英文:
How can I see the class proxy code in Spring Framework?
问题
我想查看Spring中的Transactional注解在运行时生成的代码。我该如何做？
如果这不可能或者难以实现，请告诉我Spring在带有Transactional注解的方法中插入了什么代码。我知道在事务中应该使用entityManager.getTransaction().begin();和entityManager.getTransaction().commit();来使用EntityManager。但是在多线程环境中，当许多线程访问同一个EntityManager并调用entityManager.getTransaction().begin();时，它是如何工作的？如果事务已经打开，将会抛出异常。因此，如果Spring确实将这些带有事务的代码插入到方法中，它在多线程环境中是如何工作的？
英文:
I want to see what code is generated on the fly by Transactional annotation in Spring. How can i do this?
If this is impossible or difficult to do, then please tell me what code Spring inserts into the methods annotated with Transactional annotation. I know that using EntityManager in transactions should be used entityManager.getTransaction().begin(); and entityManager.getTransaction().commit();. But how does it work in a multi-threaded environment, when many threads access the same EntityManager and call entityManager.getTransaction().begin();? If a transaction has been opened, an exception will be thrown. Therefore, if Spring inserts exactly this code with transactions into methods, how does it work in a multithreaded environment?
答案1
得分: 1
代理代码没有生成。实际上，这些是一些实现了 InvocationHandler 的静态代码。有关它是如何工作的示例，请参见此链接。
在Spring AOP方面，InvocationHandler 的实现是 JdkDynamicAopProxy，它会在某种程度上调用TransactionInterceptor来处理@Transactional。
因此，入口点是查看TransactionInterceptor#invoke(MethodInvocation)，这些代码会在@Transactional方法周围执行。
英文:
The proxy codes are not generated. It is actually some static codes that implement InvocationHandler. See this for a hello world example for how does it work.
In term of Spring AOP , the implementation of InvocationHandler is JdkDynamicAopProxy which will somehow invokes TransactionInterceptor for @Transactional.
So the entry point is to look at TransactionInterceptor#invoke(MethodInvocation) which are the codes execute around a @Transactional method.
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