Is the JMS QueueSender thread safe?

I want to use a QueueSender in a multi-threaded environment.

Is QueueSender.send() thread safe?

Is Activemqconnectionfactory thread safe?

As far as I know from the Java side, the connection is thread safe (and rather expensive to create) but Session and messageProducer are not thread safe. Therefore it seems you should create a Session for each of your threads.

Are Java variables thread safe?

Using Final keywordFinal Variables are also thread-safe in java because once assigned some reference of an object It cannot point to reference of another object.

No, a MessageProducer/QueueSender is not thread safe.

Or more specifically: The Session is not thread safe. The JavaDoc for Session explicitly mentions this in its first sentence:

A Session object is a single-threaded context for producing and consuming messages.

And since a MessageProducer/QueueSender is bound to a Session you must not use it from more than one thread at the same time. In fact you must not use it from two different threads at different times either!