webserver programming

http://wwwis.win.tue.nl/

/ department of mathematics and computer science/ architecture of information systems

technische universiteit eindhovenTU/e

webserver programming

ICT voor O&O

cursus 515

2,3,9 mar 2005


technische universiteit eindhovenTU/eday 1

• general introduction

• what is the web?

• what do we mean by webserver programming?

• when to use it?

• what does it look like?

• first introduction to Java servlets


technische universiteit eindhovenTU/ethe course is only a first introduction!

“you know Java”

“you know HTML”

we assume limited experience with them


technische universiteit eindhovenTU/ewe will not teach you:

• Frontpage, Dreamweaver, etc.

• website layout management (off-topic)

• website content management

• computer programming

• Java

• ASP, .NET, PHP, etc. (not used with Java)

• specific Java technology such as JINI, JAXL, JDBC, J… (too

advanced)


technische universiteit eindhovenTU/eweb technology

What is the web made of?

What does web interaction do?

What do we need server-side programming for?

What does a webserver do?

How does it fit into the webserver?


technische universiteit eindhovenTU/ewhat is the web made of?

consider a user interacting with a webpage

what technology does it take?



webpagesshown in

web client (browser)

webserver

documents

scripts

anotherwebserver

databaseetc.

what is the web made of?


technische universiteit eindhovenTU/ewhat is the web made of?

webserver

documents

scripts

anotherwebserver

database

web protocol

TCP/IP (Internet)protocols

low-level protocol

cables

webserver

TCP/IP (Internet)support

operating system

computerhardware

web browser

TCP/IP (Internet)support

operating system

computerhardware


technische universiteit eindhovenTU/ewhat does web interaction do?

webserver

documents

scripts

anotherwebserver

database

HTTP

TCP/IP (Internet)protocols

low-level protocol

cables

Apache

www.win.tue.nl

Unix

Sun SPARC

MS IE 6

this computer

Windows 2000

Intel-based PC

rp URL: http://www.win.tue.nl/ictoo/

GET /ictoo/

document + headers

rendereddocument


technische universiteit eindhovenTU/equiz time!

• what does http://www.win.tue.nl/ictoo/ mean?

• what happens when a user clicks on a link to it?

• what does http://

wwwis.win.tue.nl/~rpost/webprog/cgi/tictactoe.cgi?move=5

mean?

• why are URLs a good idea?



x What is the web made of?

x What does web interaction do?

What do we need server-side programming for?




technische universiteit eindhovenTU/ewhat is server-side programming for?

to create applications!

example:

http://wwwis.win.tue.nl/~rpost/webprog/cgi/tictactoe.cgi



example: tic-tac-toe (2)

We can play tic-tac-toe with HTML files.

Limitations?




We can play tic-tac-toe with HTML files.

Limitations:

• every response is fixed

• we can’t save the score on the server

• too many HTML files

• changing the layout is a tedious job

• changing the machine’s strategy is hard

• communication between players: ?




With a server-side program to generate the pages,

all limitations disappear:

• a response can depend on anything

• we can save the score on the server and show it

• no more duplication of HTML

• changing the layout is a one-time operation

• changing the machine’s strategy is easy

• users can play/chat/… via the application



conclusion: server-side programming supports

• generic layout

• generic functionality

(“generic”: for all webpages at once)



do people create tic-tac-toe games in HTML?

• yes, many websites are! e.g.

http://www.win.tue.nl/index.html

we will return to this example


technische universiteit eindhovenTU/eserver-side web applications vs …

client-side web applications

example: the Pacman applet by Benny Chow

• written in Java (source code is available)

• this is a Java applet (client-side web app),

not a Java servlet (server-side web app)

• (this course is about server-side web apps)


technische universiteit eindhovenTU/eserver-side web applications vs. …

client-side web applications: (e.g. Pacman):

• can have a much more powerful user interface

• require special web browser capabilities (plugins)

• must be written to run in user’s web browser

standalone (non-web) applications:

• even more powerful

• must be downloaded and installed on the user’s OS

• must be written to run on the user’s OS


technische universiteit eindhovenTU/eserver-side web applications

• limited interaction in user interface

• software + content + gathered data

reside on server

factors determining whether to use server-side web application:

security, availability, reliability, portability, maintainability,

manageability, UI flexibility, …





/ What do we need server-side programming for?





example: www.win.tue.nl (2)

• http://www.win.tue.nl/index.html

consists of HTML pages + images

• layout, images, buttons designed in

Photoshop

• first prototype made in FrontPage

• alternative with server-side programming:

http://www.win.tue.nl/




problems: maintaining consistency in look & feel

• (not all Photoshop layouts and images can be used on the web)

• not everybody uses FrontPage

• some parts of the site are already generated with

software; FrontPage doesn’t support that

• how to convert existing pages?

• virtually impossible to change the look and feel

while the site is up and running




answer: server-side programming

• the TU/e “webfilter”

• generates a common look & feel for arbitrary

webpages on the fly

• example: http://wwwstijl.tue.nl/filter43/http://wwwis.win.tue.nl/~rpost/webpro

g/cgi/tictactoe.cgi




“webfilter” vs. FrontPage

• solves all of the problems mentioned

• must be tuned (by a programmer) to work

on specific ranges of pages

• requires an uncommon way of authoring

• hard to sell

(users don’t trust it, techs don’t trust it)




more viable: a Content Management System (CMS)

• CMS = server-side web application for website

authoring and management

• solves most of the problems mentioned

• limits author to range of options supported by

CMS

• very popular

• example: www.win.tue.nl (uses the Typo3 CMS)


technische universiteit eindhovenTU/eready-to-use server-side programming

software packages you can freely install, configure, and use;

examples:

• CMS software

• wiki software

• blogging software

• database managers (e.g.

http://www.petriweb.org/phpMyAdmin

• much much more





x What do we need server-side programming for?





webpagesshown in

web client (browser)

webserver

documentsscripts

anotherwebserver

database etc.

Java servlets

where does server-side scripting fit in?


technische universiteit eindhovenTU/ewhat is a webserver made of?

• core functionality e.g. serving files from the filesystem

• built-in document generation e.g. error messages,

status messages

• getting a document from an executable (CGI)

• special webserver modules for scripting /

programming (SSI; PHP; Java servlets; ASP; etc)


technische universiteit eindhovenTU/eCGI: Common Gateway Interface

a standard way to call external programs from a

webserver

and let them return a document


technische universiteit eindhovenTU/eCGI: example

tic tac toe of course:

http://wwwis.win.tue.nl/~rpost/webprog/cgi/tictactoe.cgi

source code will be made available





x What do we need server-side programming for?

x What does a webserver do?

x How does it fit into the webserver?


technische universiteit eindhovenTU/eservlets

difference with CGI scripts:

scripting engine is integrated with webserver

• more efficient

• requires special webserver support

Documents

webserver programming