Introduction to Java and its Platforms

Apex T. G. India Pvt. Ltd

Introduction To Java

Birth

• December, 1990• 13 people to find next wave of computing• Convergence of media next big wave• Oak: a video on demand receiver toolkit• *7: failed video on demand appliance• WebRunner: failed Oak Mosiac clone

– First browser to run Applets

Early ChildhoodEarly Childhood

• April, 1995• Java: Front page news of San Jose Mercury• Netscape announces Java embedded browsers• Java released to the masses• 10,000 downloads in the first few months• 2,000 emails a day within weeks• Total bandwidth for Java site twice that of Sun’s

main site

Teenage Years

• Java growth stabilizes• IBM gives keynote speech

– Introduces term “e-business”– Names Java as standard “e-business”

platform• 90% of online transaction happen with

the help of Java within a year.• Java growth explodes again• Java tried on embedded devices again

Early Twenties

• 66 Java Technologies• 50 + Java Technologies in development• Open Architecture license

– Free usage– Intellectual property free

• Community Development process– No company control over Java

Java vs. JavaScript

• Java is NOT JavaScript• Java is:

– Programming language– Server sided – client never sees it– Cannot change the state of an HTML

page• JavaScript is:

– Scripting language– Client sided – server never touches it– Can change the state of an HTML page

What is Java?

• Programming Language• Platform independent

– Write for one operating system– Run on another

• Write once, run anywhere• Java Virtual Machine (JVM)

– Runs Java programs

How do they do that?

• Two step compile• First Compile

– Done by the programmer– Platform neutral

• Second Compile– Done by the JVM (Java Virtual Machine)– Platform specific– User doesn’t do anything special– Doesn’t affect original file

Java Advantages

• Cost• Architecture• Portability• Reusability

Advantage: Cost

• Buying programming software is expensive

• Java is free– Regardless of total number of users

• Free tools– Editors– Enterprise Servers

• Free tools + free language = more free tools

Advantage: Architecture

• Java distributed for free• Community board administered

– No company can “own” Java• Every day users can contribute:

– Idea– Code– Bug-fixes

• Your in control

Advantage: Portability

• Java is platform independent– Compiled programs run on any system

• Compiled files can be compressed• Compressed files known as Jar files• Jar files executable

– Without uncompressing

Advantage: Reusability

• Reusability is using past code in current problems– Not necessarily your code

• Some one has done your work• Use other’s work• Big time saver

Enterprise (J2EE) Technologies

• JDBC• Java Servlet• Java Server Pages (JSPs)• Frameworks(Struts,Hibernate,Spri

ng)• Enterprise JavaBeans (EJBs)• Java Messaging Server (JMS)

JDBC

• Data Access Interface• Access many data sources

– Database access– Spreadsheets– Flat Files

• Performs common task like– Connection pooling– Batch updates– Transaction management

Java Servlet

• Server Side programming• Extends current web server functionality• Server and Platform independent• Similar to CGI scripting• Access to all Java Technologies• Focused on content generation

– Programmers don’t have to worry about design

Java Server Pages (JSPs)

• Embedded in HTML pages• Creates dynamic content• Server Sided• Focused on content presentation

– Designers don’t worry about programming

• Looks like regular HTML of XML– Markup tag based

Frameworks

• Java provide some framework technology that follow MVC-design pattern for programming.

• It provides Independency , Reusability, Security to web application.

• Struts , Hibernate, Spring are the frameworks technologies of java.

Enterprise JavaBeans (EJBs)

• Focused on– Customizable– Reusable

• Interface with data sources– Databases– Existing Enterprise Information Systems

(Banner)• Write once, run anywhere

Enterprise Java Beans (EJBs)

• Distributed Client/Server Model• Code executed on server

– Closer to the data– More powerful machine then client

• Code localized to server– Changing server code doesn’t cause

change in client code

Java Messaging Service (JMS)

• Communication between components• Two styles of communication

– Point-to-point messaging• Like Email

– Publish/Subscribe• Like Email Lists

Java Messaging Service (JMS)

• Synchronous– Sent once, not guaranteed to reach

server– Lost if not received

• Asynchronous– Sent until it is acknowledged– Queued until message is retrieved

Example Enterprise Application

Insert DataSubmit Link

LinksDB

LinksServlet

Check data

Error PageErrorJSP

Formats Error

Insert

JDBCApp

Construct Insert

Error Message

Example Enterprise Application

Get Classes ClassesServlet

ClassesEJB

Get ClassesEIS

(Banner)

Get Classes

Return ClassesReturn Classes

Format List

Class ListJSP

No NoticesClass List

LibraryJMS

Check Notices

Who should use Java?

• People who:– Program Enterprise systems– Interact with environments out of their

control– Want maximum flexibility– Maintain large websites

Who shouldn’t use Java?

• People who:– Maintain small website– Don’t interact external sites or systems– Looking for a quick and dirty solution

Thanks

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