Java

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Java

• E-Commerce
• Prof. Sheizaf Rafaeli

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What is Java?

• A fundamentally new way of computing,
• based on the power of networks
• Write once -- run anywhere
• 450 million vs. 120 million?
• With Java technology, you can use the same
  application on any kind of machine -- a PC, a
  Macintosh computer, a network computer, a Ford
  car or a Krups coffee pot, or even new
  technologies like Internet screen phones.

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Java Hype

• Java could surpass Windows as the software
  platform with the world's largest base by the
  turn of the century.
• "All of you who have anything to do with software
  development ignore JAVA at your own peril"
• " JAVA - TODAY THE WEB, TOMMOROW THE WORLD!!"

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Thin clients

• Computers designed to be centrally-managed
• Configured with only essential equipment
• No CD-ROM, disk drives or expansion slots
• Therefore lower in cost, esp. Cost-Of-Ownership.

Net PC (Intel and Windows) NC (Oracle and
Sun) Web TV
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Client systems range from dumb terminals to
mostly autonomous PCs. Thin clients fall in
between. (Source Byte
Magazine)
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Why is Java important?

• With Java technology, the Internet and private
  networks become your computing environment.
• Remote computing, thin clients, distributed
  control and access
• Java animates the Web, makes it interactive,
  distributes content and power, and transforms the
  internet and information systems.

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How it works(in a web browser)
References to java software (applets) are
embedded in HTML
The Java virtual machine first does stringent
security checks, and then runs the applet, which
appears and interoperates inside the browser.
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Javas Secret the Virtual Machine (VM)
Virtual Machine a layer of software just above
the CPU that emulates a theoretical ("virtual")
chip's behavior. It hides--or Abstracts--the
machine-level stuff into a single layer of
software. The Java Virtual Machine, when
properly implemented, allows a Java application
to run on the CPU for which the VM is written,
regardless of the type of system on which the
Java programmers worked.
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How it works (2)(in a web browser)
The computer's operating system provides
machine-specific support for many of the actual
operations and interactions.
Result The user gets an interactive Java applet
running in a browser. The Java virtual machine
serves as consistent platform on different kinds
of computers and operating systems, so that the
same Java applet runs in browsers on PCs, Macs,
UNIX, PDAs, workstations, Network Computers, and
elsewhere.
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How it works (3)
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Javas Promises

• Simple
• like and unlike C, C
• Object Oriented
• Distributed
• Robust
• careful at handling data types
• no pointers
• Dynamic
• adaptable

• Secure
• Portable, small
• no implementation-dependent aspects
• High Performance
• could be better
• still hybrid compile/interpret
• Multithreaded

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Javas Perils

• A native OS might offer features that Java can't
  use without sacrificing cross-platform
  compatibility.
• Interpreted Java byte-code doesn't run as fast as
  complied native code.
• If a program must interact with legacy code or
  data, a more established tool or language might
  work better.
• A developer may have superior tools for another
  language or may be more productive using a
  familiar tool or language.
• A developer may not want to change, even if it
  costs money and customers.

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Java is not JavaScript

• Java is a full-fledged object-oriented
  programming language. Hybrid JIT compilation to
  byte code.
• can be used to create standalone applications
• Both client and server side, and used much in
  stand-alone embedded environments.
• Owned by Sun

• Interpreted, does not create applets or
  standalone applications
• Mostly client side, but some server software,
  (Netscape's SuiteSpot), lets developers write CGI
  programs in a server-side version of JavaScript.
• Owned by Netscape

A Java-enabled browser is not automatically a
JavaScript-enabled browser they require entirely
separate interpreters (licensed from separate
companies) Rather than competing with each other,
Java and JavaScript are a powerful combination.
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Applets
Applets vs. applications
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Anatomy of an Applet Reference
ltapplet codeFilename.class heightnumber
widthnumbercodebaseDirectory_containing_applet
alignsetting hspacenumber vspacenumbernamestr
inggt ltparam namename1 valuevalue1gtltparam
namename2 valuevalue2gtlt!-- Define alternate
content, for non-Java browsers --gtltH2gtImagine an
impressive Java applet herelt/H2gtlt/appletgt
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Example
ltapplet codeScrollingNeonMessage.class
height200 width400 codebaseappletsgtltparam
nameMessageText value"Bookmark this
page!"gtltparam nameScrollSpeed
value10gtltH2gtBookmark This Page!lt/H2gtlt/appletgt

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Java applet restrictions

• Not too fast!
• Byte code, not compiled
• No (or limited) access to files
• Applets have no memory-- they are stateless
  (however secure servers allow bypass)

• Limitations on number of sockets open
  (connections)
• How much of a closely held property of and by Sun
  Microsystems?

