wwJsonServiceClient::CallService

Calls a REST service that returns and optionally expects JSON data. The JSON data is returned as a FoxPro simple value, object or collection.

Parameter Inputs

To call a service you specify the HTTP Verb, plus any optional data to send to the service. You can only pass a single value that is serialized to JSON, but this value can be an object that contains many nested sub-objects or collections. REST services in general accept only a single data object which can contain mutliple sub-objects that act as parameters. How this is set up depends on the service however.

Return Values

This method expects the service to return a JSON response (application/json content type) which is turned into a FoxPro value, object or collection that is returned as part of this method.

Errors always return a Response Value: Check .lError!

CallService() always returns some sort of response - either a string of the raw HTTP buffer, or if the data is application/json content, the deserialized JSON object. This happens even if an error occurred and the response contains an error.

So if you get something like a 401 - Not Authorized response and the server sends a JSON object response with error info, you get the error object back. IOW, the response won't be null or empty, but that object.

The bottom line is: To check for success of a request, You should always check the .lError flag and .cErrorMsg to ascertain whether the request succeeded.

o.CallService(lcUrl,lvData,lcVerb)

Parameters

lcUrl
The URL to access the service method on the server

lvData
Optional - A FoxPro value or object or collection that is serialized to JSON and sent to the server

lcVerb
Optional - The HTTP Verb to use for this request (GET,POST,PUT,DELETE,HEAD,OPTIONS etc.). Default is GET if no data is sent or POST if lvData is not null or empty.

Example


        foxpro
        
            
        
     

        foxpro
        
            
        
     
loProxy = CREATEOBJECT("wwJsonServiceClient")

lcUrl = "http://albumviewer.west-wind.com/api/album"
lvData = loAlbum && FoxPro object
lcVerb = "PUT"   && HTTP Verb

*** Make the service call and returns an Album object
loAlbum = loProxy.CallService(lcUrl,lvData,lcVerb)

IF (loProxy.lError)
   ? loProxy.cErrorMsg
   RETURN
ENDIF   

? loAlbum.Title
? loAlbum.Artist.ArtistName