableName"?messageExchange="NCName"?>*<correlations>?<correlation set="NCName" initiate="yes|join|no"? />+</correlations><fromParts>?<fromPart part="NCName" toVariable="BPELVariableName" />+</fromParts><scope ...>...</scope></onEvent><onAlarm>*<!-- There must be at least one expression. -->(<for expressionLanguage="anyURI"?>duration-expr</for>|<until expressionLanguage="anyURI"?>deadline-expr</until>)?<repeatEvery expressionLanguage="anyURI"?>duration-expr</repeatEvery>?<scope ...>...</scope></onAlarm></eventHandlers>Example:
<eventHandlers><onEvent partnerLink="Ordering"portType="ord:OrderPT"operation="CancelOrder"messageType="ord:CancelOrderMsg"variable="CancelationDetails"><scope>...</scope></onEvent><onAlarm><for>'PT12H'</for><scope>...</scope></onAlarm></eventHandlers><compensationHandler>
Defines activities that are processed for compensation. Can be defined within <scope> or inline for <invoke>.
<compensationHandler>activity</compensationHandler>Default compensation handler:
<compensationHandler><compensate /></compensationHandler><compensateScope>
Starts compensation on a specified inner scope that has already completed successfully. <compensateScope> can only be used within a fault handler, another compensation handler, or a termination handler.
<compensateScope target="NCName" standard-attributes>standard-elements</compensateScope>Example:
<compensateScope target="PlaceOrder" /><compensate>
Starts compensation on all inner scopes that have already completed successfully, in default order. <compensate> can only be used within a fault handler, another compensation handler, or a termination handler.
<compensate standard-attributes>standard-elements</compensate>Example:
<compensate /><terminationHandler>
Defines the activities that are performed when a BPEL process is force terminated. Can be defined within <scope>.
<terminationHandler>activity</terminationHandler>Default compensation handler:
<terminationHandler><compensate /></terminationHandler><messageExchanges>
Used to name message exchanges.
<messageExchanges>?<messageExchange name="NCName" />+</messageExchanges>Default compensation handler:
<messageExchanges><messageExchange name="OrderME" /></messageExchanges>messageExchange attribute
Used to associate inbound message activities with <reply> activities (for example <receive> with <reply>). Use only if the execution can result in multiple pairs of inbound message activities and <reply>s.
object bpel:doXslTransform(string1, node-set, (string2, object)*)string1 = style sheet namenode-set = source document for the transformationstring2 = XSLT parameter nameobject = XSLT parameter value-can be XPath expressionFunction returns the result of transformation. Example:
<assign><copy><from>bpel:doXslTransform("OrderXSLT.xsl", $Order)</from><to variable="OrderTransformed" /></copy></assign><vprop:property>
Creates a unique name definition and associates it with an XML Schema type. <vprop:property> is defined in the service WSDL document, not in the BPEL.
<vprop:property name="NCName" type="QName"? element="QName"? />Example:
<vprop:property name="OrderIDNumber" type="ord:OrdIDType" /><vprop:propertyAlias>
Maps a property to a field in a specific message part or variable value. <vprop:property> is defined in the service WSDL document, not in the BPEL.
<vprop:propertyAlias propertyName="QName"messageType="QName"? part="NCName"?type="QName"?element="QName"?><vprop:query queryLanguage="anyURI"?>?queryContent</vprop:query></vprop:propertyAlias>Example:
<vprop:propertyAlias propertyName="tns:OrderIDNumber"messageType="ord:OrderMsg" part="data"><vprop:query>ord:OrderID</vprop:query></vprop:propertyAlias>bpel:getVariableProperty()
Extracts property values from variables.
object bpel:getVariableProperty(string1, string2)string1 - source variable name.string2 - property to select from variableExample:
bpel:getVariableProperty('Order','ord:OrderIDNumber')<correlationSets>
Correlation set is a set of properties shared by all messages in the correlated group of operations within a process instance. Can be declared within a process or scope, or inline for <invoke>, <receive>, <reply>, <onMessage>, and <onEvent>.
<correlationSets>?<correlationSet name="NCName" properties="QName-list" />+</correlationSets>Example:
<correlationSets><correlationSet name="Order"properties="ord:OrderIDNumber ord:CustomerID" /><correlationSet name="Invoice"properties="ord:InvoiceNumber" /></correlationSets><correlation>
Correlation can be used on <invoke>, <receive>, <reply>, <onMessage>, and <onEvent>. <correlation> indicates which correlation sets occur in the messages being sent and received. The initiate attribute is used to indicate whether the correlation set is being initiated (yes-initiated, join-initiated if not yet initiated, no-not initiated).
<correlations><correlation set="NCName"initiate="yes|join|no"?pattern="request|response|request-response"? />+</correlations>Example:
<receive partnerLink="Ordering" portType="ord:OrderPT"operation="PurchaseRequest" variable="Order"><correlations><correlation set="Order" initiate="yes" /></correlations></receive>...<invoke partnerLink="Ordering" portType="ord:OrderPT"operation="PurchaseResponse" inputVariable="OrderResponse"><correlations><correlation set="Order" initiate="no" /><correlation set="Invoice" initiate="yes" /></correlations></invoke>