Anti-pattern in RAP
2023-10-6 22:38:25 Author: blogs.sap.com(查看原文) 阅读量:10 收藏

I’ve been working my way through the excellent opensap.com course, Building Apps with the ABAP RESTful Application Programming Model, when I came across the most egregious anti-pattern built into the very fabric of RAP.

(Fun fact, egregious used to mean really really good. Now it means really really excessively bad).

Week 5 is accessing an external OData service using a Custom Entity.

For some strange reason, parts were working fine until 6pm last night, when suddenly I started getting authentication errors… which were circumvented with the following code:

* https://blogs.sap.com/2019/10/20/how-to-call-a-remote-odata-service-from-the-trial-version-of-sap-cloud-* platform-abap-environment/
   http_client->get_http_request( )->set_authorization_basic(
        i_username = 'ES5 username'
        i_password = 'ES5 password'
    ).

I don’t know, perhaps “they” decided to switch on authentication. Anyway I digress.

What really ticked me off was that when I had finished the app, I discovered that if I didn’t include these calls in my implementation of IF_RAP_QUERY_PROVIDER~SELECT

    io_request->get_requested_elements( ).
    io_request->get_sort_elements( ).

I’d get a dump on the value help for agency ID.

I looked more closely at io_request concrete implementation, and found this:

  METHOD if_rap_query_request~get_sort_elements.
    ms_interface_methods_called-get_sort_elements = abap_true.
    rt_sort_elements = mt_sort_elements.
  ENDMETHOD.

  METHOD ensure_relevant_methods_called.
    TRY.
        IF ms_requested-fill_data = abap_true AND ms_interface_methods_called-get_sort_elements = abap_false AND mt_sort_elements IS NOT INITIAL.
          RAISE EXCEPTION cx_rap_query_not_fully_implmtd=>as_indicated_by_missing_call( co_interface_methods-get_sort_elements ).
        ENDIF.
...

So someone has decided that a GET method, which in any reasonable, rational universe should never have a side effect – if it’s not called, an exception will be raised.

Frankly, I’m morally shocked that such an antipattern has made it into an intrinsic part of RAP.

I’d love to hear the rationale…


文章来源: https://blogs.sap.com/2023/10/06/anti-pattern-in-rap/
如有侵权请联系:admin#unsafe.sh