Iteration activities

Chapter 17 Working with WS-BPEL 2.0

Iteration activities

Iteration activities are another type of loop activitiy.

repeatUntil activity

The repeatUntil activity is used to define that the child activity is to be repeated until the specified <condition> becomes true. The <condition> is tested after the child activity completes. The repeatUntil activity is used to execute the child activity at least once.

Syntax:

<repeatUntil standard-attributes>
   standard-elements
   activity
   <condition expressionLanguage="anyURI"?>bool-expr>/condition>
</repeatUntil>

forEach activity

The forEach activity iterates its child scope activity exactly N+1 times where N equals the <finalCounterValue> minus the <startCounterValue>. If parallel="yes" then this is a parallel <forEach> where the N+1 instances of the enclosed <scope> activity should occur in parallel. An implicit flow is dynamically created with N+1 copies of the <forEach>'s <scope> activity as children. A <completionCondition> may be used within the <forEach> to allow the <forEach> activity to complete without executing or finishing all the branches specified.

Syntax:

<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>

Mapping

You design a repeatUntil activity and a forEach activity using a process with a "Loop" implementation type and respectively a "RepeatUntill" or "Foreach" loop type.

The following specific WS-BPEL 2.0 extended attribute is available from the property sheet of the process object with a "Loop" implementation type and a "While", "Untill" or "Foreach" loop type. The other attributes in that tab are the same as the ones for BPEL4WS 1.1:

Name	Internal code	Description
Expression language	expressionLanguage	Specifies the expression language used in the condition. When this attribute is not specified for one of the iteration elements, the attribute inherits its value from the <process> element. The default value for this attribute is: "urn:oasis:names:tc:wsbpel:2.0:sublang:xpath1.0", which represents the usage of [XPath 1.0] within WS-BPEL 2.0.

In addition, the following extended attributes are available from the property sheet of the process object with a "Loop" implementation type and a "Foreach" loop type:

Name	Internal code	Description
Counter name	counterName	Defines the variable used by the <forEach> activity to store the counter of the loop. During each repetition, a variable of the xsd:unsignedInt attribute is implicitly declared in the <forEach> activity's child <scope>. The name of the implicit variable is specified in the CounterName attribute
Start counter value	startCounterValue	Allows you to compute the initial value of the counter variable used by the <forEach> activity. It is evaluated when the <forEach> activity starts
Final counter value	finalCounterValue	Allows you to compute the final value of the counter variable used by the <forEach> activity. It is evaluated when the forEach activity starts.
Parallel	parallel	If the value of the parallel attribute is no then the activity is a serial <forEach>. If the value of the parallel attribute is yes then the activity is a parallel <forEach>.
Successful branches only	SuccessfulBranchesOnly	The <branches> element of the <forEach> activity represents an unsigned-integer expression used to define a completion condition. If the value of the successfulBranchesOnly attribute is no, all the <scope>'s which have completed (successfully or unsuccessfully) must be counted. If the successfulBranchesOnly attribute is yes, only <scope>'s which have completed successfully must be counted