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ST - tt:root, Data Roots

Other versions: 7.31 | 7.40 | 7.54

Syntax


<tt:root name="..." [[line-]type="..." 
      
             [length="..."] 
 
                  [decimals="..."]] 

                    [...] />

Effect

To be able to access ABAP data, an ST program must contain at least one declaration of a data root outside a template. The data roots are the interfaces of the ST program to the ABAP data objects, which you specify in the statement CALL TRANSFORMATION as source or target fields. Data roots are defined using the statement tt:root. A name must be assigned to the data root with the name attribute. It can be typed with the [line-]type attribute.

The data roots declared on the tt:transform level form the context of the main template and can be addressed directly within it. The data roots are not recognized in subtemplates. However, they can be bound to the local data roots of subtemplates when these templates are called.


Note

An ST program without a data root describes a constant XML fragment that does not access ABAP data. In the CALL TRANSFORMATION statement, the syntax requires you to specify source or target fields. Data objects specified when ST programs are called without data roots are ignored during serialization and not changed during deserialization. The example for literal texts uses ST programs without data roots.

Data Root Name

Use the name attribute to declare a symbolic name, which can be bound to an ABAP data object. This binding is achieved by assigning these names as bni to data object ei during serialization or to fi during deserialization, in the CALL TRANSFORMATION statement.

The symbolic name is not case-sensitive and must be unique. The namespace also includes the data roots declared using tt:parameter and the variables declared using tt:variable. No data roots other than the ones specified here can be used in the CALL TRANSFORMATION statement.

Typing the Data Root

The data root can be typed with a data type using the attribute type or line-type of tt:root. Whereas type directly specifies the type, line-type means that it is an internal table of the named type.

For data roots without explicit typing, no checks are made until the transformation is executed. Explicit typing is used to check the ST program statically. Examples of invalid operations that can then be recognized by the compiler are:

  • Access to a nonexistent structure component
  • Loop through a non-tabular node
  • Handling a structured node as elementary

Elementary ABAP types, types from the Repository, and types of the same ST program that are defined with tt:type can be specified as the value of [line-]type. Type specifications are subject to the same restrictions as the tt:value statement.

Accessing a Data Root

Access to a data root is described under Addressing the Data Roots. Serializations and deserializations are subject to the general restriction that the content of a data root cannot be modified by serialization; only write access is possible to a data root during deserialization.


Example

Six data roots including typing are defined in the following transformation. The data root R1 has the elementary ABAP type d, R2 has the type "internal table with elementary row type i", R3 has the type DSTRUCT from ABAP Dictionary, R4 has the type ABCD_STRUCT from the type group ABCD, and R5 is a table across the type ABCSTRUCT defined in the global class CL_ABC. The type of R6 is defined as the name STRUCT in the transformation itself.

...
<tt:transform
  xmlns:tt="http://www.sap.com/transformation-templates"
  xmlns:ddic="http://www.sap.com/abapxml/types/dictionary"
  xmlns:tp="http://www.sap.com/abapxml/types/type-pool/ABCD"
  xmlns:cl="http://www.sap.com/abapxml/types/class-pool/CL_ABC"
  xmlns:def="http://www.sap.com/abapxml/types/defined" >
  <tt:type name="STRUCT">
    <tt:node name="C1" type="I"/>
    <tt:node name="C2" type="I"/>
  </tt:type>
  <tt:root name="R1" type="D"/>
  <tt:root name="R2" line-type="I"/>
  <tt:root name="R3" type="ddic:DSTRUCT"/>
  <tt:root name="R4" type="tp:ABCDSTRUCT"/>
  <tt:root name="R5" line-type="cl:ABCSTRUCT"/>
  <tt:root name="R6" type="def:STRUCT"/>
...