Change Data Capture Developer Guide

Change Data Capture
Keep Your External Data Current with Change Data Capture
Change Event Message Structure
Subscribe to Change Events
Subscription Channels
Subscribe with the EMP Connector Sample
Subscribe with Apex Triggers
Change Event Triggers
Apex Trigger Quick Start
Prerequisites
Add an Apex Trigger
Apex Trigger Example
Test Change Event Triggers
Change Event Trigger Considerations
High-Level Replication Steps
Security Considerations
Change Event Considerations
Standard Object Notes
Change Events for Fields
Other Types of Change Events: Gap and Overflow Events
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Add an Apex Trigger

The quick start adds a simple change event trigger that shows how to access header and record fields in a change event message.
Before you add and test the trigger, set up debug logging for the Automated Process entity and enable Account for Change Data Capture. See Prerequisites.
  1. In the Developer Console, select File | New | Apex Trigger.
  2. In the Name field, enter a name for the trigger: MyAccountChangeTrigger.
  3. From the dropdown, select the change event object for Account: AccountChangeEvent.
    The trigger is created with the after insert keyword.
  4. Replace the default content of the trigger with the following code.
    This simple trigger writes header and field values to the debug log for each received change event message. The trigger uses the nulledFields header field to determine if the Phone record field was explicitly set to null in an update operation. The trigger also creates a follow-up task for new accounts.
  5. To test the trigger, create an account with a name and phone.
  6. Edit the account, delete the phone value, and save the record.
  7. In Setup, enter Debug Logs in the Quick Find box, then select Debug Logs.
  8. To view the debug logs corresponding to the record creation, click the second log in the list (logs are ordered by most recent first). The output of the System.debug statements looks similar to the following.
  9. To view the debug logs corresponding to the record update, click the first log in the list. The output of the System.debug statements looks similar to the following. The account name is null because it is unchanged but the phone field was explicitly set to null.