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Microsoft vs. Sun?

• Scott McNealy vs. Bill Gates?
• Sun thinks (hopes?) that Java will be an
  alternative to Windows
• Microsoft thinks otherwise
• Others now in the game

http//www.javasoft.com/lawsuit/index.html
Source Fortune Magazine
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Microsoft vs. Sun (2)
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How, where, by whom is Java used?

• Check out Suns report, at
• http//www.javasoft.com/nav/used/
• See JARS and GAMELAN
• C L experiment with office
• Wordperfect office suite?
• Net-It

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How, where, by whom is Java used? (2)

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Embedding an applet on your page

• You can find the applet.class files in your
  browser's on-disk cache and copy them
• To be used locally
• Or on your own server

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Embedding a remote applet on your page

• ltAPPLET CODEClock2.class
  Width170 Height150
  CODEBASEhttp//mis.huji.ac.i
  l/ttt/gt lt/APPLETgt
• Try the applet on
• http//mis.huji.ac.il/ttt/java.lecture.html
• and on http//www-personal.umich.edu/sheizaf/try
  java.html

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How to enable/disable JavaNetscape 3.0

• Go to "Options Network Preferences..." from the
  main menu
• Change to the "Languages" tab To enable make
  sure "Enable Java" check box is checked
• To disable make sure "Enable Java" check box is
  unchecked
• Restart the browser

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How to enable/disable JavaNetscape 4.x
(Communicator)

• Go to "Edit Preferences..." from the main menu
• Select "Advanced" panel To enable make sure
  "Enable Java" check box is checked.
• To disable make sure "Enable Java" check box is
  unchecked. Restart the browser

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How to enable/disable JavaExplorer

• Go to "View Options..." from the main menu
• Change to the "Security" tab
• To enable make sure "Enable Java programs" check
  box is checked
• To disable make sure "Enable Java programs"
  check box is unchecked
• Restart the browser

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How to enable/disable JavaExplorer 4.x and 5.x

• Go to "View Internet Options..." Change to the
  "Security" tab
• Select "Custom" and click on the "Settings..."
  button
• To enable make sure "Disable Java" is selected
  under "Java."To disable make sure a setting
  other than "Disable Java" is selected under
  "Java." If you're not sure which setting to
  choose, select "High safety"
• Restart the browser

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Sample IDE for Java online

• Try the online Java Web IDE at
• http//www.chami.com/webide/
• IBMs Visual Age for java
• Check out Symantecs Café, Visual Café Pro.
• Borland, Microsofts Visual J, Lotus
• Sybase PowerJ Metrowerks CodeWarrior
  Inprise Jbuilder Supercede for Java

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Java Security?

• Javas sandbox security model
• Active-X trust model
• In any case, safe network computing is an
  oxymoron
• Orange Juice works better

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The 10 Java Buzzwords

• Java Virtual Machine
• HotJava, Appletviewer, javac,. Servlets
• JDK, Java Development kit
• JAR, zip, Java Beans
• Sandbox vs. Trust security models

• AWT, Abstract Window Toolkit
• ByteCode
• JIT Compiling
• .class, .java (source and bytecode)
• JDBC, Java Database Connectivity ODBC in Java

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Java Glossary and cheatsheets

• http//www.mindprod.com/gloss.html
• http//www.freewarejava.com/
• http//metalab.unc.edu/javafaq/javatutorial.html
• http//www.javacoffeebreak.com/
• http//java.sun.com/docs/books/tutorial/
• http//www.mercury.com/java-tutor/session01/sessio
  n01.html

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The Java backlash

• It still does nothing (?)
• Does the world really need programmable toasters?
• How long does it take to develop, load, run?
• Will Microsoft succeed in busting the platform
  agnostic monopoly buster?
• Animation, interaction and dynamic content easier
  to achieve with DHTML
• Is it truly slow, secure, portable?

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Is Java taking root?

• In the browser
• On the server (servlets)
• As commercial applications
• In the arena of enterprise applications
• In teaching institutions
• For some bubble bursting and iconoclasm, see
• http//www.disordered.org

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A few more, and URLs

• Gamelan, JARS, Developer
• http//java.sun.com http//www.javaworld.com
• Best Java tutorial athttp//www.phrantic.com/sco
  op/onjava.html
• IBMs introduction to java, at
• http//www.ibm.com/java/education/intro/courseopti
  ons.htm/
• Java in five minuteshttp//www.zdnet.com/produc
  ts/garage/java/applet/
• Java in the future
• Windows, or OS/2 and hypercard?