Simple transformation to JSON error

[johnm16]

Hi Folks,

I created a very basic simple transformation to convert a flat ABAP structure with 5 fields into XML.

This is the structure:

USERNAME	1 Types	ZDE_USERNAME	STRING
PASSWORD	1 Types	ZDE_PASSWORD	STRING
CLIENT_ID	1 Types	ZDE_CLIENT_ID	STRING
CLIENT_SECRET	1 Types	ZDE_CLIENT_SECRET	STRING
GRANT_TYPE	1 Types	ZDE_GRANT_TYPE	STRING

And this is the transformation:

<?sap.transform simple?>
<tt:transform xmlns:tt="http://www.sap.com/transformation-templates" xmlns:ddic="http://www.sap.com/abapxml/types/dictionary" xmlns:def="http://www.sap.com/abapxml/types/defined">
  <tt:root name="ACCESS_TOKEN" type="ddic:ZSTY_ACCESS_TOKEN"/>
  <tt:template>
    <access_token>
      <username tt:value-ref=".ACCESS_TOKEN.USERNAME"/>
      <password tt:value-ref=".ACCESS_TOKEN.PASSWORD"/>
      <client_id tt:value-ref=".ACCESS_TOKEN.CLIENT_ID"/>
      <client_secret tt:value-ref=".ACCESS_TOKEN.CLIENT_SECRET"/>
      <grant_type tt:value-ref=".ACCESS_TOKEN.GRANT_TYPE"/>
    </access_token>
  </tt:template>
</tt:transform>

I call the transformation:

CALL TRANSFORMATION zca_access_token
             SOURCE access_token = ls_data
         RESULT XML lv_xstring.

And it works perfectly; I get exactly the XML output intended:

<?xml version="1.0" encoding="utf-8"?>
<access_token>
	<username>xxxxxxxxxxxxxxxxxxxxxxxx</username>
	<password>yyyyyyyyyyyyyyyyyyyyyyyy</password>
	<client_id>vvvvvvvvvvvvvvvvvvvvvvv</client_id>
	<client_secret>zzzzzzzzzzzzzzzzzzz</client_secret>
	<grant_type>password</grant_type>
</access_token>

So far so good.

Now I want to derive the JSON version of the XML, so I do this:

lr_writer = cl_sxml_string_writer=>create( type = if_sxml=>co_xt_json ).
CALL TRANSFORMATION zca_access_token
             SOURCE access_token = ls_data
         RESULT XML lr_writer.

But it throws an ABAP error:

Executing the 'OpenElement' operation leads to an invalid XML document

Why? (I expect the answer is obvious, but I've never worked with JSON transformations before).

Cheers

John Moulding.

[Andre_Fischer]

I am using the following library from the xco libraries in order to generate and read json strings.

JSON | SAP Help Portal

This is however only available as of SAP S/4HANA 2021 or in SAP BTP ABAP Environment.

Kind regards,

Andre

[johnm16]

Thank you Andre,

unfortunately (and I should have mentioned this), we're on ERP ECC6.

I think the issue lies with the transformation, which should be specific to JSON-XML, but I can't find any examples...

Cheers

John

[Andre_Fischer]

Maybe this blog post contains answers for you?

ABAP: Fast JSON Serialization | SAP Blogs

Though the author 8ae6723ab3fa43a8980099fe48f90b04 reported problems when using the xco libraries he in detail explains all the other options that should be available in your release.

[johnm16]

Hi Andre,

Timo's article is comprehensive and thorough, but it assumes a reasonable knowledge of transformations. Whereas I didn't even know that a JSON transformation had to be different from an XML transformation (I wasn't able to find any basic pointers on creating a simple transformation for JSON output, although I'm sure they're out there).

Anyway, I have an answer. I adapted my original XML transformation (above) to match the relevant lines in DEMO_ST_JSON_TABLE; this is the new JSON-specific version:

<?sap.transform simple?>
<tt:transform xmlns:tt="http://www.sap.com/transformation-templates" xmlns:ddic="http://www.sap.com/abapxml/types/dictionary">
  <tt:root name="ACCESS_TOKEN" type="ddic:ZSTY_EDOC_ACCESS_TOKEN_IN"/>
  <tt:template>
    <object>
      <str name="username">
        <tt:value ref="access_token.username"/>
      </str>
      <str name="password">
        <tt:value ref="access_token.password"/>
      </str>
      <str name="client_id">
        <tt:value ref="access_token.client_id"/>
      </str>
      <str name="client_secret">
        <tt:value ref="access_token.client_secret"/>
      </str>
      <str name="grant_type">
        <tt:value ref="access_token.grant_type"/>
      </str>
    </object>
  </tt:template>
</tt:transform>

And it works.

Thanks to everyone who read this, and I hope it helps another Newbie out there.

John