Serverside Technologies

1
Server-side Technologies

• Technologies that exist at the server side
• Where the real work occurs

2
Server-side Technologies

• Looking at .
• Client-side scripting v Server-side scripting
• Factors in selecting a technology
• Older and New technologies
• CGI, Fast CGI, Mod Perl, Active Server Pages
  (ASP), Cold Fusion
• Overview of Servlets
• Introduction to Java Server Pages (JSP)

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Client-side scripting v Server-side scripting

• Client-side scripting
• Validates user input
• Accesses the browser
• Enhances Web pages with ActiveX controls,
  applets, etc.
• Manipulates browser documents
• Client-side validation
• Reduces number of requests that need to be passed
  to server
• Client-side scripting limitations
• Browser dependency
• Viewable to users through View Source command
• JavaScript most popular client-side script

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Client-side scripting v Server-side scripting

• Server-side scripts
• Provides programmers greater flexibility
• Generates custom responses for clients
• Contains greater programmatic capabilities than
  client-side equivalents
• Has access to server-side software that extend
  server functionality

5
Server-side options

• Common Gateway Interface (CGI)
• Fast CGI
• Mod Perl
• Active Server Pages (ASP)
• Personal Home Pages (PHP)
• Cold Fusion
• Java Servlets
• Java Server Page (JSP)

6
Common Features

• All server-side frameworks share a common set of
  features
• Read data submitted by the user
• Generate HTML dynamically based on user input
• Determine information about the client browser
• Access database systems
• Exploit the HTTP protocol

7
Decision Points

• When evaluating which server-side technology to
  use, you need to consider a number of critical
  factors
• Ease of development
• How easily can you build new applications
• Performance
• How fast can the technology respond to queries
• Scalability
• Can the technology scale to thousands, even
  millions of users?
• Security
• Are there any inherent security vulnerabilities?

8
Common Gateway Interface (CGI)

• CGI represents one of the earliest, practical
  methods for generating web content
• Primarily written in the Perl programming
  language
• Unfortunately, some CGI programs suffer from
  scalability and performance problems
• Let us see why this happens

9
CGI Architecture

• Browser initiates request
• Web server receives request
• For each new request, web server spawns a new
  operating system process to execute the CGI/Perl
  program

Create new process
Web Server
Perl/CGI
Browser
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CGI Architecture

• For each browser request, the web server must
  spawn a new operating system process

CGI/Perl 1
Browser 1
Web Server
Browser 2
CGI/Perl 2
Browser N
Create new process
CGI/Perl N
11
CGI Architecture

• Spawning a new operating system process for each
  request takes time and memory
• Hence, CGI programs have inherent scalability and
  performance problems
• Almost all other server architectures address
  these problems

12
Fast CGI

• Developed by Open Market as an option for
  developing faster, more scalable CGI programs
• Works by creating a pool of processes for
  handling CGI requests
• When a server receives a CGI request, Fast CGI
  picks up one of the processes from the pool and
  assigns it to the task
• Without the overhead of creating new processes
  each time, Fast CGI is much quicker than
  traditional CGI

13
Mod Perl

• A module of the Apache Web server
• Embeds the Perl interpreter directly within the
  web server
• Perl programs are therefore precompiled
• Since Perl is embedded within the server, Mod
  Perl does not need to create a new process for
  each request
• Like Fast CGI, Mod Perl is much faster than
  traditional CGI

14
Server Extensions

• Several web servers provide extension APIs
  (Application Programming Interfaces)
• Netscape provides (NSAPI)
• Microsoft provides (ISAPA)
• Similar to Mod Perl, these programs run directly
  within the web server
• Hence, Server Extensions are much faster than
  traditional CGI
• Usually written in C/C, they are not portable
  across web servers
• E.g. if you develop using Netscape NSAPI, you
  cannot run it on Microsoft ISAPA

15
ASP (Active Server Pages)

• Developed by Microsoft
• Runs on Microsofts web server IIS (Internet
  Information Server)
• Developers add ASP code directly to their HTML
  pages
• When a client requests a page, the web server
  takes the HTML page, runs the ASP code within the
  page, and returns the result in another HTML page
• Faster than traditional CGI but only works with
  Microsofts IIS

16
Cold Fusion

• Developed by Allaire Corporation
• Provides excellent database access and tools
• Very good technology for Rapid Prototyping and
  Rapid development

17
PHP (Personal Home Pages)

• An open source project developed by volunteers
• Provides simple and powerful database access and
  tools
• Good for Rapid Application Development

18
Servlet

• Javas answer to the CGI script
• Do not confuse a servlet with an applet
• Applet a java program that runs within a browser
• Servlet a java program that runs within a web
  server
• Rapidly becoming most popular technology for
  developing web based applications

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Servlet Overview

• Servlets are a significant development in
  client/server computing for the web
• Java Servlet API standard extension to Java
• Provides a Java class that can be loaded
  dynamically to expand the functionality of a
  Java-enabled server
• Does not require Java support on the client side

