XML Processing in ABAP – Part 6

Introduction

This weblog series is about XML processing in ABAP, especially Simple Transformations. In Part one I claimed  that we can’t use Simple Transformations to transform nested hierarchical data into a relational data  model. In fact I was wrong at least from a theoretical point of view. Here I want to present a kind of solution. In fact this is only a proof-of-concept. I don’t recommend it as a best practice.

Advanced Simple Transformations

Let’s get into detail. We have a list of  elements and each has a text content and a nested list of  elements that have only text content. We want to write the text content of the  elements into a data root and the content of the its  child elements into another. Then we want to calculate a foreign key that links the  elements to their parents. Let me present a small ABAP Programm that defines the data structures and calls the transformation:

   DATA : BEGIN OF one,             nr    TYPE i,             value TYPE string,           END OF one.      DATA : begin of two,              nr    TYPE i,              nr2    TYPE i,              value TYPE string,            END OF two.      DATA l_tab_root1 like TABLE OF one.    DATA l_tab_root2 like TABLE OF two.   * XML string to deserialize    DATA l_var_input TYPE string.      DEFINE xml.      concatenate l_var_input &1 cl_abap_char_utilities=>cr_lf                  into l_var_input.    END-OF-DEFINITION.      xml ``.    xml `  <x1>L</x1>`.    xml `  <x1>M`.    xml `    <x2>h</x2>`.    xml `    <x2>w</x2>`.    xml `  </x1>`.    xml `  <x1>G`.    xml `    <x2>y</x2>`.    xml `    <x2>x</x2>`.    xml `    <x2>z</x2>`.    xml `  </x1>`.    xml ``.      CALL TRANSFORMATION z01_st_main         SOURCE XML l_var_input         RESULT root1 = l_tab_root1                root2 = l_tab_root2.

In fact all we need to solve this task is written down in my following weblogs: Part two and three. Here is the ST program:

<span> <?sap.transform simple?> <tt:transform xmlns:tt="</span><a class="jive-link-external-small" href="https://www.sap.com/transformation-templates">https://www.sap.com/transformation-templates</a><span>">   <tt:root name="ROOT1"/>   <tt:root name="ROOT2"/>     <tt:variable name="dummy"/>   <tt:variable name="counter1" val="I(0)"/>   <tt:variable name="counter2" val="I(0)"/>     <tt:template>            <tt:group>         <tt:cond frq="*">           <x1>             <tt:read type="C" var="dummy"/>             <tt:apply name="increment">               <tt:with-parameter name="value" var="counter1"/>             </tt:apply>             <tt:assign to-ref="ROOT1">               <tt:assign to-ref="NR" var="counter1"/>               <tt:assign to-ref="VALUE" var="dummy"/>             </tt:assign>             <!-- Initialize counter for inner loop -->             <tt:assign to-var="counter2" val="I(0)"/>             <!-- Work on inner loop -->             <tt:group>               <tt:cond frq="*">                 <x2>                   <tt:read type="C" var="dummy"/>                   <tt:apply name="increment">                     <tt:with-parameter name="value" var="counter2"/>                   </tt:apply>                   <tt:assign to-ref="ROOT2">                     <tt:assign to-ref="NR" var="counter1"/>                     <tt:assign to-ref="NR2" var="counter2"/>                     <tt:assign to-ref="VALUE" var="dummy"/>                   </tt:assign>                 </x2>               </tt:cond>             </tt:group>           </x1>         </tt:cond>       </tt:group>        </tt:template>     <tt:template name="increment">     <tt:context>       <tt:parameter kind="in/out" name="value"/>     </tt:context>       <tt:switch-var>       <tt:cond-var check="value=10">         <tt:assign to-var="value" val="I(11)"/>       </tt:cond-var>       <tt:cond-var check="value=9">         <tt:assign to-var="value" val="I(10)"/>       </tt:cond-var>       <tt:cond-var check="value=8">         <tt:assign to-var="value" val="I(9)"/>       </tt:cond-var>       <tt:cond-var check="value=7">         <tt:assign to-var="value" val="I(8)"/>       </tt:cond-var>       <tt:cond-var check="value=6">         <tt:assign to-var="value" val="I(7)"/>       </tt:cond-var>       <tt:cond-var check="value=5">         <tt:assign to-var="value" val="I(6)"/>       </tt:cond-var>       <tt:cond-var check="value=4">         <tt:assign to-var="value" val="I(5)"/>       </tt:cond-var>       <tt:cond-var check="value=3">         <tt:assign to-var="value" val="I(4)"/>       </tt:cond-var>       <tt:cond-var check="value=2">         <tt:assign to-var="value" val="I(3)"/>       </tt:cond-var>       <tt:cond-var check="value=1">         <tt:assign to-var="value" val="I(2)"/>       </tt:cond-var>       <tt:cond-var check="value=0">         <tt:assign to-var="value" val="I(1)"/>       </tt:cond-var>     </tt:switch-var>     </tt:template>  </tt:transform> </span>

Let me explain how it works. We define a sub template that increments a variable by  doing a case distinction. Because tt:loop can’t append to internal tables we use tt:assign and work a multiple XML elements using tt:group. We store the text content into variables using tt:read and store the numbers in variables counter1 and counter2, too.

After calling the program we get the expected result in l_tab_root1:

This is the content of l_tab_root2:

Discussion

• This solution isn’t symmetric and works for deserialization and not for serialization.
• It only works for a constant number of occurrences of elements in the input stream.
• I don’t assume it will be fast if we adapt it for huge datasets.

We can learn that an increment operator is very powerful and offers a new range of applications. True numerical  operations instead of the humble solution above could be a benefit to Simple Transformations although we have to be careful: In my opinion the best ST programs are the symmetric ones.