并发访问远程对象Java RMI

Question

I am currently studying how Java RMI works but I do not understand a certain aspect.
In a non-distributed multithredaded environment if methods on the same object are called simultaneously from different threads each of them will be executed on the respective thread's stack (accessing shared data is not a part of my question).
In a distributed system since a client process calls methods on the stub and the actual call is executed on the stack of the process that created the remote object how are simultaneous calls to a method handled? In other words what happens at the lets say server thread when there are two (or more) requests to execute the same method on that thread?
I thought of this question as I want to compare this to what I am used to - the executions being on different stacks.

Answer 1

how are simultaneous calls to a method handled?

It isn't specified. It is carefully stated in the RMI specification : "The RMI runtime makes no guarantees with respect to mapping remote object invocations to threads."

The occult meaning of this is that you can't assume the server is single-threaded.

In other words what happens at the lets say server thread when there are two (or more) requests to execute the same method on that thread?

There can't be two or more requests to execute the method on the same thread. The question doesn't make sense. You've posited a unique 'lets say server thread' that doesn't actually exist.

There can however be two or more requests to execute the method arising from two or more concurrent clients, or two or more concurrent threads in a single client, or both, and because of the wording of the RMI Specification you can't assume a single-threaded despatching model at the server.

In the Oracle/Sun implementation it is indeed multi-threaded, ditto the IBM implementation. I'm not aware of any RMI implementation that isn't multi-threaded, and any such implementation would be basically useless.