What is the principle behind the implementation of Spring transactions?

The main aspects involved in the implementation principles of Spring transactions include:

1. Transaction Manager: In Spring, transactions are managed uniformly by the transaction manager, which can be provided by frameworks like JDBC, JPA, Hibernate, or by Spring itself. The transaction manager is responsible for starting, committing, or rolling back transactions.
2. Transaction Definition: Defining transaction boundaries and attributes such as isolation level, propagation behavior, and read-only through annotations like @Transactional or XML configurations.
3. Proxy pattern: Spring uses the proxy pattern in Aspect-Oriented Programming (AOP) to implement transactions. When a method is marked as a transactional method using the @Transactional annotation or XML configuration, Spring encapsulates the method invocation in a proxy object, adding transaction management logic such as beginning a transaction before the method executes and committing or rolling back the transaction after the method executes.
4. Transaction aspect: Spring integrates transaction management logic into target objects using AOP. In Spring, transaction aspects can be configured using either a configuration-based approach (such as XML configuration) or an annotation-based approach (such as the @Transactional annotation).
5. Transaction synchronization and binding: Spring uses the ThreadLocal mechanism to bind a transaction to the current thread, ensuring that multiple transaction operations within the same thread use the same transaction.

In general, the implementation principle of Spring transactions is to use proxy pattern and AOP to weave transaction management logic into the target object. The transaction manager is responsible for managing the beginning, submission, or rollback of transactions, while using the ThreadLocal mechanism to ensure the binding of transactions to the current thread. This allows developers to focus on business logic without having to explicitly write transaction management code, thereby improving code maintainability and reusability.