ABAP 2 JSON and JSON 2 ABAP with ST

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Facts

• Simple Transformations (ST) serialize ABAP to XML and deserialize XML to ABAP.
• JSON-writers of the sXML-Library consume JSON-XML and digest it to JSON.
• The statement CALL TRANSFORMATION handles JSON-sources as JSON-XML implicitly.

Conclusion

The result of an ST that produces JSON-XML can be fed into a JSON writer to produce JSON. The same transformation can be used to deserialize JSON directly (a JSON-reader could be switched in between, but is not necessary).

Example ST producing or consuming JSON-XML

<?sap.transform simple?>

<tt:transform xmlns:tt="http://www.sap.com/transformation-templates">
  <tt:root name="CARRIERS"/>
  <tt:template>
    <array>
      <tt:loop ref=".CARRIERS">
        <object>
          <str name="Carrier-Id">
            <tt:value ref="$ref.carrid"/>
          </str>
          <str name="Carrier">
            <tt:value ref="$ref.carrname"/>
          </str>
          <str name="URL">
            <tt:value ref="$ref.url"/>
          </str>
        </object>
      </tt:loop>
    </array>
  </tt:template>
</tt:transform>

Example ABAP calling ST

CLASS demo DEFINITION.
  PUBLIC SECTION.
    CLASS-METHODS main.
  PRIVATE SECTION.
    CLASS-METHODS: display_as_text
                    IMPORTING json TYPE xstring,
                  display_as_html
                    IMPORTING json TYPE xstring.
ENDCLASS.

CLASS demo IMPLEMENTATION.
  METHOD main.

    "Get some data into an internal table
    TYPES: BEGIN OF carrier,
            carrid  TYPE scarr-carrid,
            carrname TYPE scarr-carrname,
            url      TYPE scarr-url,
          END OF carrier.
    DATA carriers TYPE TABLE OF carrier.
    SELECT carrid carrname url
          FROM scarr
          INTO CORRESPONDING FIELDS OF TABLE carriers.

    "Create JSON-writer and call simple transformation
    DATA json_writer TYPE REF TO cl_sxml_string_writer.
    DATA writer TYPE REF TO if_sxml_writer.
    json_writer = cl_sxml_string_writer=>create( type = if_sxml=>co_xt_json ).
    writer ?= json_writer.
    writer->set_option( option = if_sxml_writer=>co_opt_linebreaks ).
    writer->set_option( option = if_sxml_writer=>co_opt_indent ).
    CALL TRANSFORMATION demo_st_json_table SOURCE carriers = carriers
                                    RESULT XML json_writer.

    "Get JSON-String from writer
    DATA json TYPE xstring.
    json = json_writer->get_output( ).

    "Two ways of displaying the JSON string
    display_as_text( json ).
    display_as_html( json ).

    "Back to ABAP, verify that transformation is symmetric

    DATA result LIKE carriers.
    CALL TRANSFORMATION demo_st_json_table SOURCE XML json
                                    RESULT carriers = result.
    ASSERT result = carriers.

  ENDMETHOD.
  METHOD display_as_text.
    "Simple output of JSON in text edit control
    DATA text TYPE string.
    text = cl_abap_codepage=>convert_from( json ).
    cl_demo_text=>show_string( text ).
  ENDMETHOD.
  METHOD display_as_html.
    "Beautified output of JSON in HTML browser
    DATA html TYPE string.
    CALL TRANSFORMATION sjson2html SOURCE XML json
                                  RESULT XML html.
    cl_abap_browser=>show_html( html_string = html ).
  ENDMETHOD.
ENDCLASS.

START-OF-SELECTION.
  demo=>main( ).

Note

If you replace type = if_sxml=>co_xt_json with type = if_sxml=>co_xt_xml10 when creating the sXML-writer, it becomes an XML-writer and you will get JSON-XML instead of JSON from the writer.