"Bubbles" check your Private Messages for an important JavaRanch message.
Not sure what your question is, but the responsibility of the JMS Message Handler is to convert the JMS Message to a Spring Integration Message object type. While the two Message types are very similar in that they have a "body" in JMS it is called the "payload" in SI. And in SI we have a Header, where in JMS it is Properties. If you have a scenario where you are passing through SI, so receive a JMS message on one channel and send it out on another channel with JMS adapters you can configure it to just pass the whole JMS message as a payload in a Spring Integration channel which then takes that payload to the outbound channel to JMS. That would have no overhead as it is just a passthrough.
If you have a complicated JMS message with lots of Properties, it might take a few more milliseconds to convert those into SI Message header values.