Creating composite transactions with looping logic

A composite transaction with looping logic allows you to iterate through a collection of objects and executes other requests based on each object. It is an extension of the basic composite transaction. (Refer to Understanding basic composite transactions before continuing with this section.)

The XML construct for the looping logic in the composite XML transaction is very similar to the XSLT <xsl:for-each> syntax. To include looping logic in a composite XML, use this syntax:

<for-each select="object-set-expression" var="varName">
  <!-- One or more <TCRMService/> (or <DWLAdminService/>) or <choose/> -->
    …
    …
</for-each>

The <for-each> XML tag contains a mandatory select attribute and a var attribute. The select attribute points to an object-set-expression, which is the kind of expression that will be evaluated to a collection of objects at runtime. The var attribute is a reference name that you can give in order to associate it with each object in the collection when the collection is iterated through. When the reference name is used in the rest of the composite, the reference name must be prefixed with a $ character.

Between the <for-each> and </for-each> XML tags, you can include one or more <TCRMService> (or <DWLAdminService>) XML requests. When the object-set expression is evaluated to return a collection of objects, each of the requests will be executed as many times as there are objects in the collection. You can also include another <choose> XML between the <for-each> and </for-each> XML tags. This in effect allows you do further qualify the loop with "if-then-else" logic.

The following is a sample composite XML transaction with looping logic. There are two requests in this composite: getPerson and updatePartyAddress. The looping logic is as follows:

1. Do a getPerson transaction for party ID 3004000123.
2. For each of the TCRMPartyAddressBObj objects returned from the TCRMPersonBObj:
   • If the EndDate has not been set, update the StartDate.
   • Otherwise, just produce an error message.

   <DWLCompositeServiceRequest>
     <GlobalFields>
         …
         …
     </GlobalFields>
     <TCRMService>
       <RequestControl>
         <requestID>100181</requestID>
         <DWLControl>
             …
             …
           <!-- The correlator ID for the getPerson transaction in this
                composite is 111. -->
           <transactionCorrelatorId>111</transactionCorrelatorId>
         </DWLControl>
       </RequestControl>
       <TCRMInquiry>
         <InquiryType>getPerson</InquiryType>
         <InquiryParam>
           <tcrmParam name="PartyId">3004000123</tcrmParam>
           <tcrmParam name="InquiryLevel">3/tcrmParam>
               …
               …
         </InquiryParam>
       </TCRMInquiry>
     </TCRMService>
   
     <!-- The object-set expression in this <for-each> gets the collection
          of TCRMPartAddressBObj from the getPerson response. The anAddress variable
          is a reference to each TCRMPartAddressBObj in the collection, which will be
          used in the rest of the composite. -->
     <for-each select="id.111.response.TCRMPersonBObj.TCRMPartyAddressBObj"
               var="anAddress">
       <choose>
         <!-- The boolean expression in this <when> tests if the EndDate in a
              TCRMPartAddressBObj has not been set. Note the use of the $anAddress
              variable to refer to each TCRMPartAddressBObj in the collection. -->
         <when test="$anAddress.EndDate = null">
           <TCRMService>
             <RequestControl>
               <requestID>100190</requestID>
               <DWLControl>
                   …
                   …
                 <transactionCorrelatorId>555</transactionCorrelatorId>
               </DWLControl>
             </RequestControl>
             <TCRMTx>
               <TCRMTxType>updatePartyAddress</TCRMTxType>
               <TCRMTxObject>TCRMPartyAddressBObj</TCRMTxObject>
               <TCRMObject>
                 <TCRMPartyAddressBObj>
                   <!-- Substitute all the necessary fields from the getPerson
                        response and the new StartDate to update the party address.
                        Note the use of the $anAddress variable to refer to each 
                        TCRMPartAddressBObj in the collection. -->
                   <PartyAddressIdPK>
                     {$anAddress.PartyAddressIdPK}
                   </PartyAddressIdPK>
                   <PartyId>{$anAddress.PartyId}</PartyId>
                   <StartDate>2000-01-31</StartDate>
                       …
                       …
                 </TCRMPartyAddressBObj>
               </TCRMObject>
             </TCRMTx>
           </TCRMService>
         </when>
         <!-- If the EndDate has been set, just produce an error message. -->
         <otherwise>
           <message errorId="6000" lang="100">Address already expired</message>
         </otherwise>
       </choose>
     </for-each>
   </DWLCompositeServiceRequest>
   

For more information on object-set expressions, see Creating object-set expressions.

For more information on boolean expressions, see Creating boolean expressions.

For more information on substitution expressions, see Example: Substituting values from another Request or Response.

For more information on looking up error messages, see Providing error messages using the error handling service.