Clean Core Strategy for S/4HANA: The Complete Guide

" BAD: Direct intervention in SAP standard
ENHANCEMENT-POINT ep_vbap_check IN PROGRAM sapmv45a.
  " Custom logic directly in SAP standard program
  IF vbap-matnr = 'SPECIAL'.
    vbap-kwmeng = vbap-kwmeng * 2.
  ENDIF.
END-ENHANCEMENT-POINT.

" BAD: Using non-released tables/fields
SELECT SINGLE * FROM but000 WHERE partner = lv_partner.
" but000 is not released - can change at any time!

" BAD: User-Exits/BADIs with unclean access
METHOD if_ex_badi_name~execute.
  " Direct access to internal SAP structures
  DATA(lv_internal) = cl_sap_internal_class=>get_data( ).
ENDMETHOD.

+------------------------------------------------------+
|                   SAP Standard                        |
|              (SAP S/4HANA Core)                       |
|                                                       |
|  +---------------------------------------------+     |
|  |    Released APIs & Extension Points         |     |
|  |  (Guaranteed stable by SAP)                 |     |
|  +----------------------+----------------------+     |
+-------------------------|--------------------------+
                          |
                          | Only via released interfaces
                          |
       +------------------v--------------------+
       |     Clean Core Extensions             |
       |                                       |
       |  - Tier-3: In-Stack (ABAP Cloud)      |
       |  - Key User Extensibility             |
       |  - Side-by-Side (BTP)                 |
       |  - API Integration                    |
       +---------------------------------------+

" Developed on BTP ABAP Environment
CLASS zcl_btp_sales_extension DEFINITION PUBLIC.
  PUBLIC SECTION.
    INTERFACES if_oo_adt_classrun.
ENDCLASS.

CLASS zcl_btp_sales_extension IMPLEMENTATION.
  METHOD if_oo_adt_classrun~main.
    " Access to S/4HANA via OData/APIs
    DATA(lo_http) = cl_web_http_client_manager=>create_by_http_destination(
      i_destination = cl_http_destination_provider=>create_by_url(
        i_url = 'https://my-s4hana.com/sap/opu/odata4/sap/api_salesorder_v1' )
    ).

    DATA(lo_request) = lo_http->get_http_request( ).
    lo_request->set_header_field( i_name = 'Accept' i_value = 'application/json' ).

    DATA(lo_response) = lo_http->execute( if_web_http_client=>get ).
    DATA(lv_json) = lo_response->get_text( ).

    " Custom business logic
    " - No access to S/4HANA internals
    " - Completely isolated
  ENDMETHOD.
ENDCLASS.

SAP GUI -> Settings -> Custom Fields and Logic
1. Choose object (e.g., Sales Order)
2. "Create New Field"
3. Field name: ZZ_PRIORITY
4. Data type: String(10)
5. Add to UI
-> Done! Field is available in table, CDS Views, and UI

1. Choose trigger: "Before Save - Sales Order"
2. Condition: IF NetAmount > 10000
3. Action: SET ZZ_PRIORITY = 'HIGH'
-> No ABAP knowledge needed!

" GOOD: ABAP Cloud Extension in S/4HANA
" Only use released APIs
CLASS zcl_sales_validator DEFINITION PUBLIC.
  PUBLIC SECTION.
    INTERFACES if_badi_interface.
ENDCLASS.

CLASS zcl_sales_validator IMPLEMENTATION.
  METHOD if_badi_interface~validate.
    " Access ONLY via Released APIs
    SELECT SINGLE *
      FROM i_salesorder  " <- Released CDS View (released by SAP)
      WHERE salesorder = @iv_order_id
      INTO @DATA(ls_order).

    " Business logic
    IF ls_order-TotalNetAmount > 50000.
      " Message via Released API
      DATA(lo_msg) = cl_message_helper=>get_instance( ).  " <- Released
      lo_msg->add_message(
        id     = 'ZMSG'
        number = '001'
        v1     = 'Approval required'
      ).
    ENDIF.
  ENDMETHOD.
ENDCLASS.

