The handling of messages is controlled by the "Inflow Adapter" which allows for some control over the call flow, but doesn't regulate the rate of message processing.
Flow control might be achieved at the JMS level using activation properties. This isn't a feature that's available yet. Usually one wants to control rate of processing. Java (AFAIK) has no good way to calculate per-thread CPU usage, and MEM usage is done through a global heap.