Indroduction to Web Application
- 1. Introduction To Web Application Alex
- 2. Topic No programming detail Not for some specific programming language Focus on what it is Focus on how it works
- 3. Outline Client Server Communication HTTP Static Web Web Server Client Side Script Dynamic Web Application Server Beyond This
- 4. Client Server Communication Server listen Client send a request Server send a response back OSI Stack – Application Layer – Transport Layer – Network Layer – Data Link Layer – Physical Layer
- 5. HTTP Application Layer Protocol URL As Address Address Stack – HTTP: URL (domain + path) – TCP: ip + port – IP: ip – 802.11x: mac address – Hardware: broadcast
- 6. HTTP HTTP Request – Header (Key-Value Text) • Address (Host, Get or Post) • Describe Body • Describe Client • Other Stuff – Body • Post Parameters (key=value) • Files • Carry whatever you want
- 7. HTTP HTTP Response – Header (Text Key Value Pairs) • Response Status (2xx 3xx 4xx 5xx) • Describe Body • Other Stuff – Body • Browser case : HTML js css • Download case : anything you downloaded
- 8. Static Web Document Sharing Connection between Documents – Hyper Link Document is text and more than text Hyper Text = text + hyper link HTML = Hyper Text + style Hyper Text Markup Language
- 9. Web Server Manage static document files Give client what it ask for Apache Lighttpd Nginx etc How it works – Listen on a port (default 80) – Accept a http request – Locate the document client wants – Send that back to client as a http response
- 10. Client Side Script More than display and link – Animation – Response user action immediately – Some logic can run on client Browser can run – Javascript – Flash – Sliver light – VB Script, Java Applet, ActiveX, Extensions
- 11. Dynamic Web Think about a forum – User generate content – Topics changes all the time You can not do this static way – We need more then static files – We need to run a program when we accept a http request to generate response How?
- 12. Dynamic Web New Way – Listen to a port (default 80) – Accept a http request – Processing request • If static content, return that stupid file • If dynamic run a program return that result – Send result back as a http response
- 13. Application Server More then web server – An URL can map to a static file – An URL can map to a processing logic Ancient Way – CGI just run a executable program and return the standard output – Fast CGI : thread based
- 14. Application Server Now it works, functionally People finally got Web Application But it sucks – If we write an address which we should not write, Crash! – Print each line of html – Heavy work just for a forum
- 15. Application Server Most Web Applications do not need memory manipulate Output html in html way Solution – Interpret server side script in a html template when processing a request – Php is short for Php Home Page – Asp jsp rhtml
- 16. Application Server PHP
- 17. Application Server How it works – Listen to a port (default 80) – Accept a http request – Processing request • If static content, return that stupid file • If dynamic – Run the interpreter such as php interpreter – The interpreter interpret user program(php file) – Interpreter return the interpret result – Send result back as a http response
- 18. Application Server PHP style language limitation – Each interpreter instance for a request – No server global context – Low performance nature JAVA style (JAVA .NET) – Virtual machine execution (keep programmer from low level memory ops) – Compile instead interpret (greatly improve performance) – Web app and server all run in One VM
- 19. Application Server How it works (JAVA style) – JVM start a JAVA program (that's server) – Listen to a port (default 80)(run in VM) – Accept a http request (run in VM) – Processing request (run in VM) • If static content, return that stupid file • If dynamic – Parse the http request – Call the user define method which should process this request, – Send result back as a http response(run in VM)
- 20. Application Server JAVA program server should be – Tomcat (widely used) – Jetty (we use in current project) – Websphere (widely used in commercial) The user define method should be – doGet(request, response) – doPost(request, response)
- 21. Beyond This Web Service Web Socket High Performance Web High Availability Distribute Web
- 22. Q&A Thank!