Can we do a callout inside for loop in batch class

Question

Callout class

Public class calloutValidation{
    public static string CalloutCheck(String Email{
        try{
        //There are some logic 
            HttpRequest req = new HttpRequest();
            HttpResponse res = new HttpResponse();
            req.setMethod('POST');
            req.setEndpoint('callout:xxx');
            req.setHeader('Content-Type', 'application/json');
            req.setHeader('xxx', 'xxx');
            req.setBody(reqBody);
            System.debug(req);
            System.debug(req.getEndpoint());
            if (!Test.isRunningTest()) {
                res = new http().send(req);
                System.debug(res);
            }
            return res.getBody();
        }
        catch(CalloutException exp){
            return exp.getMessage();
        }
    }
}

Batch class

public with sharing class xxxx implements Schedulable, Database.Batchable<sObject> {
    public Database.QueryLocator start(Database.BatchableContext bc) {
        return 'select id,Email from Contact Where Email != null';
    }
    
    public void execute(Database.BatchableContext bc, List<Contact> contactList){
        // process each batch of records
        EmailStatusValidationQueueable Queueable = new EmailStatusValidationQueueable(contactList);
        System.enqueueJob(Queueable);

    }

    public void finish(Database.BatchableContext bc){

    }

public with sharing class EmailStatusValidationQueueable implements Queueable,Database.AllowsCallouts {
public List<Contact> contactList;
public EmailStatusValidationQueueable(List<Contact> conList){
    contactList = conList;
    System.debug('contactList EmailStatusValidationQueueable: ' +contactList);
}
public void execute(QueueableContext context) {
    // awesome code here
    Integer sentCount = 0;
    Boolean hitLimit = false;
    List<Contact> updateContact = new List<Contact>();
    for (Contact con : contactList) {
        if (Limits.getCallouts() == Limits.getLimitCallouts()) {
            hitLimit = true;
            break;
        }

        // Do your callout
        String res= calloutValidation.CalloutCheck(con.Email);
        System.debug('res : ' +res);
        if(res != null){
            Map<String, Object> resultJsonData = (Map<String, Object>)JSON.deserializeUntyped(res);
            System.debug('resultJsonData: ' +resultJsonData);
            if(resultJsonData.get('message') != null  && resultJsonData.get('message') == 'OK'){
                con.xxxx = 'Validated';
                System.debug('resultJsonData success');
                updateContact.add(con);
                System.debug('updateContact ' +updateContact);
            }else{
                System.debug('resultJsonData Fail');
            }
        }
        // Track how many leads have been processed
        sentCount++;
    }

    List<Database.SaveResult> result = Database.update(updateContact, false);
    system.debug('result '+result);

    for (Database.SaveResult r : result)

    {
        if (!r.isSuccess())
        {
            system.debug('not isSuccess ');
            for (Database.Error e : r.getErrors())
            {
                system.debug('Error'+e);
            }
        }
    }

    if (hitLimit) {
        // Need to chain this queueable to finish processing. First clean up
        // the list of leads needing a callout, removing all those that have
        // been sent already
        for (Integer index = 0; index < sentCount; index++) {
            contactList.remove(0);
        }

        // Now ensure the remainder get processed by simply re-enqueuing this
        // queueable with its adjusted state
        System.enqueueJob(this);
    }


}

}

1. There is a batch class which will take all email in contact .(org have more than 4 lakh) Then from that batch class I need to pass each of email to this calloutValidation class and do the Api callout.(Because Post body support only one email at a time)

2. Can I do a for loop inside execute() method in batch and call the callout class by passing each contact email? Updated--->this only execute 7 records

callout inside for loop This is similar but I need support how can i apply that to my one.

Answer 1

I would suggest that your batchable execute() pass the list of objects to a Queueable class (via its constructor)

• The queueable class would take the first object off the list
• Make the callout and do whatever DML is required
• Enqueue the Queueable class again, passing to its constructor the list of objects minus the object just processed.

Then your batchable execute() method can process 200 objects per transaction but each queueable does only one callout and so would not be subject to a Limits exception on # of callouts or total time for all callouts

There are more sophisticated versions of this pattern

• Dan Applemen Advanced Apex Going Asynchronous Chapter
• @PhilW Governor Friendly Asynchronnous Processing from Triggers (which can be adpated for batchables)