wwJsonServiceClient::CallService
about 1 minute to read

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
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

See also:

Class wwJsonServiceClient

© West Wind Technologies, 1996-2025 • Updated: 01/14/25
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