[CONF] Apache Ode: assign (page edited)

confluence Mon, 23 Apr 2007 08:23:23 -0700

Page Edited : ODExSITE : assign

assign has been edited by Maciej Szefler (Apr 23, 2007).

Content:

Name

<assign> — update the values of variables with new data

Synopsis

<assign validate="yes|no"? standard-attributes>
   standard-elements
   (
   <copy keepSrcElementName="yes|no"? ignoreMissingFromData="yes|no"?>
      from-spec
      to-spec
   </copy>
   |
   <extensionAssignOperation>
      assign-element-of-other-namespace
   </extensionAssignOperation>
   )+
</assign>


throws bpel:invalidVariables, bpel:selectionFailure, bpel:subLanguageExecutionFault, bpel:uninitializedVariable, bpel:mismatchedAssignmentFailure, bpel:uninitializedPartnerRole



Description
The <assign> activity can be used to copy data from one variable to another, as well as to construct and insert new data using expressions. The <assign> activity can also be used to copy endpoint references to and from partnerLinks. 

Each <assign> is made up of any number of <copy> entries which are each made up of a "to-spec" (lvalue), and a from-spec (rvalue). 


	ignoreMissingFromData - (optional) Should the bpel:selectionFailure standard fault be suppressed?
	
		yes - suppress standard faults
		no - (default) do not suppress standard faults
	
	




	validate - (optional) validate modified variables?
	
		yes - the <assign> activity validates all the variables being modified by the activity. If the validation fails the [bpel:invalidVariables#invalidVariables] fault is thrown.
		no - (default) do not validate the modified variables

ODE currently disregards the value of this attribute — validation is never performed.
	
	




	<copy> - defines a lvalue, rvalue pair.
	
		keepSrcElementName - (optional) should the element name of the destination (as selected by the to-spec) be replaced by the elementname of the source (as selected by the from-spec)?
		
			yes - element names are replaced
			no - (default) element names are not replaced
		
		
		<from> - specifies the rvalue (see here)
		<to> - specifies the lvalue (see here)
	
	




	<extensionAssignOperation> - a container for assignment extensions. If the element contained within the extensionAssignOperation elementis not recognized by ODE and is not subject to a mustUnderstand="yes"requirement from an extension declaration then the element will be ignored.

ODE does not currently implement extensionAssingOperation functionality, and all such elements are ignored.




From/To-Spec Variants

The <assign> activity copies a type-compatible value from the source ("from-spec") to the destination ("to-spec"), using the <copy> element. The from-spec must be one of the following variants:


<from variable="BPELVariableName" part="NCName"?>
   <query queryLanguage="anyURI"?>?
      queryContent
   </query>
</from>


<from partnerLink="NCName" endpointReference="myRole|partnerRole" />


<from variable="BPELVariableName" property="QName" />


<from expressionLanguage="anyURI"?>_expression_</from>


<from><literal>literal value</literal></from>


<from/>  <!-- DO NOT USE -->


<from variable="BPELVariableName" extension="QName" />   <!-- non-standard extension -->



The <from extension="QName" /> from-spec variant is not part of the WS-BPEL 2.0 specification. It is a non-standard ODE extension. 

The to-spec must be one of the following variants:

<to variable="BPELVariableName" part="NCName"?>
   <query queryLanguage="anyURI"?>?
      queryContent
   </query>
</to>


<to partnerLink="NCName" />


<to variable="BPELVariableName" property="QName" />


<to expressionLanguage="anyURI"?>_expression_</to>


<to/> <!-- DO NOT USE -->


<to variable="BPELVariableName" extension="QName" /> <!-- ODE SPECIFIC -->


The <to extension="QName" /> to-spec variant is not part of the WS-BPEL 2.0 specification. It is a non-standard ODE extension. 

A to-spec must return an lvalue. If a to-spec does not return an lvalue then a bpel:selectionFailure will be thrown. In the context of XPath, an lvalue is a node-list containing a single node from a variable or a partnerLink identified by the to-spec (e.g. the XPath _expression_  concat("foo""bar") is not an lvalue). 

XPaths used as lvalues must begin with an XPath VariableReference.

Assignment is an atomic operation; that is, either all {{<copy>}}s succeed, or no changes are made.

In ODE, each <copy> is atomic.

Variable Variant
Selects value stored in a BPEL variable.

<to|from variable="BPELVariableName" part="NCName"?>
   <query queryLanguage="anyURI"?>?
      queryContent
   </query>
</to|from>


	variable - (required) name of the variable.
	part - (optional) if the type of this variable is a WSDL messageType this attribute may be used to provide the name of a part within that variable. This attriubte must not be used When the variable is defined using XML Schema types (simple or complex) or element
	<query> element may be used to select a value from the source or target variable or message part. The computed value of the query must be one of the following:
	
		a single XML node, for example an attribute or an element
		text (i.e. a text node, CDATA section, string-valuedXPath-_expression_, etc...)
	
	



PartnerLink Variant
Allows manipulation of the endpoint references associated with partnerLinks. 

