In Salesforce the same bit of code can be triggered a lot of different ways and with calls to third parties there are different rules for the different ways of calling stuff.
For example take this bit of code, in it we are just passing a contact ID and it is going to go and talk to a third party web service, inside the “setUpRequest” it’s going to update the third party with the details of the Salesforce Contact and in return recive some bits and bobs from the third party to update the Saleforce side. Basic syncing between two parties
we want this thing to happen at two different times:
So this bit of code has to be callable both from a Schedule and from a save Trigger
let’s take the save trigger first, as it is now it won’t work, you will get the error “Callout from triggers are currently not supported.” error if you try, normally you would just pop the annotation “@Future(callout=true)”1 at the top of this function and that would solve that but as you will see later on we can’t do that so what we’re going to do is have a little wrapper function that has the @future annotation and from that it’s going to call are real function.
we can then put that wrapper functions in our contact save trigger and everything will work perfectly
Next comes calling it from a schedule, if we had put the @future annotation on the actual function this would fail because you cannot call a future function from a scheduled action but we dont have that issue now, what you DO have to do is bolt-on the “Database.AllowsCallouts” to your batch object as seen below
Now your batch object will be allowed to do callouts.
Putting all these bits together means you can have a single function that calls out to third parties that can be triggered from either a Schedule or an ordinary Trigger.
The “@Future(callout=true)” annotation basically means that the salesforce code does not stop and wait before doing other things this means that calls to third parties does not slow down the salesforce UI. ↩