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Servlet Overview

• Provides a generic mechanism for extending the
  functionality of any kind of server (not just web
  servers)
• e.g. could be used to extend the functionality of
  a Java-based ftp server, or a mail server to scan
  for viruses attached to email
• Makes it easier for applets to communicate with
  the server
• Created to solve one basic need recognised
  Generating dynamic web content

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History of Servlets

• In late 1996, the use of Java on the server side
  was developing
• Allows getting away from the use of sockets on
  the server side
• Software vendors were each developing their own
  approach
• Problem each technology was tied to a particular
  vendor server program

22
History of Servlets

• Better to have a generic technology so that
  server programs could have the write-once,
  run-anywhere approach
• Early 1997, JavaSoft (Sun Microsystems) released
  the Servlet API
• Designed to work on Java and non-Java based
  servers
• Most web servers support Servlets

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General mechanism

• Execute within the servers process space
• Each servlet handled by a separate thread within
  the server process, not as separate processes (as
  in CGI).
• Servlets are portable across different web
  servers and different operating systems
• Fast, powerful and portable replacements to CGI
  scripts

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General mechanism

• Persist between invocations (CGI scripts
  reloaded), resulting in significant performance
  benefits over CGI programs
• Servlets have full access to the Java APIs and
  also to third party component classes (e.g.
  database connections, etc.)

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Places where Servlets can be used

• Accessed by name to generate a HTML page
• Embedded inside a HTML page as a server side
  include
• These are useful when a web page is mostly static
  info but contains small sections of
  dynamically-generated info
• Embedded inside a HTML page using Java Server
  Pages (JSP) see these later

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3 types of servlet engine

• Standalone
• Server that contains built in support for
  Servlets (e.g. Tomcat)
• Does not exist for many web servers
• Disadvantage have to wait for a new server
  release to get latest servlet support
• Add-on
• A plug-in for an existing web server
• Many have been written for servers (e.g. Apache)
• Embedded
• Lightweight servlet platform that can be embedded
  in another application

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Advantages of Servlets

• Servlets have 6 main advantages
• Efficient
• Convenient
• Powerful
• Portable
• Secure
• Inexpensive
• Let us see why

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Advantages of Servlets

• Efficient
• For each browser request, the servlet spawns a
  light weight thread
• This is faster and more efficient than spawning a
  new operating system process
• Hence, servlets have better performance and
  scalability than traditional CGI

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Advantages of Servlets

• Convenient
• Servlets include built-in functionality for
• Reading HTML from data
• Handling cookies
• Tracking user sessions
• Setting HTTP headers
• Java is an object-oriented language which
  arguably can make development easier

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Advantages of Servlets

• Powerful
• Servlets can talk directly to web servers
• Multiple servlets can share data
• Particularly important for maintaining database
  connections
• Includes powerful techniques for tracking user
  sessions

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Advantages of Servlets

• Portable
• One of the advantages of Java is its portability
  across different operating systems
• Servlets have the same advantages (they are
  written in Java)
• Can be written on a Windows platform and run on a
  UNIX operating system
• Servlets can be run on any Java-enabled web
  server with no code changes

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Advantages of Servlets

• Secure
• Traditional CGI programs have a number of known
  security vulnerabilities
• Hence, a separate CGI/Perl script is usually
  required to provide the extra security required
• Java itself has a number of built-in security
  features
• Therefore, Servlets are regarded to be more
  secure than CGI programs

33
Advantages of Servlets

• Inexpensive
• You can download free servlet kits for
  development
• As many servlets that are required can be
  developed for free and run on many free
  Java-enabled web servers

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Servlets Example
import javax.servlet. import
javax.servlet.http. public class HelloWorld
extends HttpServlet public void
doGet(HttpServletRequest request,
HttpServletResponse response) throws
IOException, ServletException
response.setContentType("text/html")
PrintWriter out response.getWriter()
out.println("lthtmlgt") out.println("ltbodygt")
out.println("ltheadgt")
out.println("lttitlegtHello World!lt/titlegt")
out.println("lt/headgt") out.println("ltbodygt"
) out.println("lth1gtHello World!lt/h1gt")
out.println("lt/bodygt")
out.println("lt/htmlgt")
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Server Pages

• Microsoft IIS ASP (Active Server Pages)
• Sun followed suit JSP (JavaServer Pages)

36
Java Server Pages

• Related to Java servlets
• An extension of the Java servlet API
• Can be used alone or in conjunction with servlets
• Another method for developing server side
  applications
• We will look at these in more detail in next
  lecture

37
References

• Check out
• Fast CGI
• http//www.fastcgi.com
• Mod Perl
• http//perl.apache.org
• Active Server Pages (ASP)
• http//www.microsoft.com
• Cold Fusion
• http//www.allaire.com
• PHP
• http//www.php.net
• Servlet and Java Server Page (JSP)
• http//java.sun.com

38
Summary

• We have looked at
• Client-side scripting v Server-side scripting
• Factors in selecting a technology
• Older and New technologies
• CGI, Fast CGI, Mod Perl, Active Server Pages
  (ASP), Cold Fusion
• Overview of Servlets
• Introduction to Java Server Pages (JSP)