Dear All,
during implementing OData services and UI5 BSP apps, I was thinking, why we miss a message parameter from the GateWay Data Provider class interfaces? In every ABAP application so far having variety of UIs , we had the possibility to communicate with the users using messages, during data processing/executing actions. This was supported by the SAP standard using any UI so far with built in features. In SAP GUI we can use the message statement, in WebDynpro, we can use the WD framework to display a message, In Floorplan manager, we have the posibility to return BAPI messages also, on every phase of the processing, using interface parameters, so that is displayed on the UI. I know, that OData is a service and protocol,and not a UI.
However every time executing an action(Function Import), which was successful, I have no posssibility to tell the users without additional efforts, which is painful and time-consuming, that the action was successful. We need either fill the HTTP request, and extract it in SAPUI5 manually, or return/read message entities with manual refresh/read from UI5 to the Backend(with multiple roundtrips).
Transferring error messages is no problem of course, you can raise the exceptions above, filling the message container of the exception, and this will be put in the response. But this applicable, when you want to display errors, and not information messages. And I do not see a standard UI5 solution(module/UI5 library) like a cross-application-component to extract exception messages a standard unique way also. What I've seen so far in SAP standard Fiori applications, that SAP developers analyse the HTTP response manually, and differently to extract error information from request somehow. This extraction varies per application.
As per my understanding filling the HTTP response with message data is not against the OData protocol, so it would be great if we could have an ET_MESSAGE parameter for example and fill it with any business message. On the UI side it could be combined automatically with one of the two controls below:
of course with no additional costs to extract messages, bacause this would be supported by the UI5 library itself, we would just need to configure the application component to use the message area or not.
This improvement or a solution like this, what fits to the SAP GateWay and UI5 control library (where separation of UI and service properly keeping the standards) is needed not only at customer side, but SAP internally also. I saw a lot of different javascript coding to extrcat messages in SAP UI5 apps, with comments like this: "TO-DO: nice error popup" etc. So this is pain and extra cost/each application SAP internally also.
If someone from SAP GateWay or UI5 Product Management reading this, is it possible to put this on a requirement list ? 
I do not want to restrict the UI5 library to SAP GateWay only, but having at least two standard helper classes would be great both at UI and Backend side to fill in and extract the response.
Is anyone else who votes for this ?
Thanks, Attila