为什么JMS会话对象不是线程安全的？

Question

为什么JMS规范的设计方式使得当创建Sessions的Connection对象是线程安全的（由线程共享）时，并发线程不能使用Session对象？

Answer 1

JMS 2.0 Spec

page 25

There are two reasons for restricting concurrent access to sessions.

First, sessions are the JMS entity that supports transactions. It is very difficult to implement transactions that are multi-threaded.

Second, sessions support asynchronous message consumption. It is important that JMS not require that client code used for asynchronous message consumption be capable of handling multiple, concurrent messages.

In addition, if a session has been set up with multiple, asynchronous consumers, it is important that the client is not forced to handle the case where these separate consumers are concurrently executing. These restrictions make JMS easier to use for typical clients. More sophisticated clients can get the concurrency they desire by using multiple sessions. In the classic API and the domain-specific APIs this means using multiple session objects. In the simplified API this means using multiple JMSContext objects.

Answer 2

JMS Session object is typically used for Transactions. And we all know transactions are thread specific and can't span across threads. Hence a transacted JMS session can't be used across threads. I believe for this reason JMS specification says session is not thread safe.