Scheduled Apex, Callouts and Running a Batch

Question

I don't think what I am trying to do can be done with my current setup, but before I embark on some rework, I just wanted to check I haven't missed an approach...

I have a scheduled class that executes a batch. So far so good. But to run that batch, I need to check a date from an external web service to include in the SOQL - and this is where I am running into a problem. A scheduled class can only make a callout if the callout is run in an @future context. But sadly, a class running as @future can't then execute a batch, or even schedule a batch to run in the future using system.schedulebatch. So is there any approach that would let me schedule a class to make a callout, and then also execute/schedule a batch that I am missing? Right now, I am thinking I need my scheduled class to make the callout via @future and have the @future update a custom setting with the results, and have the scheduled class also schedule a class to execute my batches run in x mins to allow time for @future to run?

Answer 1

Why not just perform the callout in your Batch Apex start method? This means you will always start the Batch Apex job from your Scheduled apex job, but i think is on balance better than having to marshall schedule jobs between @future jobs?

public with sharing class BatchWithCallout 
   implements Database.Batchable<SObject>, Database.AllowsCallouts 
{
    public Database.QueryLocator start(Database.BatchableContext BC) 
    { 
        // Callout for Date
        HttpRequest request = new HttpRequest();
        request.setEndpoint('http://www.timeapi.org/pdt/next+monday');
        request.setMethod('GET');
        Http http = new Http();
        HttpResponse response = http.send(request);
        String dateValue = response.getBody();
        List<String> dateParts = dateValue.split('T');

        // Query with date returned
        return Database.getQueryLocator(
              'select Id from Opportunity where CloseDate < ' + dateParts[0]); 
    }

    public void execute(Database.BatchableContext info, List<SObject> opportunities) {}

    public void finish(Database.BatchableContext info) { }
}