ABAP Code Exits in CDS views

Introduction

In a CDS view it is possible to implement a Code Exit for an ABAP method call by defining a Virtual Element.

Please note that the call to the ABAP method will only be executed when the CDS view is consumed by something that handles annotations i.e. exposed as an Odata service, but not in transaction SE16N or the preview in Eclipse.

CDS view

First we create a standard CDS view, and add the virtual element we wish to connect to the ABAP method:

cast( '' as abap.char(255)) as text

ABAP class

The ABAP class must use the interface “if_sadl_exit_calc_element_read”, and implement the two methods “calculate” and “get_calculation_info”.

PUBLIC SECTION.
 INTERFACES if_sadl_exit_calc_element_read.

In the method “calculate” we can implement code to enrich the data from the CDS view. In the method “get_calculation_info” we can implement code to ensure that the data necessary for the use in method “calculate” are provided. If nothing is implemented in “get_calculation_info” all fields will be loaded with data prior to the call to the method “calculate”.

Note that it is not possible to add or delete rows in the dataset. SAP will do a check after the code exit to compare the number of rows, and any difference will result in an exception being raised – and a dump.

LOOP AT lt_calculated_data ASSIGNING FIELD-SYMBOL(<fs_data>).
  <fs_data>-text = 'Awesomeness'.
ENDLOOP.

Summary/use cases

When the ABAP method is called the complete dataset from the CDS view are passed. So access to all rows are possible. This could be used for calculations, or for more complex calls to methods or function modules like retrieving long texts from SO10.

References

SAP help: https://help.sap.com/viewer/cc0c305d2fab47bd808adcad3ca7ee9d/7.51.6/en-US/04e64a8ffffe49b8a8a5469796f397c0.html

Code Examples

CDS view ZV_SFLIGHT_CDS:

@AbapCatalog.sqlViewName: 'ZV_SFLIGHT_SQL'
@AbapCatalog.compiler.compareFilter: true
@AbapCatalog.preserveKey: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'CDS view on SFLIGHT'
define view zv_sflight_cds
  as select from sflight
{

  //sflight
  key carrid,
  key connid,
  key fldate,
      price,
      currency,
      planetype,
      seatsmax,
      seatsocc,
      paymentsum,
      seatsmax_b,
      seatsocc_b,
      seatsmax_f,
      seatsocc_f,
      @ObjectModel.readOnly: true
      @ObjectModel.virtualElement: true 
      @ObjectModel.virtualElementCalculatedBy: 'ABAP:ZCL_CDS_FUNCTION'
      cast( '' as abap.char(255)) as text
}

ABAP class ZCL_CDS_FUNCTION:

CLASS zcl_cds_function DEFINITION
  PUBLIC
  FINAL
  CREATE PUBLIC .

PUBLIC SECTION.
 INTERFACES if_sadl_exit_calc_element_read.
PROTECTED SECTION.
PRIVATE SECTION.
ENDCLASS.



CLASS zcl_cds_function IMPLEMENTATION.
  METHOD if_sadl_exit_calc_element_read~calculate.

    DATA:
      lt_calculated_data TYPE STANDARD TABLE OF zv_sflight_cds WITH DEFAULT KEY.

    MOVE-CORRESPONDING it_original_data TO lt_calculated_data.

    LOOP AT lt_calculated_data ASSIGNING FIELD-SYMBOL(<fs_data>).
        <fs_data>-text = 'Awesomeness'.
    ENDLOOP.

    MOVE-CORRESPONDING lt_calculated_data TO ct_calculated_data.

  ENDMETHOD.

  METHOD if_sadl_exit_calc_element_read~get_calculation_info.

  ENDMETHOD.

ENDCLASS.