<from partnerLink="NCName" endpointReference="myRole|partnerRole" />


<to partnerLink="NCName"  />


	partnerLink - name of partnerLink
	role - the role or "side" of the partnerLink
	
		myRole -  the endpoint reference of the process
		{partnerRole}} - the partner's endpoint reference
	
	



For from-specs, the role attribute must be specified, while for the to-spec, the assignment is only possible to the partnerRole, hence there is no need to specify the role. Therefore, the to-spec can only refer to a <partnerLink> of which the declaration specifies the partnerRole attribute. The type of the value referenced by partnerLink-style from/to-specs is always a <sref:service-ref> element.

An attempt during process execution to read a partner link before its partnerRole EPR is initialized results in the bpel:uninitializedPartnerRole standard fault. Partner roles of partner links are read when they are referenced in an <invoke> or the <from> part of a <copy> in an <assign> activity.

Property Variant
Allows data manipulation using properties. The property value generated by the from-spec is generated in the same manner as the value returned by the bpel:getVariableProperty() function. 

<to|from variable="BPELVariableName" property="QName" />


	variable - name of the variable referenced
	property - name of the property to apply to the variable



_expression_ Variant
In the _expression_ Variant, an _expression_ language (typically XPath), is used to calculate a value. 

<to|from expressionLanguage="anyURI"?>_expression_</from>


	expressionLanguage - (optional) identifies the _expression_ language
	_expression_ - the _expression_;  syntax is determined by the _expression_ language.



The computed value of the _expression_ must be one of the following:

	a single XML node, for example an attribute or an element
	text (i.e. a text node, CDATA section, string-valuedXPath-_expression_, etc...)



Literal Variant
The Literal Variant allows a literal value to be given as the rvalue.


<from><literal>literal value</literal></from>


	literal value - value to be assigned



The type of the literal value may be optionally indicated inline with the value by using XML Schema's instance type mechanism (xsi:type). The literal content must be either a single element or text. An empty <literal/> element is equivalent to an empty text node.

Empty Variant
The empty variant exist for extensibility purposes; it is not supported by ODE. 

<from|to/>


Variable Extension Variant (non-standard extension)
The variable extension variants are non-standard extensions implemented by ODE to allow manipulation of protocol-specific properties from within a BPEL process.

<from variable="BPELVariableName" extension="QName" />


	variable - message variable to read
	extension - qualified name of the extension



The variable referenced by this variant must be message-typed. The following extensions are supported:


Extension Namespace
Name
Description


urn:ode.apache.org/axis2-il/headers/
in
When using the AXIS2 integration layer, this extension returns the headers that were received with the message but that did not map to any message parts in the portType. The return value will be a wrapper element(with the same name as the  extension) containing the SOAP header elements. 


urn:ode.apache.org/axis2-il/headers/
out
When using the AXIS2 integration layer, this extension holds the headers that should be sent with the mesage but are not mapped to any message parts in the portType. The rvalue should be a wrapper element (with the same name as the  extension) containing the SOAP header elements to be sent.




The use of this feature is not encouraged. Processes using this feature will not be compatible with WS-BPEL 2.0 conformant systems.

Faults


	bpel:invalidVariables - A modified variable does not conform to its schema and the validate flag was set to yes.

ODE does not perform schema type validation, hence this fault is never thrown.

	bpel:selectionFailure - The node(s) selected by a from/to-spec is (are) invalid. This includes cases when the to-spec returns a node that is not an lvalue, when multiple nodes are selected, or when no node is selected.


	bpel:subLanguageExecutionFault - Evaluating the _expression_ (in the _expression_ variant), or the query (in the variable variant) generated an error. For example, if a divide-by-zero is attempted.


	bpel:uninitializedVariable - The variable referenced in the from-spec has not been initialized.


	bpel:mismatchedAssignmentFailure - The nodes selected by the to-spec and from-spec are not compatible. This could occur if for example an attempt was made to assign a text node to an element variable, or an element variable was assigned to a message variable.



Examples
The following assigns a childless element bar in namespace http://example.com to an element-typed variable myFooBarElemVar:

<assign>
   <copy>
      <from>
         <literal xmlns:foo="http://example.com">
            <foo:bar />
         </literal>
      </from>
      <to variable="myFooBarElemVar" />
   </copy>
</assign>


The following assigns the string "FooBar" to a string-typed variable myStringVar:

<assign>
   <copy>
      <from>
         <literal>
            <![CDATA[FooBar]]>
         </literal>
      </from>
      <to variable="myStringVar" />
   </copy>
</assign>


The following assigns the string "" (i.e. the empty string) to a string-typed variable myStringVar:

<copy>
      <from>
         <literal />
      </from>
      <to variable="myStringVar" />
   </copy>
</assign>


The following illustrates copying one variable (c1) to another (c2) as well as copying a variable part (address part of variable c1) to a variable of compatible element type (c3):



<assign>

   <copy>

      <from variable="c1" />

      <to variable="c2" />

   </copy>

   <copy>

      <from>$c1.address</from>

      <to variable="c3" />

   </copy>

</assign>

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[CONF] Apache Ode: assign (page edited)

Name

Synopsis

Description

From/To-Spec Variants

Variable Variant

PartnerLink Variant

Property Variant

_expression_ Variant

Literal Variant

Empty Variant

Variable Extension Variant (non-standard extension)

Faults

Examples

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