SAP GW - Implement a better OrderBy for Cust EXT Class

[alex_geppart]

Intro

If you have defined your OData Service in transaction SEGW and use the own class (* _DPC_EXT) for Service Implementation,

you may have asked yourself how to use the parameter IT_ORDER of Type  /IWBEP/T_MGW_SORTING_ORDER to implement sorting of your entity table.

One way could be to use standard GW util class  /IWBEP/CL_MGW_DATA_UTIL and its method orderBy.

But by using this, it might happen that you stumble upon a constraint where you get an exception if you use a parameter in your orderBy clause which has a underline in its name definition.

For example you would use this URL where StartDate is the attribute you want to sort descending:

/sap/opu/odata/sap/<YOUR_SERVICE_NAME>/ProjectSet?$orderby=StartDate%20desc

The Problem is that 'StartDate' is the attribute name of your gateway service entity and in you backend table it could have the name 'START_DATE'.

so  'StartDate' <> 'START_DATE'

Because of the standard implementation of  method orderBy you will get an Error : "RFC Error: Incorrect value in the dynamic table."

HowTo

To get arround this pittfall you could use your own util class to sort the table.

Where you can use o_tech_request_context object.

This object does the mapping to get the corresponding database field name (see comment of Ron).

It could look like this:

IT_ORDER    TYPE  /IWBEP/T_MGW_TECH_ORDER    "*the sorting order

CT_DATA      TYPE STANDARD TABLE   " * CT_DATA is your Entetyset table returning just after the select from db.  

METHOD orderby.

   DATA: lt_otab   TYPE abap_sortorder_tab,

              ls_oline  TYPE abap_sortorder.

   DATA: ls_order LIKE LINE OF it_order.

   CONSTANTS:BEGIN OF lcs_sorting_order,

                             descending TYPE string VALUE 'desc',

                            ascending  TYPE string VALUE 'asc',

             END OF   lcs_sorting_order.

LOOP AT it_order INTO ls_order.

     ls_otab-name = ls_order-property.

     IF ls_order-order = lcs_sorting_order-descending.

       ls_otab-descending = abap_true.

     ELSE.

       ls_otab-descending = abap_false.

     ENDIF.

     APPEND ls_otab TO lt_otab.

ENDLOOP.

   SORT ct_data BY (lt_otab).

ENDMETHOD.

And you can use this method like this:

IF it_order[] IS NOT INITIAL.

     "* get technical names for order table

     DATA: lt_tech_order TYPE /iwbep/t_mgw_tech_order.

     lt_tech_order = io_tech_request_context->get_orderby( ).



     zcl_cl_util=>orderby(

     EXPORTING

       it_order =  lt_tech_order   " the sorting order

     CHANGING

       ct_data  =   et_feed

   ).



 ENDIF.