What is the difference between Java RMI and RPC?
RPC is C based, and as such it has structured programming semantics, on the other side, RMI is a Java based technology and it's object oriented.
With RPC you can just call remote functions exported into a server, in RMI you can have references to remote objects and invoke their methods, and also pass and return more remote object references that can be distributed among many JVM instances, so it's much more powerful.
RMI stands out when the need to develop something more complex than a pure client-server architecture arises. It's very easy to spread out objects over a network enabling all the clients to communicate without having to stablish individual connections explicitly.
The main difference between RPC and RMI is that RMI involves objects. Instead of calling procedures remotely by use of a proxy function, we instead use a proxy object.
There is greater transparency with RMI, namely due the exploitation of objects, references, inheritance, polymorphism, and exceptions as the technology is integrated into the language.
RMI is also more advanced than RPC, allowing for dynamic invocation, where interfaces can change at runtime, and object adaption, which provides an additional layer of abstraction.
1. Approach:
RMI uses an object-oriented paradigm where the user needs to know the object and the method of the object he needs to invoke.
RPC doesn't deal with objects. Rather, it calls specific subroutines that are already established.
2. Working:
With RPC, you get a procedure call that looks pretty much like a local call. RPC handles the complexities involved with passing the call from local to the remote computer.
RMI does the very same thing, but RMI passes a reference to the object and the method that is being called.
RMI = RPC + Object-orientation
3. Better one:
RMI is a better approach compared to RPC, especially with larger programs as it provides a cleaner code that is easier to identify if something goes wrong.
4. System Examples:
RPC Systems: SUN RPC, DCE RPC
RMI Systems: Java RMI, CORBA, Microsoft DCOM/COM+, SOAP(Simple Object Access Protocol)