Java: Inversion of Control (IoC)

By using proxies to handle transaction boundaries.

Transaction self-invocation occurs when a method within the same class calls another method annotated with @Transactional. Spring Boot uses proxies to manage transaction boundaries. Without proxies, the transactional method would not initiate a transaction if called internally. For example, in an e-commerce service, if a method `processOrder()` internally calls `chargeCustomer()` which is transactional, Spring’s proxy will ensure `chargeCustomer()` executes within a transaction even when invoked internally.