Document 7693539
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World Wide Web
and E-Commerce
Servers & Server Side Processing
Fall 2000
C.Watters
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Objectives
Understand the server’s role
Understand how processing is executed on
the server for dynamic web page content
CGI scripts
Active server pages
Database access
Servlets
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Client-Server Model
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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
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Server Side Processing
•
•
•
•
CGI – server applications
Server side scripts
servlets
JDBC/ODBC
• and databases
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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
Fall 2000
socket is an abstract
representation of a network endpoint.
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Dynamic Content
Browser
Server
Province ONT
NS
Get province from form
<html>
<html>
<h1>Catalog
<h1>Catalogfor
for NS</h1>
Ontario <h1>
<ul>
<ul>
<li>BlueRocks
<li>Niagara Falls
<li>Peggys Cove
<li>Bruce Trail
<li>Lunenburg
<li>Goderich
</ul>
</ul>
</html>
</html>
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Query database
Generate tags around the
query results
Send this text as body of
HTTP response
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CGI & scripts
CGI - Common Gateway Interface
allows data from forms to be used by
programs on the server
script is a program on the server
perl or C or C++ etc.
data returned to client as html document
may interact with a DBMS on server
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What does an HTTP response
look like?
Header
object file
Plain text about data
data
• Server response = Header + object file (generally)
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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>
Submit
Price:
• user enters data or selects options
• Data from form goes to server program called
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Form calling Simple CGI Example
<HTML><BODY>hi
Where to find the program?
<FORM action
="http://www.cs.dal.ca/~watters/cgibin/hello2.cgi” method =post>
<Input type = "submit">
</FORM>
</BODY>
</HTML>
Fall 2000
How to get data
to the server
Do it!
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Script for hello2.cgi
#!/opt/bin/perl
print
print
print
print
print
print
Print
print
Response doc type
"Content-type: text/html\n\n";
"<head>\n";
"<title>Hello</title>\n";
"</head>\n";
"<body>\n";
"<h1>Hello, Ottawa</h1>\n";
“<img src=“cancaphd.gif”>
"</body></html>\n";
HTML
doc
• try it
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Getting at Databases
ODBC - Open DataBase Connectivity
JDBC - java based
script programs can use these to make
database queries from server databases
Oracle, access, etc
results are sent back to client as html doc
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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";
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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!
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Example
Client puts tshirt in
shopping cart form on
web page
Cart.cgi is called
Makes purchase
(Tshirt)
Generates new page &form
Add a book
Cart.cgi is called
Makes purchase
( book)
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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 forth
keep everything in a database
Use Servlets
gets
tricky!!
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Servlets
java applications that are part of the server
always available (faster) than cgi scripts
provide continuity (state) for clients
written in java
can use JDBC to access databases
Used for: shopping, search, certificates,
agents, portals
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Other ways to process on Server
to generate dynamic data for web pages
Server side includes
Active server pages
Java server pages
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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
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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
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SSI example: ssitest.shtml
<html>
<h1>Getting the date from the server as I need it</h1>
<!--#echo var=“DATE_LOCAL” -->
<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>
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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!
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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>
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JSP (Java server pages)
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• <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() %>
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• </UL>
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<%@ 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>
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NOT the same as Active X
• Active X Components are “roughly” the
same as applets
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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
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