Apex Batch and Scheduled Apex
What is Batch Apex?
Batch Apex is used when you want to process a large number of records (more than 50,000) without hitting governor limits. Salesforce breaks your job into small chunks (called batches), each processed separately.
Why Use Batch Apex?
• To process millions of records without governor limit errors.
• To automate big jobs like data cleanup, report updates, etc.
• To process records asynchronously in the background.
Basic Structure of a Batch Class
You must implement the Database.Batchable interface, which includes:
apex
global class YourBatchClass implements Database.Batchable<SObject> {
global Database.QueryLocator start(Database.BatchableContext bc) {
// Query records to process
}
global void execute(Database.BatchableContext bc, List<SObject> scope) {
// Logic for each batch of records
}
global void finish(Database.BatchableContext bc) {
// Optional – final actions
}
}
Example 1: Update Contact Description Field
Business Logic:
We’ll update all Contact records and set their Description field to “Updated by Batch”.
apex
global class ContactBatchUpdate implements Database.Batchable<SObject> {
global Database.QueryLocator start(Database.BatchableContext bc) {
return Database.getQueryLocator(‘SELECT Id, Description FROM Contact’);
}
global void execute(Database.BatchableContext bc, List<SObject> scope) {
for(SObject s : scope) {
Contact c = (Contact)s;
c.Description = ‘Updated by Batch’;
}
update scope;
}
global void finish(Database.BatchableContext bc) {
System.debug(‘Batch process completed!’);
}
}
To Run:
apex
ContactBatchUpdate batch = new ContactBatchUpdate();
Database.executeBatch(batch, 200); // 200 = batch size
Code Explanation:
• start(): Gets all Contact records.
• execute(): Loops over each batch and updates the Description.
• finish(): Logs a completion message.
Expected Output:
Every contact’s description will be updated to: “Updated by Batch”.
What is Scheduled Apex?
Scheduled Apex lets you run Apex code at a specific time – daily, weekly, monthly, or even hourly.
Structure of a Scheduled Class
apex
global class YourSchedulerClass implements Schedulable {
global void execute(SchedulableContext sc) {
// Logic to run
}
}
Example 2: Schedule the Contact Batch Job
We’ll create a schedule class to run the batch daily at 7:00 AM.
Scheduled Class:
apex
global class ContactBatchScheduler implements Schedulable {
global void execute(SchedulableContext sc) {
ContactBatchUpdate batch = new ContactBatchUpdate();
Database.executeBatch(batch, 200);
}
}
To Schedule the Job:
apex
String cronExp = ‘0 0 7 * * ?’; // Every day at 7 AM
String jobName = ‘Daily Contact Update Batch’;
ContactBatchScheduler sch = new ContactBatchScheduler();
System.schedule(jobName, cronExp, sch);
Cron Expression Breakdown:
| Position | Value | Meaning |
|---|---|---|
| 1 | 0 | Seconds |
| 2 | 0 | Minutes |
| 3 | 7 | Hours (7 AM) |
| 4 | * | Day of month |
| 5 | * | Month |
| 6 | ? | Day of week |
Expected Output:
The Contact batch will automatically run daily at 7 AM and update all contact descriptions.
Best Practices
• Use meaningful names for batch/scheduler classes.
• Limit SOQL queries and DML inside execute.
• Use Test.startTest() and Test.stopTest() in test methods.
• Always handle errors gracefully (try/catch).
Schedule jobs responsibly (avoid job overload).
Test Class Template
For every batch class, write a test like this:
apex
@isTest
private class ContactBatchUpdateTest {
@isTest
static void testBatchExecution() {
// Create sample contacts
List<Contact> contacts = new List<Contact>();
for (Integer i = 0; i < 10; i++) {
contacts.add(new Contact(LastName=’Test’+i));
}
insert contacts;
Test.startTest();
ContactBatchUpdate batch = new ContactBatchUpdate();
Database.executeBatch(batch, 5);
Test.stopTest();
for (Contact c : [SELECT Description FROM Contact]) {
System.assertEquals(‘Updated by Batch’, c.Description);
}
}
}
Practice Tasks
1. Create a batch class that:
- Finds all Account records where Industry is blank.
- Updates the Industry to “Unknown”.
2. Create a batch class that:
- Deletes all Lead records older than 1 year (based on CreatedDate).
3. Create a schedulable class that:
- Schedules the batch from Task 1 to run every Monday at 6:00 AM.
4. Create a batch class that:
- Sends an email to the owner of each Opportunity with Stage = ‘Closed Lost’.
5. Create a batch class to update account rating to “hot”
of all accounts which have annual revenue is more than $3500,000
6. Create a batch class to append account name and opportunity name and store it on a opportunity field
7. Write a batch class to Update Opportunity Stage to “Closed Lost” if the close date is in the past and it’s not already closed.
8. Write a batch class to Automatically update Account Rating based on AnnualRevenue.
Logic:
Revenue > 1M → Rating = ‘Hot’
Revenue 500K–1M → ‘Warm’
< 500K → ‘Cold’
