Lecture 7: Server side programming

Server Side Web Programming
Web Information Systems 2015

Preliminaries
• HTML
– Standard mark up language to create web pages
• CSS
– Style sheets for web pages
• Javascript
– Client side programming
• Java, Perl, Python, Php

What are web servers
• Hardware or software
– Helps deliver the web content that can be
accessed through internet (Wikipedia)
Web Server
File System
Request
Response
Read Static
Files

knoesis.org
(Web Server)
http://knoesis.org/amit

Web Servers
• History
– CERN httpd
• Apache – 60%
– Open source
– Linux, Windows, Mac
• IIS -- Internet Information Service
– Microsoft
– Windows
• Mostly installed automatically
• Generally run on Windows Server edition
• High Performance
• Nginx
• Lighttpd
– Both usually used as forward and reverse Proxy

Apache Download
• Packages
– LAMP -- http://www.lamphowto.com/
– WAMP -- http://www.wampserver.com/en/
– MAMP -- http://sawmac.com/mamp/
• Apache Installation
– Ubuntu – sudo apt-get install apache2/Synaptic
Package manager
– Windows and Mac – Download Apache
• http://httpd.apache.org/download.cgi

Web servers
• Delivers static web pages
• Don’t we see a lot of dynamic pages on the
web?
– Weather reports
– Date time changes on web sites
– User information updates

Friends Likes
and Comments
Friends Updates
Facebook

Dynamic Web Pages
Web Server
Script
Request
Response
DB

Frontend
• Data has to be sent to the server and response
has to displayed.
• How do we send data to the server
– HTTP methods
– Javascript
• Ajax
• JSON, XML
– HTML Forms

HTTP Methods
• Get
– Data encoded in the URL
– For idempotent data
• No changes are done except on the users screen
• Basically for retrieving data
– http://knoesis.org
/<pagename>?<param1>=<value1>&<param2>=<value2>…
– Param and value is the data sent.
• Post
– Data goes with the message body
– Changes the state
• Adds or deletes data at the server
– Cannot backtrack the history because the URL will be the same

HTML Forms
• Pass Data to the server
– Text fields, check box, radio button, submit button
etc.
• For More
– http://www.w3.org/TR/html401/interact/forms.ht
ml

Example
<BODY>
<FORM action=”destination script/url”
method="post">
<INPUT type=“submit” value=" submit” >
</FORM>
</BODY>

Technologies at the Server Side

Technologies
• CGI
– Common Gateway interface
• Servlets – Need to know Java
• Php
– Hypertext Preprocessor

CGI
• Common Gateway Interface (CGI)
– Runs a scripts for every request – New process
• Drawbacks
– Limited Functionality
– Scalability Issues

Servlets
• Java Programming Class used to extend the
capabilities of server that host applications
accessed via a request-response programming
model.
• Java Technology’s answer to CGI.
• Advantages of Java?
• Needs a servlet container

Servlet Container
• Component of a web server that interacts
with the Servlets
– Manages the Lifecycle of a servlet
– Mapping URL to appropriate servlets
– Security, concurrency, deployment etc .
• Examples
– Apache Tomcat (opensource)
– Jboss (opensource)
– IBM Websphere

Tomcat Installation
• Follow
– http://tomcat.apache.org/tomcat-7.0-
doc/appdev/installation.html
• Eclipse + Tomcat
– http://www.coreservlets.com/Apache-Tomcat-
Tutorial/tomcat-7-with-eclipse.html

Plain HTML Text Servlet
package testPackage; // Always use packages.
import java.io.*;
import javax.servlet.*;
import javax.servlet.annotation.*;
import javax.servlet.http.*;
@WebServlet("/hello")
public class HelloWorld extends HttpServlet {
@Override
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("Hello World");
}
}

Interpreting the Servlet
• @WebServlet("/hello”)
– This is the URL relative to the app name
– http://knoesis.org:8080/hello
• doGet
– Code for an HTTP GET request. doPost also common.
• HttpServletRequest, HttpServletResponse
– Contains anything that comes from the browser
– Send data back to the browser
• @Override

Lets see how to generate a simple
HTML
<!DOCTYPE html>
<html lang="en">
<head>
..
</head>
<body>
...
</body>
</html>

Servlet that generates HTML
@WebServlet("/test1")
public class TestServlet extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println ("<!DOCTYPE html>n"
+"<html>n" +
"<head><title>A Test Servlet</title></head>n" +
"<body bgcolor="#fdf5e6">n" +
"<h1>Test</h1>n" +
"<p>Simple servlet for testing.</p>n" +
"</body></html>");
}
}

Modifying web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4”... >
<servlet>
<servlet-name>TestServlet</servlet-name>
<display-name>Print Text</display-name>
<servlet-class>testPackage.TestServlet</servlet-class>
<init-param>
<param-name> param1 </param-name>
<param-value> value1 </param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>TestServlet</servlet-name>
<url-pattern>/test2</url-pattern>
</servlet-mapping>
</web-app>
Passing
parameters
Custom URLs

Php
• General purpose server-side scripting
language originally designed for web
development to produce dynamic web pages
• Hypertext Preprocessor
• Dynamically Typed Language

Php – Hello World
• Embed PHP script into an HTML ﬁle
• Upload the ﬁle onto a Web server using
extension .php (Apache)
• Embed using the following delimiters
– < ? ... ? >
– <?php ... ?>
– <script language=”php”> ... </script>
– <% ... %>

Php – Hello World
<html>
<body>
<?php
echo "Hello World";
?>
</body>
</html>
Delimiters – seperates PHP
to non-PHP code
<?php ?>

Php Applications
• Wide range of applications (similar to CGI)
– Forms handling, etc.
• Wide range of PHP libraries
– Network connectivity (e.g. access FTP, IMAP, SMTP, etc
– Database connectivity (e.g. MySQL, dBase, Oracle,
etc.)
– XML/XSLT manipulation
– Image manipulation

GET – POST
• Access form ﬁelds through PHP array
– $HTTP_POST_VARS for POST method
– $HTTP_GET_VARS for GET method
– $_POST for POST method (>=PHP4.1.0)
– $_GET for GET method (>=PHP4.1.0)
$name = $_POST["name"];
$name = $_GET["name"];
• Similar to request.getParameter(“name”) in
doPost/doGet in Servlets.

Prints even numbers until
“max”
<html>
<head><title>A Test Php</title></head>
<body bgcolor="#fdf5e6">
<p> <ul>
<?php
$maximum = $_GET["max"];
for($i=0; $i<=$maximum ; $i=$i+2){
echo "<li>$i</li>";
}
?>
</ul>
</p>
</body>
</html>

References
• Common
– http://coronet.iicm.edu/lectures/mmis/material/s
lides_serverside_main.pdf
• Servlets
– http://courses.coreservlets.com/Course-
Materials/pdf/csajsp2/02-Servlet-Basics.pdf
• Php
– http://www.php.net/
– http://www.w3schools.com/php/

Friends Likes and
Comments
Friends Updates
Partial Changes

JSON, XML Handling
• Change the content type
• Construct a Json/XML
• Pass it as it is done for plain text or html
• More about this in the next class.
• Might be a part of the assignment

CGI/Perl
• 1987 – Before the web
• Text manipulation language
• CGI – Common Gateway interface
– Can run any language
– Commonly perl
• Advantages
– Mature language over a decade of history
– Free and most os support perl
– Vast network of perl developers
• Disadvantage
– Scalability
– Optimized for unix platform
– Different ways of doing the same thing hence not easy to learn

Lecture 7: Server side programming

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