Basicsofapplets 53-130303003217-phpapp02
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The document discusses the basics of Java applets. It defines applets as small Java programs used in internet computing that are transported over the internet, automatically installed on client machines, and run as part of a web document using a tool called appletviewer. Applets interact with users through AWT instead of console I/O and can be classified as local or remote. Key differences between applets and applications are that applets cannot access local files or run local programs and require an internet connection for remote applets, while applications can do these things and generally do not need an internet connection.
Basicsofapplets 53-130303003217-phpapp02
- 1. 1 Basics of Applet
- 2. 2 Objective On completion of this period, you will be able to learn • Basics of applet
- 3. 3 Recap In the previous classes, we have studied about • The various I/O streams and classes • How to write console based Java programs or applications
- 4. 4 Basics of Applets • Applets are small Java programs that are used in Internet computing • Applets • Transported over the Internet • Automatically installed in client machine • Run as part of a web document • Applets can be run using a tool ‘appletviewer’
- 5. 5 Basics of Applets contd.. • Applets interact with the user through the AWT, not through the console-based I/O classes • Clients download applets via Web browser • Browser runs applet in a Java Virtual Machine (JVM)
- 6. 6 Basics of Applets contd.. • Applets can be classified into two types • Local applets • Remote applets • Local applet • Developed and stored in local system • No need for internet connection for the local system • Local directories were searched to locate the specified applet
- 7. 7 Basics of Applets contd.. • Remote applet • Developed by someone else • Stored on a remote computer connected to the internet • Our system needs an internet connection • The applet is downloaded into our local system via internet • Run it on our system
- 8. 8 Loading of Remote Applet Internet Local Computer (Client) Remote Computer (Server) Remote Applet Fig. 53.1 Loading of remote applet Applet
- 9. 9 Web Browsers Requests Applet Client Computer Fig. 53.2 Request for applet 1. Browser shows web document 2. Web document contains an applet tag 3. Web browser identifies the tag 4. Client computer makes a request to web browser via internet 1, 2 Browser showing web document Web Server 3 4 4
- 10. Web Server Transmits Applet along with HTML 7 6 5 10 5. Web server locates the applet 6. Sends the applet code to the web browser 7. Through internet it is downloaded to client 8. Applet is executed 4 4 Fig. 53.3 Applet downloading 3 1, 2 Browser showing web document Client Computer 5 8 HTML, applets etc
- 11. 11 Some Points About Applets • Applets do not use main() method • They run in a browser • They cannot read or write the files from the local system • Applets cannot run any other program from the local computer
- 12. Some Points About Applets contd.. • Applets are restricted from using libraries from other languages such as C or C++ • They cannot communicate with other servers on the local network 12
- 13. 13 Discussion • What are the differences between applications and applets ? main() method Run stand-alone Possible Not possible Access local files Applications Applets Needed Not needed Can access Cannot access Run local programs Can run Cannot run Internet connection Needed for Remote applet GUI based Generally not needed GUI May or may not
- 14. 14 Summary • Java programs are two types • application • applet • Java applications are the console based programs • Applets are web enabled internet applications • Two types of applets • Local applets • Remote applets
- 15. 15 Quiz 1. Applets are console based applications 1. true 2. false
- 16. 16 Quiz contd.. 2. Internet browser runs Java applets 1. true 2. false
- 17. 17 3. Java applications are web enabled internet applications 1. true 2. false Quiz contd..
- 18. 18 Frequently Asked Questions • Explain about Java applets • List the differences between applets and applications