Indroduction to Web Application

Indroduction to Web Application

• 1.
  Introduction To WebApplication 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!