HTTP request to an external web resource

Ancestors - Object (PRIM_OBJT)

Details

An HTTPRequest allows access to 3rd party HTTP services, allowing LANSA to integrate with other web services.
 
An HTTPRequest is effectively a standard XMLHttpRequest in JavaScript.
 
HTTPRequests should be defined within the routine in which they are going to execute. This will create a new instance every time one is executed. The corresponding event routines for the Completed and Failed events are coded in the same routine.
 
The LANSA runtime maintains the instances until they have finished. This allows the same routine to be executed many times, and many requests to be performed, each one independently producing results.
 
If the HTTPRequest exists as a global scope, there will only ever be one instance, meaning multiple requests may interfere with each other.
 
Therefore, HTTPRequest instances should not be defined within an EVTROUTINE as event routines cannot have other child event routines to handle the Completed and Failed events. Define and call the HTTPRequest instance in a method routine, which is called from the event routine instead.

Example

In this example, a weather API is executed asynchronously, returning the data as a JSON object.
 
When the completed event fires, the result is processed.

Mthroutine Name(GetWeather) Access(*PRIVATE)
Define_Map For(*INPUT) Class(#Prim_Str) Name(#Resource)

Define_Com Class(#PRIM_WEB.HttpRequest) Name(#Request)
Define_Com Class(#PRIM_WEB.Json) Name(#Json)

#Request.Url := "http://api.openweathermap.org" + #Resource

#Com_owner.UpdateForPending

#Request.ExecuteAsync

Evtroutine Handling(#Request.Completed)

If (#Request.Response *IsNot *null)

Case (#Request.Response.StatusCode)
When (= 200)

#Json := #Request.Response.Content
#Com_owner.Update( #Json.RootItem )

Otherwise

#Com_owner.UpdateForFailure( #Request )

Endcase

Endif

Endroutine

Endroutine

Properties

Events

Methods

See also

All Component Classes

Technical Reference

Febuary 18 V14SP2