" In Eclipse ADT:
" 1. Open API (e.g., CDS View, Class)
" 2. Show Properties -> "API State"
" 3. Look for "Released" or "C1" (Cloud-Ready)

" Example: I_SalesOrder
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Sales Order'
@Metadata.allowExtensions: true
@ObjectModel.usageType.serviceQuality: #A
@VDM.viewType: #BASIC

" -> If @VDM.viewType is present: Part of Virtual Data Model (VDM)
"    = Released for Consumption!

define view I_SalesOrder
  as select from vbak  " <- vbak is NOT released, but I_SalesOrder is!
{
  key vbeln as SalesOrder,
      erdat as CreationDate,
      netwr as TotalNetAmount,
      waerk as TransactionCurrency
}

Filter: "API Type" -> "ABAP Cloud"
        "Product" -> "SAP S/4HANA"

Examples:
- I_SalesOrder, I_Customer, I_Product (CDS Views)
- CL_BALI_LOG (Application Logging)
- CL_NUMBERRANGE_RUNTIME (Number Ranges)
- CL_WEB_HTTP_* (HTTP Client)

" Transaction: ATC (ABAP Test Cockpit)
" Or in Eclipse ADT:
" Project -> Properties -> ABAP Development -> Code Inspector

" Check Variant: S4HANA_READINESS_REMOTE
" -> Shows all uses of non-released APIs

" BEFORE: Non-released
SELECT SINGLE * FROM but000 WHERE partner = @lv_partner.

" AFTER: Released API
SELECT SINGLE * FROM i_businesspartner
  WHERE businesspartner = @lv_partner
  INTO @DATA(ls_bp).

" Central wrapper for critical access
CLASS zcl_bp_access DEFINITION PUBLIC CREATE PRIVATE.
  PUBLIC SECTION.
    CLASS-METHODS:
      get_instance RETURNING VALUE(ro_instance) TYPE REF TO zcl_bp_access,

      get_business_partner
        IMPORTING iv_partner        TYPE bu_partner
        RETURNING VALUE(rs_partner) TYPE i_businesspartner.

  PRIVATE SECTION.
    CLASS-DATA go_instance TYPE REF TO zcl_bp_access.
ENDCLASS.

CLASS zcl_bp_access IMPLEMENTATION.
  METHOD get_instance.
    IF go_instance IS NOT BOUND.
      CREATE OBJECT go_instance.
    ENDIF.
    ro_instance = go_instance.
  ENDMETHOD.

  METHOD get_business_partner.
    " Today: Released API
    SELECT SINGLE * FROM i_businesspartner
      WHERE businesspartner = @iv_partner
      INTO @rs_partner.

    " If API is not sufficient:
    " TODO: Ask SAP for API extension (via Influence Request)
  ENDMETHOD.
ENDCLASS.

" In custom code everywhere:
DATA(ls_bp) = zcl_bp_access=>get_instance( )->get_business_partner( lv_partner ).
" -> If SAP API changes: only adjust zcl_bp_access, not 100 places

" BEFORE: Dynpro program with direct DB access
REPORT zsales_order_maintain.

PARAMETERS: p_order TYPE vbeln.

START-OF-SELECTION.
  " Direct table access
  UPDATE vbak SET status = 'CLOSED' WHERE vbeln = p_order.
  COMMIT WORK.

" AFTER: RAP Business Object
" -> see /en/rap-basics/ for details
MODIFY ENTITIES OF i_salesordertp
  ENTITY SalesOrder
    UPDATE FIELDS ( OverallSDProcessStatus )
    WITH VALUE #( ( SalesOrder = lv_order
                    OverallSDProcessStatus = 'C' ) )
  FAILED DATA(failed)
  REPORTED DATA(reported).

COMMIT ENTITIES.

