CDS Custom entities with Association

[72593028]

Step 1- Create a CDS Root Custom Entity for the Header (using Eclipse tool)

Start by creating a root custom entity for the PO Header entity. This entity will have an      association to the PO Items.

@ObjectModel.query.implementedBy:'ABAP:YCL_MM_PO_DETAILS'
@EndUserText.label: 'Header data'
define root custom entity YMM_PO_HEADER
// with parameters parameter_name : parameter_type
{
  key EBELN : ebeln;
      BUKRS : bukrs;
      BSTYP : ebstyp;
      BSART : esart;
      LOEKZ : loekz;
      _Items : composition[1..*] of YMM_PO_ITEM;
}

 Step 2- Create a CDS  custom entity for Item

Next, create a custom entity for PO Item. The Item entity will reference the Header entity using an association.

@ObjectModel.query.implementedBy:'ABAP:YCL_MM_PO_DETAILS'
@EndUserText.label: 'PO Item'
define custom entity YMM_PO_ITEM
// with parameters parameter_name : parameter_type
{
  key EBELN : ebeln;
  key EBELP : ebelp;
      MATNR : matnr;
      @Semantics.quantity.unitOfMeasure: 'MEINS'
      MENGE : bstmg;
      MEINS : bstme;
      @Semantics.amount.currencyCode: 'currency'
      NETPR : bprei;
      @Semantics.currencyCode
      currency : abap.cuky( 5 );
      _Header : association to parent YMM_PO_HEADER  on $projection.EBELN = _Header.EBELN;
}

 Step 3- Create a your own Custom class which you mentioned in Entity 

Now, create a custom ABAP class to implement the functionality behind your CDS          entities. The class will implement the necessary interfaces.

 @ObjectModel.query.implementedBy:'ABAP:YCL_MM_PO_DETAILS'

 interfaces IF_OO_ADT_CLASSRUN .
  interfaces IF_RAP_QUERY_PROVIDER .

Step 4- Implement the class

class YCL_MM_PO_DETAILS definition
  public
  final
  create public .

public section.


     types : begin of ty_header,
              EBELN type ebeln,
              BUKRS type bukrs,
              BSTYP type ebstyp,
              BSART type esart,
              LOEKZ type loekz,
             end of ty_header.

      data : lt_header type table of ty_header.

          types : begin of ty_item,
              EBELN type  ebeln,
              EBELP type ebelp,
              MATNR type matnr,
              MENGE type bstmg,
              MEINS type bstme,
              NETPR type bprei,
             end of ty_item.

      data : lt_item type table of ty_item.


  interfaces IF_OO_ADT_CLASSRUN .
  interfaces IF_RAP_QUERY_PROVIDER .
protected section.
private section.
ENDCLASS.



CLASS YCL_MM_PO_DETAILS IMPLEMENTATION.


  method IF_OO_ADT_CLASSRUN~MAIN.
  endmethod.


  method IF_RAP_QUERY_PROVIDER~SELECT.


     CASE io_request->get_entity_id( ).

   when 'YMM_PO_HEADER'.

   DATA(lt_parameters) = io_request->get_parameters( ).

   DATA(lv_offset) = io_request->get_paging( )->get_offset( ).
   DATA(lv_page_size) = io_request->get_paging( )->get_page_size( ).
   DATA(lv_header_filter) = io_request->get_filter( )->get_as_sql_string( ).

     DATA(lv_max_rows) = COND #( WHEN lv_page_size = if_rap_query_paging=>page_size_unlimited
                                THEN 0
                                ELSE lv_page_size ).

   select * from ekko
          where (lv_header_filter)
          order by EBELN
          into corresponding fields of table _header
         up to _max_rows  rows
         offset _offset.

* IF io_request->is_total_numb_of_rec_requested( ).
    io_response->set_total_number_of_records( lines( lt_header ) ).
 io_response->set_data( lt_header ).
* endif.

 when 'YMM_PO_ITEM'.

    DATA(lt_para_item) = io_request->get_parameters( ).

   DATA(lv_offset_item) = io_request->get_paging( )->get_offset( ).
   DATA(lv_page_size_item) = io_request->get_paging( )->get_page_size( ).
   DATA(lv_item_filter) = io_request->get_filter( )->get_as_sql_string( ).

     DATA(lv_max_rows_item) = COND #( WHEN lv_page_size_item = if_rap_query_paging=>page_size_unlimited
                                THEN 0
                                ELSE lv_page_size_item ).

   select * from ekpo
          where (lv_item_filter)
          order by EBELN
          into corresponding fields of table _item
         up to _max_rows  rows
         offset _max_rows_item.

    io_response->set_total_number_of_records( lines( lt_item ) ).
 io_response->set_data( lt_item ).

   endcase.


  endmethod.
ENDCLASS.

Note- If your Item entity is not getting triggered possibly you might have missed filter .

Step 5- Create Service definition for your root view entity and expose you entities

->Right click on your root view entity->Click new service definition

@EndUserText.label: 'Po Details'
define service YMM_PO {
  expose YMM_PO_HEADER as Header;
  expose YMM_PO_ITEM as Item;
}

Step 6- Create Service binding for your service definition

After defining the service, create a service binding to make the service available for consumption.

• Right-click on your service definition and select New Service Binding.
• Activate the service.

If your service is an OData V4 service, you may encounter issues during publishing. For assistance with publishing and activating your service, refer to this

https://community.sap.com/t5/technology-blogs-by-members/publish-activate-an-odata-v4-service-group-...

Step 7- Test the GET Call with Association

Finally, test your service by making a GET request to retrieve the Header and Item details as a nested JSON structure.

Note- If you want to pass the URL with key value

Header('value')?$expand=_Items

If you're interested in consuming this data in RAP with a tree structure using Flexible Programming Model (FPM), feel free to reach out.

Enjoy Coding!

Thanks and Regards,
Thulasiram Ammati