How to conditionally control the execution of execute() method from the start() method of a batch class

Question

I'm making a call out to get an auth token in the start() method of my batch class (I'm implementing the stateful interface and using a class variable to save this token for the entire batch transaction). Here's a simplified version of my start method.

public Database.QueryLocator start(Database.BatchableContext bc)
{
    // Retry for token
    Boolean receivedToken = false;
    Integer retryCount = 0;
    do
    {
        receivedToken = Helper.getAuthToken();
        retryCount++;
    }
    while (!receivedToken && retryCount <= 3);

    if(receivedToken)
    {
        this.AUTH_TOKEN = Helper.AUTH_TOKEN;
    }
    else
    {
        // Returning an empty result
        return Database.getQueryLocator('SELECT Id FROM Custom_Object__c WHERE CreatedDate = TOMORROW');
    }

    return Database.getQueryLocator(this.QUERY);
}

My intention is to avoid the execution of the execute() method when the auth token request fails, but still allow the finish() method to process all of its logic. As you see I'm making a query that I know will return an empty result in all situations and this is working fine, But is this proper the way to do this? I've also posted this comment here which might help someone with a slightly different situation.

I appreciate any suggestions! 🍻

Answer 1

You could actually just:

public Iterable<Custom_Object__c> start(Database.BatchableContext bc)

And if you don't want any execution to occur:

return new Custom_Object__c[0];

This returns an empty list, so no execute call will happen, and you don't need a query. Note that you'll have to cast the QueryLocator to use this technique:

return (Iterable<Custom_Object__c>)Database.getQueryLocator(this.QUERY);