# Azure DevOps / Jenkins Pipeline
- task: ABAP_ATC_Check
  inputs:
    checkVariant: 'CUSTOM_CLOUD_READINESS'
    failOnErrors: true
    excludePackages: '$TMP'  # Exclude test developments

# ABAP Development Standards (Example)

## Mandatory Rules
1. Only Released APIs (Check: API Business Hub)
2. ABAP Cloud Syntax (no CALL TRANSACTION, etc.)
3. RAP for transactional apps (no Dynpro)
4. CDS Views instead of SELECT on DB tables
5. No Implicit Enhancement Framework

## Recommendations
- Wrapper classes for frequently used APIs
- Unit Tests with Test Doubles (see /en/test-doubles-mocking/)
- EML for BO access (see /en/eml-guide/)

Pull Request Checklist:
[ ] ATC check green (Clean Core Variant)?
[ ] Only Released APIs used?
[ ] Unit Tests present (Coverage >= 80%)?
[ ] CDS Views documented (Labels/Descriptions)?
[ ] No Implicit Enhancements?

" ABAP Cloud Language Version: Compiler enforces Clean Core!

CLASS zcl_order_processor DEFINITION PUBLIC.
  PUBLIC SECTION.
    INTERFACES if_oo_adt_classrun.
ENDCLASS.

CLASS zcl_order_processor IMPLEMENTATION.
  METHOD if_oo_adt_classrun~main.
    " Allowed: Released API
    SELECT * FROM i_salesorder
      INTO TABLE @DATA(lt_orders).

    " Compiler error: vbak is not released!
    " SELECT * FROM vbak INTO TABLE @DATA(lt_vbak).
    " -> "vbak is not released for ABAP Cloud"

    " Compiler error: CALL TRANSACTION not allowed
    " CALL TRANSACTION 'VA03'.
    " -> "CALL TRANSACTION is not allowed in ABAP Cloud"
  ENDMETHOD.
ENDCLASS.

Eclipse ADT:
1. Create/Open Package
2. Properties -> ABAP Language Version
3. Select: "ABAP for Cloud Development"
-> All objects in this package are Clean Core compliant!

" User-Exit built into SAP Standard
ENHANCEMENT-SECTION zenhancement_vbap IN sapmv45a.
  ENHANCEMENT 1 zorder_validation.
    " Access to global variables of SAP program
    IF vbap-matnr CO '0123456789'.
      MESSAGE 'Invalid material number' TYPE 'E'.
    ENDIF.
  ENDENHANCEMENT.
END-ENHANCEMENT-SECTION.

" Step 1: Use BAdI (if available)
CLASS zcl_order_badi DEFINITION PUBLIC.
  PUBLIC SECTION.
    INTERFACES if_ex_sd_sales_item_check.  " <- SAP BAdI
ENDCLASS.

CLASS zcl_order_badi IMPLEMENTATION.
  METHOD if_ex_sd_sales_item_check~validate_item.
    " Access only via interface parameters (no global access)
    IF is_item-material CO '0123456789'.
      " Released API for Messages
      DATA(lo_msg) = cl_bali_message_setter=>create(
        severity = if_bali_constants=>c_severity_error
        id       = 'ZMSG'
        number   = '001'
      ).
      APPEND lo_msg TO ct_messages.
    ENDIF.
  ENDMETHOD.
ENDCLASS.

" Step 2: If no BAdI -> Wrapper Event
" See RAP Business Events: /en/events-raise-handler/

" Step 3: Long-term -> RAP Validation
" In Behavior Definition:
validation validateMaterialNumber on save
  { field Material; }

" Behavior Implementation:
METHOD validateMaterialNumber.
  READ ENTITIES OF zi_salesorder IN LOCAL MODE
    ENTITY SalesOrderItem
      FIELDS ( Material )
      WITH CORRESPONDING #( keys )
    RESULT DATA(lt_items).

  LOOP AT lt_items INTO DATA(ls_item) WHERE Material CO '0123456789'.
    APPEND VALUE #(
      %tky = ls_item-%tky
      %element-Material = if_abap_behv=>mk-on
    ) TO failed-salesorderitem.

    APPEND VALUE #(
      %tky = ls_item-%tky
      %msg = new_message_with_text(
        severity = if_abap_behv_message=>severity-error
        text     = 'Invalid material number'
      )
    ) TO reported-salesorderitem.
  ENDLOOP.
ENDMETHOD.