Java RMI

Summary

• Java History
• Java Distributed Object Model
• Bank Account Example
  • Reuse of Local Implementation
  • Reuse of Remote
• Java RMI at work
• RMI Implementation
  • RMI Implementation Transport

Java History

Invented by James Gosling at Sun

Originally called Oak

Originally used for PDAs then to set-top boxes, then to the internet

Java Distributed Object Model

• Remote Object
  • Accessible from different address spaces
• Remote Interface
  • Declarations for methods in a remote object
• Failure Semantics
  • Clients deal with RMI exceptions
• Similarities/differences to local objects
  • Object references can be params
  • Param only as value/result

Bank Account Example

• Server API:
  • Deposit
  • Withdraw
  • Balance

Reuse of Local Implementation

Interfaces are available everywhere, but specific instantiations (objects) may not be. It’s up to the implementer.

Reuse of Remote

More work on programmer in terms of extensions/implementations, but objects are immediately visible.

Java RMI at work

Server

BankAccount acct = new BankAcctImpl();
URL url = new URL("mywebaddress");
Java.rmi.Naming.bind(url, acct);

Client

BankAccount acct = Java.rmi.Naming.lookup(url);
float balance;
acct.deposit(5);
acct.withdraw(3);
balance = acct.balance();

RMI Implementation

RRL handles ser/des

• Similar to subcontract

RMI Implementation Transport

Endpoints contain transports which connect to other transports via channels.

• Endpoint
  • Protection Domain
    • JVM
  • Table of Remote Objects
• Connection Management
  • Setup, Teardown, Listen for connections
  • Liveness monitoring
  • Choice of transport
    • TCP/UDPA

IO on channel using connections

RRL decides which transport to use depending on location of client/server