When might the @Transactional annotation not work?

The @Transactional annotation in Java may not work in the following cases:

1. Calling a method with @Transactional within the same class — if the annotated method is called directly from another method of the same class, Spring's proxy will not intercept the call, and a transaction will not be created.

2. The method is not public — by default, Spring creates proxies for public methods; if the method is private or protected, the annotation may not work.

3. Lack of transaction configuration — if Spring is not configured to support transactions (for example, if @EnableTransactionManagement is not enabled), the annotation is ignored.

4. Exceptions that do not trigger rollback — by default, transactions rollback only on unchecked exceptions (RuntimeException). If a checked exception is thrown, rollback will not occur unless explicitly specified.

5. Using @Transactional on interface methods without CGLIB proxy — if the proxy is created via JDK dynamic proxies and the method is not declared in the interface, the annotation may not work.

Example of a problem with internal class call:

@Service
public class MyService {

    @Transactional
    public void transactionalMethod() {
        // ...
    }

    public void nonTransactionalMethod() {
        transactionalMethod(); // call within the class, transaction will not be created
    }
}