CMSC 433, Alan Sussman, U. Maryland (via
Bill Pugh) 1
CMSC433, Spring 2001
Programming Language
Technology and Paradigms
Java RMI
Alan Sussman
March 15, 2001
CMCS 433, Spring 2001 -Alan Sussman 2
Administrivia
•Read Chapter 15, pages 973-979, on RMI
•Exam
–answers posted on Exams web page
–Mean: 58 Median: 58
25%: 49 75%: 69
•Project 4 due April 4
–distributed chat server, using RMI
–posted today, central server running soon
CMCS 433, Spring 2001 -Alan Sussman 3
Last time
•Java libraries
–I/O using streams, Readers, Writers, filters
–java.util
•Vector, Dictionary, Enumeration, Bitset
•Collection classes (List, Map, Set, etc.)
•Multithreaded programming
–and the Java memory model
–Motto is: Be careful!
CMCS 433, Spring 2001 -Alan Sussman 4
Different Approaches to
Distributed Computation
•High-performance, parallel scientific apps
•Connecting via sockets
–custom protocols for each application
•RPC/DCOM/CORBA/RMI
–make what looks like a normal function call
–function is actually invoked on another machine
–Arguments are marshalled for transport
–return value is marshalled as well
CMCS 433, Spring 2001 -Alan Sussman 5
Remote Method Invocation
•Easy way to get distributed computation
•Have stub for remote object
–calls to stub get translated into network call
•Arguments and return values can be passed
over network
CMCS 433, Spring 2001 -Alan Sussman 6
Remote Objects and Interfaces
•Remote Objects are those that can be
referenced remotely
–extends java.rmi.UnicastRemoteObject
–constructor throws java.rmi.RemoteException
•Remote interfaces describe services that can
be provided remotely
–extends java.rmi.Remote interface
–all methods throw java.rmi.RemoteException
