fall 2000c.watters1 world wide web and e-commerce servers & server side processing

Fall 2000 C.Watters 1

World Wide Web and E-Commerce

Servers & Server Side Processing


Objectives

Understand the server’s roleUnderstand how processing is executed on

the server for dynamic web page content

CGI scriptsActive server pagesDatabase accessServlets


Client-Server Model


HTTP Connection

• 1. Client – makes an HTTP request for a web page– makes a TCP/IP connection

• 2. Server accepts request– Does any processing required – sends page as HTTP response

• 3. Client downloads page• 4. Server breaks the connection


Server Side Processing

• CGI – server applications

• Server side scripts

• servlets

• JDBC/ODBC • and databases


Servers• What does a server actually do

• 1.gets up and running in “listening mode”• creates a socket bound to its IP address & waits

• 2. Handles requests• detects attempt by client to connect

• creates a new socket for communication with client

• processes request– retrieve file

– run cgi script

• closes socket

socket is an abstract representation of a network endpoint.socket is an abstract representation of a network endpoint.


Dynamic Content

<html>

<h1>Catalog for NS</h1>

<ul>

<li>BlueRocks

<li>Peggys Cove

<li>Lunenburg

</ul>

</html>

Get province from form

Query database

Generate tags around the query results

Send this text as body of HTTP response

Province NS

Browser Server

ONT

<html>

<h1>Catalog for Ontario <h1>

<ul>

<li>Niagara Falls

<li>Bruce Trail

<li>Goderich

</ul>

</html>


CGI & scripts

CGI - Common Gateway Interfaceallows data from forms to be used by

programs on the serverscript is a program on the server

perl or C or C++ etc.

data returned to client as html documentmay interact with a DBMS on server


What does an HTTP response look like?

• Server response = Header + object file (generally)

Header object file Plain text about data data


Forms and Data• Forms are part of HTML document<form action=“http://www.dal.ca/doit.cgi” method = put >

Price: <input type=“text” name=“price”><input type=“submit”>

</form>

• user enters data or selects options• Data from form goes to server program called

SubmitPrice:


Form calling Simple CGI Example

<HTML><BODY>hi<FORM action ="http://www.cs.dal.ca/~watters/cgi- bin/hello2.cgi” method =post>

<Input type = "submit"></FORM>

</BODY></HTML>

Do it!

Where to find the program?

How to get data to the server


Script for hello2.cgi#!/opt/bin/perl

print "Content-type: text/html\n\n";print "<head>\n";print "<title>Hello</title>\n";print "</head>\n";print "<body>\n";print "<h1>Hello, Ottawa</h1>\n";Print “<img src=“cancaphd.gif”>print "</body></html>\n";

• try it

Response doc type

HTMLdoc

http://www.cs.dal.ca/~watters/cgi-bin/hello.html


Getting at Databases

ODBC - Open DataBase ConnectivityJDBC - java basedscript programs can use these to make

database queries from server databases Oracle, access, etc

results are sent back to client as html doc


Perl example to ORACLE

print "<head>\n";print "</head>\n";print "<body>\n";print "<h1>Calendar</h1>\n";print "<b>Course description enrol</b><br>";

&SetOracle;&RunSQL("Select * from Calendar");&StopOracle;

print "</body></html>\n";


BEING STATELESS!!

• Each http call is a new connection

• SO??– A new version of your script is run each time– No memory of previous events– pretty hard to implement a shopping cart when

it gets emptied everytime you contact the server!


Example

Client puts tshirt inshopping cart form on

web page Cart.cgi is called Makes purchase

(Tshirt)Generates new page &form

Add a bookCart.cgi is calledMakes purchase

( book)


Maintaining State in a Stateless Systems

Use your script to write data to a temporary file on the server and to start each time by reading any data in that file

use javascript to process activities in a given session and send results to server at end only

Hide data in forms and send it back and forthkeep everything in a databaseUse Servletsgets tricky!!


Servlets

java applications that are part of the server always available (faster) than cgi scriptsprovide continuity (state) for clientswritten in javacan use JDBC to access databases

Used for: shopping, search, certificates, agents, portals


Other ways to process on Serverto generate dynamic data for web pages

Server side includes

Active server pages

Java server pages


Server Side Include Files

• Server Side Includes (.shtml)

• Active Server Pages (.asp)

• Java Server Pages (.jsp)

These functions are performed before any data are sent to the browser


Server Side Includes (SSI)

• Shtml extension

• What happens:– Server gets request for a page (.shtml)– Server checks the page for SSI commands– Server executes those commands and inserts

new values into the page– Server sends the new page to the Browser

SSI example: ssitest.shtml

<html><h1>Getting the date from the server as I need it</h1>



<h2> I could do other things as well</h2><ul><li>a stock quote<li>an expected wait time<li>a price check<li>etc</ul> </html>


Server Pages

• Active Server Pages (microsoft) .asp

• Java Server Pages (Sun) .jsp

• Instructions for the server are included in the web page

• The server notices the extension and looks for those instructions and executes them!


Active server Page example:test1.asp<%@ LANGUAGE="VBSCRIPT" %>

<HTML>

<BODY>

Test1

<% If Time >= #12:00:00 AM# and Time <=#12:00:00 PM# then %>

<h3>Good Morning Ottawa</h3>

<% else %>

<H3>Hello Everyone</H3>

<% end If %>

</BODY>

</HTML>


JSP (Java server pages)


• <UL>• <LI><B>Expression.</B><BR>• Your hostname: <%= request.getRemoteHost() %>.• <LI><B>Scriptlet.</B><BR>• <% out.println("Attached GET data: " +• request.getQueryString()); %>• <LI><B>Declaration (plus expression).</B><BR>• <%! private int accessCount = 0; %>• Accesses to page since server reboot: <%= ++accessCount

%>• <LI><B>Directive (plus expression).</B><BR>• <%@ page import = "java.util.*" %>• Current date: <%= new Date() %>• </UL>


<%@ page import="hello.NameHandler" %>

<jsp:useBean id="mybean" scope="page" class="hello.NameHandler" /> <jsp:setProperty name="mybean" property="*" />

<html> <head><title>Hello, User</title></head> <body bgcolor="#ffffff" background="background.gif">

<%@ include file="dukebanner.html" %> <form method="get"> <input type="text" name="username" size="25"><br> <input type="submit" value="Submit"> <input type="reset" value="Reset"> </form> <% if ( request.getParameter("username") != null ) {%>

<%@ include file="response.jsp" %>

<% } %> </body> </html>


NOT the same as Active X

• Active X Components are “roughly” the same as applets


Recap

• Servers process browser requests• CGI can be used to run applications on the server from

web pages including accessing DBMS data• Servers are naturally stateless• Servlets (&other tricks)can be used to maintain state• Server side includes can be used to dynamically create

web page content before sending the page to the browser

• Agents are little independent pieces of software

fall 2000c.watters1 world wide web and e-commerce servers & server side processing

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