Calling Subtemplates (SAP Library - Application Development on AS ABAP)

Calling Subtemplates

A subtemplate tmpl can be called in any other template with the ST command tt:apply.

<tt:apply name="tmpl" [ref="node"]>
[<tt:with-root name="root1" [ref="node1"] />
   <tt:with-root name="root2" [ref="node2"] />
   ...]
[<tt:with-parameter name="para1" [ref="node1"|val="val1"|var="var1"] />
   <tt:with-parameter name="para2" [ref="node2"|val="val2"|var="var2"] />
   ...]
</tt:apply>

The subtemplate is processed at this point when the including template is executed.

● If separate data roots are declared using tt:root in the called subtemplate, you can set them with the ST command tt:with-root. You then cannot specify the optional attribute ref in the apply command.

● tt:with-root sets the data root of the name to the node specified in ref or binds the data root to the ABAP data object that is currently bound to the specified node. If ref is not specified, the current node of the calling template is used. Local data roots that are not bound to a node remain undefined – that is, they do not refer to an ABAP data object. At the beginning of a subtemplate of this type, the current node is undefined.

● If no separate data roots are declared using tt:root in a subtemplate tmpl, the root node of the tree structure of the called subtemplate is set either explicitly with the optional attribute ref or implicitly to the current node of the calling template at the call position.

● If formal parameters are declared using tt:parameter in the called subtemplate, you can use the ST command tt:with-parameter to link them to actual parameters. As actual parameters, you can use refto specify data roots, you can use varto specify variables, and you can use val to specify values. Depending on the kind of formal parameter, the values of the specified actual parameters are either passed in the call or copied when the subtemplate ends (see example below).

In this case, you can regard the parameter transfer as a special case of assignment, which means that the same principle applies as for tt:assign:

○ An assignment with data nodes as the target is possible only during deserialization.

○ An assignment with data nodes as the source is possible only during serialization.

Examples Without Parameter Passing

The following simple transformation contains two templates: a main template TEMP_MAIN and a subtemplate TEMP_SUB without its own data roots. The subtemplate is bound to the main template seven times with tt:apply; the respective current node is set with tt:ref beforehand. This ST program can transform a nested structure symmetrically .

<tt:transform template="TEMP_MAIN"
xmlns:tt="http://www.sap.com/transformation-templates">

<tt:root name="ROOT"/>

<tt:template name="TEMP_MAIN">

</week>
</tt:template>

  <tt:template name="TEMP_SUB">
    <name>
      <tt:value ref="$ref.name" />
    </name>
    <work>
      <tt:value ref="$ref.work" />
    </work>
  </tt:template>

</tt:transform>

The following ABAP program can call the transformation:

TYPES: BEGIN OF day,
         name TYPE string,
         work(1) TYPE c,
       END OF day.

DATA: BEGIN OF week,
        day1 TYPE day,
        day2 TYPE day,
        day3 TYPE day,
        day4 TYPE day,
        day5 TYPE day,
        day6 TYPE day,
        day7 TYPE day,
      END OF week.

DATA xml_string TYPE string.
DATA result LIKE week.

week-day1-name = 'Monday'.    week-day1-work = 'X'.
week-day2-name = 'Tuesday'.   week-day2-work = 'X'.
week-day3-name = 'Wednesday'. week-day3-work = 'X'.
week-day4-name = 'Thursday'.  week-day4-work = 'X'.
week-day5-name = 'Friday'.    week-day5-work = 'X'.
week-day6-name = 'Saturday'.  week-day6-work = ' '.
week-day7-name = 'Sunday'.    week-day7-work = ' '.

CALL TRANSFORMATION ...
SOURCE root = week
RESULT XML xml_string.

CALL TRANSFORMATION ...
SOURCE XML xml_string
RESULT root = result.

The result of the serialization is the following:

<week>
<day1>
    <name>Monday</name>
    <work>X</work>
</day1>
<day2>
    <name>Tuesday</name>
   <work>X</work>
</day2>
<day3>
  <name>Wednesday</name>
   <work>X</work>
</day3>
<day4>
    <name>Thursday</name>
    <work>X</work>
</day4>
<day5>
    <name>Friday</name>
   <work>X</work>
</day5>
<day6>
    <name>Saturday</name>
    <work/>
</day6>
<day7>
    <name>Sunday</name>
    <work/>
</day7>
</week>

After deserialization, result has the same contents as struc.

The simple transformation below has the same function as the previous one and can be called with the same result using the ABAP program specified there. In contrast to the transformation in the previous example, subtemplate TEMP_SUB has a separate data root here, local, to which another data node tt.apply is passed during each bind.

<tt:transform template="TEMP_MAIN"
xmlns:tt="http://www.sap.com/transformation-templates">

<tt:root name="ROOT"/>

<tt:template name="TEMP_MAIN">

</week>
</tt:template>

<tt:template name="TEMP_SUB">
    <tt:context>
      <tt:root name="local" />
    </tt:context>
    <name>
       <tt:value ref="local.name" />
    </name>
    <work>
       <tt:value ref="local.work" />
    </work>

</tt:template>

</tt:transform>

The simple transformation below also has the same function as the ones before. In this case, subtemplate TEMP_SUB has two separate data roots, local1and local2, to which data nodes are passed in command tt.apply.

<tt:transform template="TEMP_MAIN"
xmlns:tt="http://www.sap.com/transformation-templates">

<tt:root name="ROOT"/>

<tt:template name="TEMP_MAIN">

</week>
</tt:template>

<tt:template name="TEMP_SUB">
    <tt:context>
      <tt:root name="local1" />
      <tt:root name="local2" />
    </tt:context>
    <name>
      <tt:value ref=".local1" />
    </name>
    <work>
      <tt:value ref=".local2" />
    </work>
</tt:template>

</tt:transform>

The previous example demonstrates the use of local data roots and their addressing. In a real case, subtemplates help to reuse code and make simple transformations clearer.

Example with Parameter Passing

The transformation below shows how parameters are passed to a subtemplate:

<tt:transform xmlns:tt="http://www.sap.com/transformation-templates">

<tt:variable name="VARI1" val="1"/>
<tt:variable name="VARI2" val="2"/>
<tt:variable name="VARI3" val="3"/>

<tt:template>
    <tt:apply name="SUB">
      <tt:with-parameter name="PARA1" var="VARI1"/>
      <tt:with-parameter name="PARA2" var="VARI2"/>
      <tt:with-parameter name="PARA3" var="VARI3"/>
    </tt:apply>
    <X0>

</X0>
</tt:template>

<tt:template name="SUB">
    <tt:context>
      <tt:parameter kind="in" name="PARA1" val="4"/>
      <tt:parameter kind="out" name="PARA2"/>
      <tt:parameter kind="in/out" name="PARA3"/>
    </tt:context>
    <tt:assign to-var="PARA2" var="PARA3"/>
    <tt:assign to-var="PARA3" var="PARA1"/>
    <tt:assign to-var="PARA1" val="555"/>
</tt:template>

</tt:transform>

The result of the transformation is:

The input parameter PARA1 is changed in the subtemplate, but the changed value is not passed back to the actual parameter VARI1.

The output parameter PARA2 is set to the value of actual parameter VARI3, which is passed to the subtemplate, and this value is returned to the actual parameter VARI2.

The input/output parameter PARA3 is set to the value of actual parameter VARI1, which is passed to the subtemplate, and this value is returned to the actual parameter VARI3.