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.

Error Results

If the result is an error response (400-599 HTTP Error Codes) you can check lError and cErrorMsg. If the error result includes JSON and a .message or .Message property that value is set for the error message.

Errors return a Response Value

Note that 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. So if you get a 401 (Not Authorized) and the server sends a JSON object response with error info, you get that object back.

The bottom line is: You always need to check the .lError flag or check the `. to ascertain whether the req

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

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, 1996-2019 • Updated: 04/18/19
Comment or report problem with topic