How Does Spring's @Transactional Annotation Manage Transactions and Handle Self-Invocation?

Unveiling Spring's Transactional Magic

Annotating methods with @Transactional triggers Spring to create a proxy class to intercept incoming method calls. Here's how it works:

Proxy Class Creation and Structure

Spring creates a proxy class that implements the same interfaces as the annotated class. The proxy class is a dynamically generated class that wraps the original class. Inside the proxy class, Spring injects code to handle transactional behavior, such as managing the lifecycle of a transaction.

The actual instance of the original class is not affected. It remains intact, but method calls to the original class are intercepted by the proxy class.

Visibility of Proxy Class

The proxy class is typically invisible at runtime. Spring transparently intercepts method calls through the proxy, making it seem as if the original class is being invoked. However, you can access the proxy class using tools such as debugging tools or AOP frameworks.

Limited Transaction Scope for Internal Calls

Spring's transactional proxies only intercept calls coming from external sources. Calls made within the same object, also known as "self-invocation," are not intercepted. This is because such calls bypass the proxy mechanism.

Self-Invocation Workaround

To enable transactional behavior for self-invocation methods, you can inject an instance of the proxy class into the self-referencing class using a BeanFactoryPostProcessor. This allows you to direct internal calls through the proxy, thus extending the transactional scope to self-invocation methods.

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