Convert JSON to ABAP Internal Table and ABAP Data to JSON Format

JSON is a more and more used when dealing with communication between SAP System and different Information System Landscape.

Here we will start with a fast definition for JSON and JSON Data.

Then we will explain 3 different ways/Alternatives to convert JSON Data to ABAP Internal Table and ABAP Data to JSON.

Table of Contents

JSON vs ABAP Data

What’s JSON ?

JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data. (source)

This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance.

Convert JSON to ABAP Internal Table and ABAP Data to JSON Format

The handling of JSON data in ABAP is based on the following principles:

A JSON-XML format maps JSON data to XML.
XML readers and XML writers in sXML Library support JSON-XML and can be used as parsers and renderers of JSON data.
Direct transformations can be made between ABAP and JSON. Here, a canonical JSON representation of ABAP data called asJSON can be used for the identity transformation ID.

To learn more aout Json, Check one of the following JSON Books:

Handling & Convert JSON in ABAP

The handling/convert JSON data in ABAP is based on the following principles:( source )

A JSON-XML format maps JSON data to XML.
XML readers and XML writers in sXML Library support JSON-XML and can be used as parsers and renderers of JSON data.
Direct transformations can be made between ABAP and JSON. Here, a canonical JSON representation of ABAP data called as JSON can be used for the identity transformation ID.

IF_SXML=>CO_XT_JSON Interface

JSON-XML is a special XML format that enables JSON data to be described using an XML representation. A new format, IF_SXML=>CO_XT_JSON, has been added to the sXML Library, which enables to handle JSON using JSON-XML

The canonical JSON representation asJSON defines a mapping between ABAP types and JSON.
This is used in serializations and deserializations using the identity transformation ID.

JSON data can be specified in various forms as an XML source in the statement CALL TRANSFORMATION and a JSON writer can be specified as target.
The identity transformation ID supports JSON by using asJSON.

Sample Implementation of sXML ABAP to JSON

Here an excellent sample for the implementation of IF_SXML=>CO_XT_JSON interface ( source )

First, you should create the ABAP to JSON Writer with the CL_SXML_STRING_WRITER with Json as Type.
Then Call the transformation to convert the String to JSON formatted String .

The last Step is to retrieve the Outpout of the Writer in JSON.

DATA text TYPE string VALUE `Hello JSON, Im ABAP!`.
DATA writer TYPE REF TO cl_sxml_string_writer.
DATA json TYPE xstring.


"ABAP to JSON
writer = cl_sxml_string_writer=>create( type = if_sxml=>co_xt_json ).
CALL TRANSFORMATION id SOURCE text = text
                        RESULT XML writer.
json = writer->get_output( ).


"JSON to ABAP
text = `{"TEXT":"Hello ABAP, I'm JSON!"}`.
CALL TRANSFORMATION id SOURCE XML text
                        RESULT text = text.

Convert JSON <> ABAP with /UI2/CL_JSON Class

The /UI2/CL_JSON Class is delivered with UI2 Add-on. A sample Implementatioh /UI2/CL_JSON is (source)

This sample will include:

serialize table lt_flight into JSON, skipping initial fields and converting ABAP field names into camelCase
deserialize JSON string json into internal table lt_flight doing camelCase to ABAP like field name mapping
serialize ABAP object into JSON string

DATA: lt_flight TYPE STANDARD TABLE OF sflight,
      lrf_descr TYPE REF TO cl_abap_typedescr,
      lv_json   TYPE string.
 
  
SELECT * FROM sflight INTO TABLE lt_flight.
  
* serialize table lt_flight into JSON, skipping initial fields and converting ABAP field names into camelCase
lv_json = /ui2/cl_json=>serialize( data = lt_flight compress = abap_true pretty_name = /ui2/cl_json=>pretty_mode-camel_case ).
WRITE / lv_json.
 
CLEAR lt_flight.
  
* deserialize JSON string json into internal table lt_flight doing camelCase to ABAP like field name mapping
/ui2/cl_json=>deserialize( EXPORTING json = lv_json pretty_name = /ui2/cl_json=>pretty_mode-camel_case CHANGING data = lt_flight ).
 
* serialize ABAP object into JSON string
lrf_descr = cl_abap_typedescr=>describe_by_data( lt_flight ).
lv_json = /ui2/cl_json=>serialize( lrf_descr ).
WRITE / lv_json.

The most useful method for this API Json Class in ABAP are:

SERIALIZE: Serialize ABAP object into JSON
DESERIALIZE: Deserialize ABAP object from JSON string
GENERATE:Generates ABAP object from JSON
PRETTY_NAME: enumeration of modes, defined as constant /UI2/CL_JSON=>pretty_name.
ASSOC_ARRAYS:This option controls the way how hashed or sorted tables with unique keys serialized/deserialized

CL_TREX_JSON_SERIALIZER

An alternative to convert ABAP to JSON / SAP Internal Table to JSON is using the standard SAP class CL_TREX_JSON_SERIALIZER.

The CL_TREX_JSON SERIALIZER Class contains the following Methods:

CLASS_CONSTRUCTOR
CONSTRUCTOR
SERIALIZE
GET_DATA
RECURSE

You can read more this CL_TREX_JSON_SERIALIZER Class in this articleABAP to JSON / SAP Internal Table to JSON

ABAP JSON Parser And Mapper Sample Classes

In this section, you will find 2 opensources ABAP Class to handle all the actions when handling ABAP & JSON.

JSON Parser Class

A clean, reliable and compliant JSON parser and mapper to ABAP data the kind your mother would have encouraged you to hang out with.

Related SNOTES for Convert JSON & ABAP

2292558– Corrections for JSON serializer /UI2/CL_JSON
2300508– /UI2/CL_JSON deserialization of recursive structures
2330592– /UI2/CL_JSON corrections
2368774– /UI2/CL_JSON corrections – optimization for serialization of name/value tables
2382783– /UI2/CL_JSON corrections – bug fixes, supporting of firing of an exception on parsing error, helper methods for working with XSTRING output
2429758– /UI2/CL_JSON corrections – bug fixes control on serialization of NUMC types, support of on the fly ABAP data generation for unknown JSON structure
2480119– /UI2/CL_JSON corrections – fix for GENERATE method, fix for deserializing empty tables, auto-generation of initial fields with REF TO DATA, guided generation for initialized REF TO DATA fields (type of the referenced data is used)

More Resources ABAP & JSON Parser

I compiled here the most relevant links dealing with ABPA JSON Conversion and Parsing: