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Web and Java Establishments, Programming and Practice

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  1. Internet and JavaFoundations, Programming and Practice Rajkumar Buyya School of Computer Science and Software Engineering Monash University Melbourne, Australia Email: rajkumar@dgs.monash.edu.au URL: http://www.dgs.monash.edu.au/~rajkumar

  2. Agenda • Internet and its Evolution • Internet Tools • Web and its Programming • Java for Internet Programming • Java Nuts and Bolts • Java Platform • Developing Applets and Applications • Challenges and Future Directions

  3. What is the Internet ? • It is a global network of computers • that communicate with each other • using a variety of protocols and • overcoming various communication • barriers. • It is like International Telephone • System

  4. Internet Technology Evolution • Internet is much bigger than what we think • More than 25 years old • More than doubling every year • Technology effect • suddenly every body sees the need for a technology • like the radio or the TV • 10 terabytes flows everyday

  5. Internet • Use of internet advertisement/elections/newspapers • information is public • Ubiquitous technology • Network is the computer • Intranets - internal TCP/IP nets • PC accounts for 55% of total IT • Applications tied to platform - API lock-in

  6. Internet Evolution Internet everywhere Internet appliances Price based services Live communities ? ? ? ? ? ? ? On line connects to internet Secure payments Multi media Authoring Java VRML HTML File & mail TCP/IP Webpages Netscape 10% of Market 20% of Market Total Market

  7. Early Internet • Early Internet supported only email . • File Transfer Protocol development - ftp sites. • Network News was added to the Internet. • Archie - A program to canvass anonymous ftp sites and create a database of what is available • Gopher- A menu-driven interface used to search for information. • Archie and Gopher could answer questions only like ‘what FTP server contains info about “xxxx” ‘

  8. World Wide Web • World Wide Web conceptualized by Tim Berners-Lee at CERN in Switzerland • Concept of Hypertext led to the development of the Hypertext Markup Language (HTML) • Tim Berners-Lee proposed the ‘Browser’ program • Scientists at CERN designed a TCP/IP based protocol to share Hypertext information called HTTP. • WWW officially is described as a” Wide-area hypermedia information retrieval initiative aiming to give universal access to a large universe of documents.

  9. HTML • Hypertext -A little Hype and a Little Text. • Hypertext point to information which can be local or remotely located. • HTML -Derivative of the SGML( Standard Generalized Markup Language). • HTML -information , commands for the Browser for formatting documents. • HTML -The de-facto language for publishing on the Internet. • Hypermedia- Hyper-links to Multimedia.

  10. Internet Tools • Browsers- A tool used to view documents on the WWW • Web servers - Machines which run the HTTP-server Software that respond to HTTP requests which it receives • Authoring Tools - Editors specially made for editing HTML documents • Filters -Tools to convert legacy documents to HTML format • Scripting -Languages used for scripting • WAIS- Wide Area Information Servers (WAIS) for indexing and doing full text searches

  11. How does the Web work ? • Web -Designed around Client/Server Architecture • Web Clients ( Web Browsers ) -send requests for documents to any Web Server • Web Server -Program that responds to HTTP requests • Hyperlink • Web client connects to the specified Web Server • The server responds by sending the information asked for • The Browser formats the received HTML data and displays it

  12. How does the Web Work Send the “INFORMATION ABOUT C-DAC ACTS” HTTP The client sends an HTTP message to a computer running a Web Server program and asks for a document The information about C-DAC ACTS The web server sends the hypermedia HTML documents to the client. You end up seeing the document on your screen

  13. HTML document <HTML> <TITLE>Centre for Development of Advanced Computing </TITLE> <BODY BGCOLOR=“#E7CCCC” TEXT=“#000000” LINK=“#0000FF”> ... ... <A HREF=“mailto:webmaster@cdacb.ernet.in> webmaster</A> </BODY> </HTML>

  14. URLs • URLs- The Hypertext links we use today are known as Universal Resource Locator • URLs-Each name is unique across the Internet • An URL looks like this http://system.domain.ext:999/dir1/dir2/dir3/file.html?blue# • Parts of a URL are, Service type, System Name, Port, Directory path, Filename,Search Components or Variables • Service type, System Name, Directory path are the required parts of the URL

  15. CGI (Common Gateway Interface) • CGI makes the Web a Two-way interface • CGI -lets the user run a script when a web page is accessed • Information from the Web Client is received through simple ‘fill-in-the-forms’ kind of interface • FORMS - Integrates data sheets, menus , check boxes • CGI makes the Web interactive • CGI -complicated to setup ,requires PERL knowledge • HTML books talk less about CGI

  16. Authoring tools and Filters • Authoring tools- Editors for HTML documents • Editors similar to WYSIWYG word processing programs • Semi-WYSIWYG or completely WYSIWYG • Provide syntax checking and correction • Filters -Convert legacy documents to HTML format • Filters are useful when the documents already exist • Authoring tools- HoTMetaL, HTML Assistant -Shareware

  17. Preconfigured v/s Integrated Internet Products • Integrated Internet Products- From multiple vendors • Preconfigured Systems- Web Server and a Client ready to use • Sun’s Netra Internet Server • SGI’s WebFORCE Indy and WebFORCE Challenge S • Apple’s Internet Server Solution • DEC’s Internet AlphaServer • Integraph’s Web Server 10

  18. Future Directions • Additions to HTML (Grammar, Maths, Display control) • VRML (Virtual Reality Markup Language) • Security - Using Scrambling and Encryption • Common Client Interface (CCI)- Allows Clients to pass information back and forth between the Browser and the External Viewer • Charge Mechanisms • Performance Enhancements- Sending a page and graphics for that page in one connection

  19. Interesting URLs • http://www.whitehouse.gov ( The WhiteHouse) • http://www.w3.org (Everything about the WWW) • http://sunsite.unc.edu (Software on Sun) • http://www.indnet.org (India Net Foundation Services) • telnet://www.arbornet.org (Free Public Access Unix System) • http://www.infoseek.com (Search engines, Add URL) • http://www.infophil.com (World Alumni on the net) • http://www.rocketmail.com (Free Email ) • http://members.tripod.com (Free Website,2MB space) • http://www.bangaloreonline.com (Offers virtual web servvices for compinies to host their website). • http://www.prajavani.com (Kannada news paper on web)

  20. API Bottleneck MAC PC LAN LAN Server Network SUN

  21. Application Application The OS - Platform lock Applications tied to OS OS tied to Platform Application Application OS Application

  22. Application The Web * Seeded by HTML from CERN * Revolutionised by MOSAIC * Standardised, universal interface to data * Graphical Application Application BROWSER OS OS OS OS Application Application * Broadcast capability - publish once, reach millions

  23. Making life easier! • Data on the web • Browser platform independent • Click on application - run on any machine • Java the programming language of the 21 century

  24. Java and Java Computing

  25. Java - An Introduction • Java - The new programming language from Sun Microsystems • Java -Allows anyone to publish a web page with Java code in it • Java - CPU Independent language • Created for consumer electronics • Java - James , Arthur Van , and others • Java -The name that survived a patent search • Oak -The predecessor of Java • Java is “C++ -- ++ “

  26. Java From 10,000 Ft. • According to the world, Java is... • According to Sun, Java is... • On closer inspection, Java is

  27. According to the World, Java Is... • Snazzy Web pages • The cross-platform language we want • The rest-of-the-worlds answer to Bill • The C++ replacement we need • The C++ replacement we dont need • A bunch of hype

  28. According to Sun, Java is... • Simple and Powerful • Object Oriented • Portable • Architecture Neutral • Distributed • Multi-threaded • Robust, Secure/Safe • Interpreted • High Performance • Dynamic pogramming language/platform. Buzzword compliant!

  29. On Closer Inspection, Java is... • Simple • Pure • Portable • Surprisingly effective

  30. As a whole, Java is a Comprehensive Programming Solution • Object Oriented • Portable • High Performance • Geared for Distributed Environments • Secure

  31. Java as Object Oriented • “Objects all the way down” • Simple and Familiar: “C++ Lite” • No Pointers! • Garbage Collector • Dynamic Binding • Single Inheritance with “Interfaces”

  32. Java as Portable • Unlike other language compilers, Java complier generates code (byte codes) for Universal Machine. • Java Virtual Machine (JVM): Interprets bytecodes at runtime • Architecture Neutral • No Link Phase • Higher Level Portable Features: AWT, Unicode

  33. Total Platform Independence JAVA COMPILER (translator) JAVA BYTE CODE (same for all platforms) JAVA INTERPRETER (one for each different system) Windows 95 Macintosh Solaris Windows NT

  34. Java Write Once, Run Anywhere

  35. Architecture Neutral & Portable • Java Compiler -Java source code to bytecode • Bytecode - an intermediate form, closer to machine representation • A virtual machine on any target platform interprets the bytecode • Porting the java system to any new platform involves writing an interpreter that supports the Java Virtual Machine • The interpreter will figure out what the equivalent machine dependent code to run

  36. Java as High Performance • JVM uses “lean and mean” bytecodes • Small binary class filtes • Just-in-time Compilers • Multithreading • Native Methods

  37. Java in the World of Distributed Computing • Class Loader • Lightweight Binary Class Files • Multithreading • Dynamic • Good communication constructs • Secure

  38. Java as Secure • Language designed as safe • Strict compiler • Dynamic Runtime Loading (Verifier) • Runtime Security Manager

  39. Objective Feature C++ Ada Java C Encapsulation Yes Yes Yes Yes Inheritance Yes Yes No Yes Multiple Inherit. Yes Yes No No Polymorphism Yes Yes Yes Yes Binding (Early/Late) Both Both Early Late Concurrency Poor Poor Difficult Yes Garbage Collection No Yes No Yes Genericity Yes No Yes No Class Libraries Yes Yes Limited Yes Object Oriented Languages -a Comparison

  40. Java better than C++ ? • No Typedefs, Defines, or Preprocessor • No Global Variables • No Goto statements • No Pointers • No Unsafe Structures • No Multiple Inheritance • No Operator Overloading • No Automatic Coercions • No Fragile Data Types ?

  41. Basic Data Types • Types boolean either true of false char 16 bit Unicode 1.1 byte 8-bit integer (signed) short 16-bit integer (signed) int 32-bit integer (signed) long 64-bit integer (singed) float 32-bit floating point (IEEE 754-1985) double 64-bit floating point (IEEE 754-1985) • String (class for manipulating strings) • Java uses Unicode to represent characters internally

  42. Java Integrates Power of Compiled Languages and Flexibility of Interpreted Languages

  43. Two Types of JavaApplications • Different ways to write/run a Java codes are: Application- A stand-alone program that can be invoked from command line . A program that has a “main” method Applet- A program embedded in a web page , to be run when the page is browsed . A program that contains no “main” method • Application -Java interpreter • Applets- Java enabled web browser (Linked to HTML via <APPLET> tag. in html file)

  44. Java Environment/ Life Cycle of Java Code Java Interpreter Just in Time Compiler Runtime Environment Compile-time Environment Class Loader Bytecode Verifier Java Class Libraries Java Source (.java) Java Bytecodes move locally or through network Java Virtual machine Java Compiler Runtime System Java Bytecode (.class ) Operating System Hardware

  45. Java Development Kit • javac - The Java Compiler • java - The Java Interpreter • jdb- The Java Debugger • appletviewer -Tool to run the applets • javap - to print the Java bytecodes • javaprof - Java profiler • javadoc - documentation generator • javah - creates C header files

  46. Hello Internet // hello.java: Hello Internet program class HelloInternet { public static void main(String args[]) { System.out.println(“Hello Internet”); } }

  47. Program Processing • Compilation # javac hello.java results in HelloInternet.class • Execution # java HelloInternet Hello Internet #

  48. Simple Java Applet // HelloWorld.java: A sample applet import java.applet.Applet; public class HelloWorld extends Applet { public void paint(Graphics g) { g.drawString(“Hello World !”,25,25); } }

  49. Calling an Applet <HTML> <TITLE> Hello Worls Applet </TITLE> <APPLET code=“HelloWorld.class” width=500 height=500> </APPLET> </HTML>