Also, you may consider using the HttpBuilder script utility. Then you can have the whole thing in a scripting data source, clean and tidy.

There is documentation in the contextual help menu for "Mango Java Script" (which you can access through the scripting help, or the meta point help).

Here's a thread where I posted something maybe more complex than what you're talking about: https://forum.infiniteautomation.com/topic/2999/intesis-integration

It sounds like yours may be as simple as...

var headers = {}
var parameters = {}
function handleTemperatureData(data) { /* Do stuff */ }
HttpBuilder.get("https://someplace.wherever", headers, parameters).err(function(status, headers, content) {
  throw "Script failed with HTTP status: " + status;
}).resp(function(status, headers, content) { //needs to be 200 status or you can set the accepted statuses
  handleTemperatureData( JSON.parse(content) );
}).execute();

Both those should work. If you alphanumeric matches the whole response you can do something like var response = JSON.parse(alphanum.value); and then you can process it however you like. Then trigger the script on the context update of the alphanumeric point.