[CONF] Apache Ode: Flexible Assigns (page edited)

Thu, 02 Oct 2008 12:32:30 -0700

Page Edited : ODExSITE : Flexible Assigns

Flexible Assigns has been edited by Karthick Sankarachary (Oct 02, 2008).

(View changes)

Content:

Auto Complete Copy Destination (L-Value)

A lot of times, users expect the <copy> operation in a WS-BPEL assign activity to behave such that the path specified by the destination ("to-spec") is automatically created, if it doesn't already exist. By default, if the to-spec used within a <copy> operation does not select exactly one XML information item during execution, then the standard fault bpel:selectionFailure is thrown (as mandated by the spec).

To override this default behavior, we introduce a insertMissingToData attribute in the <copy> operation, which if it is set to "yes", will instruct the runtime to complete the (XPath) L-value specified by the to-spec, if no items were selected. For the sake of simplicity, we will complete the to-spec if and only if:

  1. It's a path _expression_ whose steps are separated by "/", and
  2. Its steps have an axis, which is either "child" or "attribute", and
  3. Its steps have no following predicates, and
  4. Its steps test the name of a node, without the use of wildcards.

Formally, the grammar of the to-spec, for which auto-complete is enabled, may be defined in terms of these productions: 

PathExpr ::= ("/" RelativePathExpr?) | RelativePathExpr 
    RelativePathExpr ::= ForwardStep (("/" ) ForwardStep)* 
    ForwardStep ::= (ForwardAxis QName) | AbbrevForwardStep 
    AbbrevForwardStep ::= "@"? QName 
    ForwardAxis ::= ("child" "::") | ("attribute" "::")


The example below illustrates the use of the insertMissingToData attribute. Let's say that the variable "response" is uninitialized. In that case, the first <copy> operation will fail, whereas the second one will succeed. 





<copy> 
        <from>$request.requestMessageData/typeIndicators/types:indicatorTwo</from> 
        <to>$response/typeIndicators/types:indicatorTwo</to> 
    </copy> 

    <copy insertMissingToData="yes"> 
        <from>$request.requestMessageData/typeIndicators/types:indicatorTwo</from> 
        <to>$response/typeIndicators/child::types:indicatorTwo</to> 
     </copy>





Add support for the ignoreMissingFromData attribute in <copy>



The attached patch adds support for the following attributes in the BPEL assign activity's copy operation: 



    
	
  1. The optional @ignoreMissingFromData attribute, which if it has the value of "yes", and the from-spec returns zero XML information items, then no bpel:selectionFailure is thrown, and the to-spec is not evaluated.
    2. 





    
	
  1. An extension @ignoreUninitializedFromVariable attribute, which if it has the value of "yes", and the from-spec contains an uninitialized variable, then no bpel:uninitializedVariable is thrown, and the to-spec is not evaluated.
    2. 





The informal syntax of the above attributes is shown below:





<copy ignoreMissingFromData="yes|no"? ignoreUninitializedFromVariable="yes|no"?> 
      from-spec to-spec 
</copy>

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