When you annotate a method with the @Transactional annotation in Spring, several key processes occur to manage the transactional behavior of that method, ensuring that the operations within the method are executed within a transaction context. Here's a detailed breakdown of what happens:
1. Proxy Creation
Spring uses a proxy-based approach to manage transactions. When a class or a method is annotated with @Transactional, Spring dynamically creates a proxy around the object. This proxy is responsible for the management of the transactional behavior[9].
2. Transactional Advice
The proxy includes transactional advice, which is code that Spring injects before and after the method execution. This advice controls the transaction behavior. When a method annotated with @Transactional is called, the transactional advice first checks if there is an existing transaction. If not, it starts a new transaction[9].
3. Method Execution
Once the transaction is started (or an existing transaction is used), the method execution proceeds. All operations performed within the method are part of this transaction. This means that any changes to the database or any other transactional resource are held in a pending state, not yet committed[9].
4. Commit or Rollback
After the method execution:
If the method completes successfully without throwing any exceptions, the transactional advice commits the transaction, making all changes permanent.
If an exception is thrown, the transactional advice determines whether it should trigger a rollback. By default, runtime exceptions cause the transaction to roll back, but this behavior can be customized using the rollbackFor and noRollbackFor attributes of the @Transactional annotation[9].
5. Transaction Propagation
The @Transactional annotation also supports various propagation behaviors, which define how transactions are handled in relation to each other. For example, PROPAGATION_REQUIRED will use an existing transaction if available; otherwise, it starts a new one. This is configurable through the propagation attribute of the annotation[9].
6. Limitations and Considerations
Proxy Limitation: The transactional proxy only intercepts external method calls coming through the proxy. Calls within the same class to ...
