UMass Lowell Computer Science 91.460

Java and Distributed Computing

Prof. Karen Daniels

Fall, 2000

Lecture 3

HW#1 Jini Overview C++ Diagnostic Results

Mon. 9/11/00

new http://www.cs.uml.edu/~kdaniels/courses/java2000.html

Question from Last Lecture...



What is socket-based communication?

 In a Java context, Deitel answers this on p. 936 in introduction to Servlets. Java has networking support for:   “socket-based communications that enable applications to view networking as streams of data - a program can read from a socket or write to a socket as simply as reading or writing to a file.” “packet-based communications that enable individual packets of information to be transmitted - commonly used to transmit audio and video over the Internet.”  Chapter 21 of Deitel treats Java networking

Homework #1

Homework #1

Assigned Due Content

Wed, 9/6 Fri, 9/8 Fri, 9/8 Fri, 9/15 Read Ch 1 (Deitel) Mon, 9/11 Read Ch 1, 2 (Edwards) Read Ch 2, 3 (Deitel) Fri, 9/15 Assignment #1, Part 1 short-answer questions Mon, 9/18 Assignment #1, Part 2 “Hello World” programming (application and applet)

Homework is due at the start of lecture on the due date.

Introduction to Java Applications

   Java application is executed using the Java interpreter (but not inside browser like an applet) Application begins execution in main() main() is

static

method inside class Welcome1.java

// Save this in file Welcome1.java

public class Welcome1{ public static void main( String args[] ) { System.out.println( "Java is fun!" ); } }

javac

Welcome1.java Welcome1.class

java

Welcome1

Similar application code is on p.36 of Deitel, Chapter 2

HW#1 HelloWorld Application

 Refer to p. 36 of Deitel, Chapter 2 for their Welcome1.java application  Modify:  System.out.println( ) statement  Change name of class and file

Compiling and Running on a PC

Introduction to Java Applets

 Java applet is executed inside a WWW browser (or appletviewer) using a Java interpreter that is inside the browser.

// Save this file in Welcome1Applet.java

import java.applet.*; import java.awt.*; Welcome1Applet.java

javac

Welcome1Applet.java

public class Welcome1Applet extends Applet{ public void paint(Graphics g) { g.drawString( "Java is fun!”, 25, 50 ); } } Welcome1Applet.class

Welcome1Applet.html

Save this file in Welcome1Applet.html

appletviewer

Welcome1Applet.html

HW#1 HelloWorld Applet

  Refer to p. 86 and p. 90 of Deitel, Chapter 3 for their WelcomeApplet.java applet Modify:  .java file:    g.drawString( ) statement Change name of class and file Extend Applet instead of JApplet unless you want to use Swing here. If extending Applet, import java.applet.*;  .html file:  Change name of class and file

Compiling and Running on a PC

Appletviewer on a PC

Browser on a PC

Computing Environment

    Java 2 platform: Java 2 SDK v. 1.2.1

 http://www.javasoft.com/products/jdk/1.2

Jini v. 1.1

 http://www.javasoft.com/products/jini UML CS UNIX environment Optional:  PC environment (code must also run on UNIX)  Java integrated development environment  2 are on disk with Deitel textbook (NetBeans caveat)

Make sure you have a UML CS UNIX account

Jini Overview

What is Jini?

J

ini

I

s

N

ot

I

nitials

portions of this slide contributed by Ayal Spitz

Sun’s Jini Vision

  Initial Sun marketing focused on hardware   Appliances in a home or office connecting to a network Jini’s goal is to make it possible for all of these appliances to seamlessly detect and communicate with one another Technology can also support software services jCable box Video Tuner jTV Video Display jVCR Digital Storage jComputer portions of this slide contributed by Ayal Spitz jStereo

What is Jini?

 Java-based connection framework developed by Sun Microsystems  Philosophy:  plug ‘n play network   blur distinction between hardware and software “self-healing”  Elements: discovery, lookup, leasing, remote events, transactions, JavaSpaces

Background on Jini Technology

Lookup Service Service Item Proxy Attribute Attribute Attribute Attribute Client Service Item Proxy Attribute Attribute Attribute Attribute proxy manages service interaction Service Provider Service Item Proxy Attribute Attribute Attribute Attribute

5 Key Concepts

 Discovery: find communities on a network and join them  Lookup: use Lookup Service(s) to find services and use them  Leasing: resource is “loaned” to some consumer for fixed time period  Remote Events: allow services to notify others of their state changes  Transactions: protocol to support multiple services moving to “safe” state

Some Jini Definitions

    Service: an entity on the network (e.g. hardware device or software module) that can be used by other Jini participants Community: a group of Jini services that are “aware” of each other (typically workgroup size) Group: used by Jini APIs to specify and represent a community  But, due to network separation, different communities may have same group name Federation: a collection of communities that are “aware” of each other

Discovery Example: Multiple Community

Service Provider 3 Service 3 Item Service Provider 1 Service 1 Item Client A Service 1 Item Service 4 Item Lookup Service Service 2 Item Service 3 Item Lookup Service Service 1 Item Service 2 Item Service 3 Item Client C Service 3 Item Client D Service 1 Item Client E Lookup Service Service 4 Item Client B Service 2 Item Service 3 Item Service Provider 2 Service 2 Item Service 3 Item Service 4 Item Service Provider 4 Service 4 Item

Requirements for Service, Client

To be a Jini Service:  Either you or a delegate must be able to:     Connect to a TCP/IP network ( ) Participate in discovery to find a Lookup Service Register with a Lookup Service to provide proxy Keep leases current To be a Jini Client:  Participate in discovery to find a Lookup Service  Communicate with a Lookup Service to receive service proxy

Extra “machinery” needed:

- http server(s) for each machine to offer up downloadable code - RMI activation daemon

c:

Hello World in a Jini Setting...

HelloWorldServiceInterface.java

HelloWorldService.java

HelloWorldClient.java

corejini chapter5 client corejini chapter5 service corejini chapter5 HelloWorldServiceInterface.class

HelloWorldClient$Listener.class

HelloWorldClient.class

HelloWorldServiceInterface.class

HelloWorldServiceProxy.class

HelloWorldService$Listener.class

HelloWorldService.class

service-dl corejini chapter5 policy policy.all

HelloWorldServiceProxy.class

Who Else is in the Game?

(other providers of coordination frameworks/connection technologies/service architectures for distributed computing)    HAVi  Sony, Sharp, Toshiba, Philips, RCA, Matsushita, Hitachi, Grundig Microsoft & HP  ChaiAppliance Plug and Play  eSpeak  Universal Plug and Play  Network protocol level  XML device description Salutation Framework

Further Information – Jini

 Sun web sites 

http://www.javasoft.com/jini



http://www.jini.org

 Development – Books   “Core Jini” by W. Keith Edwards “The Jini Specification” by Arnold, O’Sullivan, Scheifler, Waldo, and Wollrath  Gartner Advisory:  Java Jini: A ‘Killer-App Enabler’ for Network Computing? http://gartner.jmu.edu/research/ras/83000/83044/83044.html

portions of this slide contributed by Ayal Spitz

C++ Diagnostic

C++ Diagnostic

 Assess C++ background  Will not contribute to the course grade  Answers on the way out of class  Name is optional  Provide code snippets, not entire programs  Leave unknowns blank

We’ll summarize results of the diagnostic in lecture.