BPEL: looping over arrays (collections) by hand

Over the last days I have seen some questions on hand-looping over arrays.
A (long) while ago, Marc, a colleaque from Europe sent me a nice example. So I thought to publish it here. I hope I comply with copyrights here :-0

Imagine you get a collection of emps back from a service, as defined by the following schema (from DB adapter in this case)

 
   <xs:element name="EmpCollection" 
                type="EmpCollection"/>
   <xs:element name="Emp" type="Emp"/>
   <xs:complexType name="EmpCollection">
      <xs:sequence>
         <xs:element name="Emp" type="Emp" 
                     minOccurs="0" 
                     maxOccurs="unbounded"/>
      </xs:sequence>
   </xs:complexType>
   <xs:complexType name="Emp">
      <xs:sequence>
         <xs:element name="comm" type="xs:decimal"/>
         <xs:element name="deptno" type="xs:decimal"/>
         <xs:element name="empno" type="xs:decimal"/>
         <xs:element name="ename" type="xs:string"/>
         <xs:element name="hiredate" type="xs:dateTime"/>
         <xs:element name="job" type="xs:string"/>
         <xs:element name="mgr" type="xs:decimal"/>
         <xs:element name="sal" type="xs:decimal"/>
      </xs:sequence>
   </xs:complexType>

and accordingly a message type

    <message name="EmpCollection_msg">
        <part name="EmpCollection" 
              element="top:EmpCollection"/>
    </message>

The first step is to create a variable, based on the msg type that contains this collection, and 2 counters, one (i) for the running index, and one (n) for the length of the collection. All as shown below ..

    <variable name="EmpQuerySelect_p_deptno_OutputVariable" 
              messageType="ns1:EmpCollection_msg"/>
    <variable name="i" type="ns3:integer"/>
    <variable name="n" type="ns3:integer"/>

Step 2, consists of getting the count of nodes and assigning 1 to the counter

    <assign name="prepare_loop">
      <copy>
        <from expression="number(1)"/>
        <to variable="i"/>
      </copy>
      <copy>
        <from expression="ora:countNodes(
              'EmpQuerySelect_p_deptno_OutputVariable',
              'EmpCollection','/ns2:EmpCollection/Emp')"
        />
        <to variable="n"/>
      </copy>
    </assign>

Step 3, is the while loop and to get the information from a selected node, by applying the concepts further

    <while name="While_1" 
              condition="bpws:getVariableData('i') <= 
                         bpws:getVariableData('n')">
      <scope name="Scope_1">
        <variables>
          <variable name="selector" type="ns3:string"/>
          <variable name="element" element="ns2:Emp"/>
        </variables>
        <sequence name="Sequence_1">
          <assign name="Get_Element">
            <copy>
              <from expression="concat(
                   "/ns2:EmpCollection/Emp[",
                   string(bpws:getVariableData('i')),
                   "]")"/>
              <to variable="selector"/>
            </copy>
            <copy>
              <from expression="bpws:getVariableData 
                 ('EmpQuerySelect_p_deptno_OutputVariable',
                  'EmpCollection',
                  bpws:getVariableData('selector'))"
              />
              <to variable="element" query="/ns2:Emp"/>
            </copy>
          </assign>
          <empty name="Do_stuff_with_element_Var"/>
          <assign name="Increment_index">
            <copy>
              <from expression="bpws:getVariableData('i')+1"/>
              <to variable="i"/>
            </copy>
          </assign>
        </sequence>
      </scope>
    </while>

and voila - a loop over your collection is done :-)

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