Schlagwort: REST

Piyush Philip auf sap.com hat eine simple Möglichkeit beschrieben, wie man in ABAP einen REST-Service mit den entsprechenden CRUD-Methoden implementieren kann. Dazu ist im Wesentlichen nur eine eigene Handler-Klasse zu implementieren, die von IF_HTTP_EXTENSION erbt. Diese Handler-Klasse wird von einem Service des ICF gerufen.

1. SE80 -> Neue Klasse anlegen
2. In der Klasse im Reiter Interfaces: vom Interface IF_HTTP_EXTENSION erben
3. die Interface-Methode IF_HTTP_EXTENSION~HANDLE_REQUEST implementieren (implementiert nur REST, kein OData-Sevice!)

   METHOD if_http_extension~handle_request.
   
   * Typen
       TYPES: BEGIN OF ty_json_request,
                param1 TYPE char64,
                param2 TYPE char64,
              END OF ty_json_request.
   
       TYPES: BEGIN OF ty_json_response,
                success   TYPE string,
                msg       TYPE string,
                operation TYPE string,
              END OF ty_json_response.
   
   * Variablen
       DATA: rv_response TYPE ty_json_response.
       DATA: it_path_info TYPE stringtab.
       DATA: it_query_strings TYPE stringtab.
   
   * Header Fields auslesen
       DATA: it_header_fields TYPE tihttpnvp.
       server->request->get_header_fields( CHANGING fields = it_header_fields ).
   
   * Request Methode (POST, GET, PUT, DELETE ...)
       DATA(lv_request_method) = server->request->get_header_field( name = '~request_method' ).
   
   * URL Pathinfo
       DATA(lv_path_info) = server->request->get_header_field( name = '~path_info' ).
   * erstes '/' entfernen
       SHIFT lv_path_info LEFT BY 1 PLACES.
       SPLIT lv_path_info AT '/' INTO TABLE it_path_info.
   
   * URL Parameter (Query Strings) für Auswertung
       DATA(lv_query_string) = server->request->get_header_field( name = '~query_string' ).
       SPLIT lv_query_string AT '&' INTO TABLE it_query_strings.
   
   * Request Methoden behandeln
       CASE lv_request_method.
   * C (Create)
         WHEN 'POST'.
   * Beispiel: per Request übermittelte JSON-Daten auslesen und behandeln
   * Content-Typ auslesen
           DATA(lv_request_content_type) = server->request->get_content_type( ).
   
   * Wenn Content-Typ JSON
           IF lv_request_content_type CP if_rest_media_type=>gc_appl_json.
   * JSON-Daten auslesen und nach ABAP-Typ konvertieren -> Parameternamen müssen übereinstimmen, sonst HTTP 500!
             DATA(lv_request_cdata) = server->request->get_cdata( ).
   
             DATA: lv_request_abap TYPE ty_json_request.
   
             TRY.
                 /ui2/cl_json=>deserialize( EXPORTING json = lv_request_cdata
                                                      pretty_name = /ui2/cl_json=>pretty_mode-camel_case
                                            CHANGING  data = lv_request_abap ).
   
               CATCH cx_root INTO DATA(e_txt).
                 MESSAGE e_txt->get_text( ) TYPE 'S' DISPLAY LIKE 'E'.
             ENDTRY.
   
             rv_response = VALUE #( success   = 'true'
                                    msg       = lv_request_abap-param1 && ' | ' && lv_request_abap-param2
                                    operation = lv_request_method ).
           ELSE.
             rv_response = VALUE #( success   = 'false'
                                    msg       = 'Request content type must be application/json'
                                    operation = lv_request_method ).
           ENDIF.
   * R (Read)
         WHEN 'GET'.
           DATA(lv_param) = server->request->get_form_field( 'param' ).
   
           rv_response = VALUE #( success   = 'true'
                                  msg       = lv_param
                                  operation = lv_request_method ).
   * U (Update)
         WHEN 'PUT'.
           rv_response = VALUE #( success   = 'true'
                                  msg       = ''
                                  operation = lv_request_method ).
   * D (Delete)
         WHEN 'DELETE'.
           rv_response = VALUE #( success   = 'true'
                                  msg       = ''
                                  operation = lv_request_method ).
   
   * unerlaubte Methoden abfangen
         WHEN OTHERS.
   * Fehlercode 405 zurückgeben
           server->response->set_status( code   = cl_rest_status_code=>gc_client_error_meth_not_allwd
                                         reason = 'method not allowed' ).
   
           server->response->set_content_type( if_rest_media_type=>gc_appl_json ).
   
           server->response->set_header_field( name  = if_http_header_fields=>allow
                                               value = 'POST,GET,PUT,DELETE' ).
   
           rv_response = VALUE #( success   = 'false'
                                  msg       = 'error'
                                  operation = lv_request_method ).
       ENDCASE.
   
   * wenn erfolgreich, dann Wert zurückgeben
       IF rv_response-success = 'true'.
   * HTTP-Status 200
         server->response->set_status( code   = cl_rest_status_code=>gc_success_ok
                                       reason = 'Ok.' ).
   
   * application/json
         server->response->set_content_type( if_rest_media_type=>gc_appl_json ).
   
   * Service-Response als JSON zurückgeben
         server->response->set_cdata( data = /ui2/cl_json=>serialize( data        = rv_response
                                                                      pretty_name = /ui2/cl_json=>pretty_mode-camel_case ) ).
   
       ENDIF.
   
   ENDMETHOD.
   

4. SICF -> neue ICF-Node (Sub-Element) unterhalb default_host -> sap -> bc als neuen unabhängigen Service anlegen
5. in der Handlerliste des Service die erstellte Klasse als „Handler“ angeben
6. auf die neue ICF-Node rechtsklicken -> Service aktivieren
7. auf die neue ICF-Node rechtsklicken -> Service testen
8. URL aus Browserfenster kopieren (http://domain.de/sap/bc/servicename?sap-client=900)
9. im Browser mir einem Rest-Plugin (FireFox-Prugin: Rested) testen

Links

• https://blogs.sap.com/2018/10/31/a-simple-rest-web-service-from-ecc-called-from-a-html5-screen/
• https://blogs.sap.com/2012/12/07/building-a-crud-application-with-sapui5-and-icf-restjson-service-part-1/
• https://blogs.sap.com/2013/01/24/developing-a-rest-api-in-abap/
• https://medium.com/pacroy/developing-apis-in-abap-just-rest-not-odata-d91cf899f7d3
• https://blogs.sap.com/2013/05/16/usage-of-the-abap-rest-library-sapbasis-740/
• https://www.linkedin.com/pulse/create-json-rest-service-from-sap-back-end-louis-rossi-mundecke
• REST Interfaces and Classes
• The GET Method
• The POST Method
• The PUT Method
• The DELETE Method