Tell me about the propagation types in the @Transactional annotation. Have you ever set non-default ones?

The @Transactional annotation in Spring has a propagation parameter that determines how a transaction should behave when a method is called within an existing transaction.

Main types of propagation:

• REQUIRED (default): if there is a current transaction, the method runs within it; otherwise, a new one is created.
• REQUIRES_NEW: always creates a new transaction, suspending the existing one.
• SUPPORTS: if a transaction exists, use it; otherwise, execute without a transaction.
• NOT_SUPPORTED: always execute without a transaction, suspending the existing one.
• MANDATORY: must be called within a transaction; otherwise, an exception is thrown.
• NEVER: must be called outside a transaction; otherwise, an exception is thrown.
• NESTED: if a transaction exists, create a nested (savepoint) transaction; otherwise, behave like REQUIRED.

Using non-default propagation is useful when you need to control transaction boundaries, for example:

• REQUIRES_NEW for independent operations so that errors in them do not roll back the main transaction.
• NESTED for partial rollback within a large transaction.

Example:

@Transactional(propagation = Propagation.REQUIRES_NEW)
public void saveAudit() {
    // save audit independently of the main transaction
}