anatomy & url

8/12/2019 Anatomy & Url

1/69

Anatomy of web

application and URL


2/69


3/69

A web application with one of the

busyiest networks

It handles transactionsfor more than 1 Lakh

customers a day


4/69

History of Web

Application


5/69

Two tier architecture


6/69

Example:

Designing a software that students can use to

find their current grade.

Here database of grades resides on the server,

and the application resides on the client (the

computer the student is physically interactingwith).


7/69

In this example of a 2-tier architecture. The two

tiers are:

1. Data server:

The database serves up data based on SQLqueries submitted by the application.

2. Client application:

The application on the client computer consumes

the data and presents it in a readable format to

the student.


8/69

Now, this architecture is fine, if you've got a

school with 50 students. But suppose the school

has 10,000 students. Here the problem arises.

Because every time a student queries the client

application, the data server has to serve up

large queries for the client application to

manipulate. This is an enormous drain onnetwork resources.


9/69

Solution to the above problem:

3-tier architecture:

By inserting another program at the server

level(server application).

Now the client application no longer directly

queries the database; it queries the serverapplication, which in turn queries the data

server.


10/69

Three tier arch itec tu re


11/69

Languages used in Two tier

architecture

Initially , web applications use webdocuments written in a standard format such

as HTML and more recently XHTML, which aresupported by a variety of web browsers.

Each individual web page was delivered to the

client as a static document, no operations couldbe performed on the web pages at the run time.


12/69

Continued

During the session, the web browser interprets

and displays the pages.

In 1995, Netscape introduced a client-sidescripting language called JavaScript, which

allowed programmers to add some dynamic

elements to the user interface that ran on the

client side.


13/69

Continued

This calls for a web site developmentenvironment with coding techniques capable ofaccepting a clients request and processingthese requests.

The result of the processing being passed backto the client via standard HTML pages.

The need to return standard HTML pages ,that

map to a users input , is due to the fact thatbrowsers use HTTP to communicate with a webserver and are designed to interpret and renderHTML on a clients machine.


14/69

MODERN TECHNIQUES


15/69

Some of the following led to the

modernization of web applications:

Three Tier architecture:

In this architecture ,the client (applicationsoftware at client side) is made to link with an

application program at the server (not the

database).

This application program at server side is thenconnected to the database.


16/69

Continued

The server in a three tier architecture

contains data of all the application

programs of the web application.


17/69

Continued

EG: J2EE :Java 2 Platform Enterprise

Edition

Aim : To provide developers a set of Application

Program Interfaces while reducing time,application complexity, and improving

application performance.

It defines a multitier architecture for developing

web products to answer the need from the

industry.


18/69

Continued

It provides different components(API) which

enables programmer to develop, deploy and run

java based web application.

Components : Application clients and applets

are components that run on the client (where

clients are web browsers in case of webapplications).


19/69

Continued

For example: Java Servlet ,Java Server Faces,Java Server Pages (JSP) technologycomponents are web components that run onthe server (here server is also a webapplication).

It works on the principle of Write Once DeployAnywhere (WODA).

A .Net application, Orkut can be deployed onlyon Windows therefore , it is

not a J2EE web application.


20/69


21/69

Types of Architectures


22/69

Model-view-Controller

(MVC Architcture):

It separates the web application in three layersnamely:presentation layer,logic layer and datalayer

It is considered a good practice as it modularizescode,promotes code reuse and allows multipleinterfaces to be applied

Also using this system we can generate differentviews of the same web pages

Eg:web pages for humans and web serviceinterfaces for remote applications


23/69

Push based vs Pull based MVC

Architecture

These frameworks use actions that do the requiredprocessing, and then "push" the data to the view layer torender the results. Struts, Django, Ruby onRails and Spring MVC are good examples of this

architecture An alternative to this is pull-based architecture,

sometimes also called "component-based". Theseframeworks start with the view layer, which can then"pull" results from multiple controllers as needed.

In this architecture, multiple controllers can be involvedwith a single view. Play, Struts2, Lift, Tapestry, JBossSeam, Wicket, Hibernate and Stripes are examples ofpull-based architectures.


24/69

Three tier architecture


25/69

Three-tier Architecture

In Three Tier Architecture, applications are structuredaround three physical tiers: client, application, anddatabase.

The Database is normally RDBMS

The Application contains the business logic, running on aserver and communicates with the client using HTTP

The client, on web applications is a web browser thatruns HTML generated by the application layer.

The term must not be confused with MVC. Unlike inthree-tier architecture, it is considered a good practice tokeep business logic away from the controller, the "middlelayer" in MVC


26/69

MVC ARCHITECTURE IN

DETAIL


27/69


28/69

Presentation Layer

The Presentation Tier or User Interface is the portion theuser sees when they open a web page in the browser

If you were to view the source code, you would only seecode such as HTML, Javascript, and Cascading Style

Sheets. On some sites, you may see Java Applets andFlash

Viewing source code on a web page, you would NOTsee database queries or loops or calls to classes or anybehind-the-scenes processing.

You may also setup the site design using Themes,Skins, and Cascading Style Sheets.

Languages used in this layer are typically HTML,DHTML, CSS and javascript.


29/69

Business Logic Layer

The Business Logic, Functional Process Logic, BusinessRules (all pertaining to the same thing), are kept in aseparate layer.

This is where you define your classes and source code.

This can be in the App_Code folder for your classes andmethods.

Web languages typically used in ASP.net are VB and C#JAVA SERVLETS. You would not use HTML orJavascript in this layer

In this layer you typically define your classes, functions,sub procedures, properties, etc.


30/69

Data Access Tier

The Data Access layer is where you define yourtyped datasets and tableadapters. It is whereyou define your queries or stored procedures

The business tier may then make use of thisfunctionality. In your classes, rather thandefining ad hoc queries, you may use a

TableAdapter to access the Data Access Layer(Dao Layer).


31/69

USER IDENTIFICATION

In web application development user

identification is a very important aspect.

It helps in making an intelligent server

program,that responds to clients request smartlyHTTP is a connection less protocol that is,every request

from client is treated as a new request,ie the network

cannot identify the user

To avoid user authentication again and again useridentification is implemented in web application itself.Eg

a program of click count seen on websites is the result

of this feature


32/69

Continued

It is mainly implemented using the following

techniques

URL REWRITING

HIDDEN FIELDS

CREATING SESSION OBJECTS

SENDING COOKIES TO CLIENT COMPUTER


33/69

Continued

URL REWRITING

You can append a token or identifier to the url

of the next resource

You can send parameter name/value pairsusing the following format

url?name1=value1&name2=value2

These values can be received by the server and thus

the server can identify the user by these valuespassed as tokens


34/69

Continued

HIDDEN FIELDSHidden fields can be passed from the static html

document

This can simply be done using form

ie

values are passed to the server depending on thenature of request ie get or post

for get request the url will be appendedwith(?a=10)


35/69

Continued

COOKIES

These are certain class files that server sends

to the client computerSo that it can identify the user by getting the

cookies when the next time the user requests

and reply intelligently

Eg:to be spoken


36/69

Continued

SESSION OBJECTS

This method creates the session object so that the

server can remember past requests

HttpSession class object is created and its timeoutis specified so that server can identify the user

within a given timeout

It is mainly used in authentication purposes

As in such a condition a server may remember thatgiven user is already logged in and thus to not to

treat its requests as new requests


37/69

CLIENT AND SERVER


38/69

CLIENT

A client can be a human, a computer, a

hardware device, a software that sends

requests and receives response from a

server.

In case of web applications a client is a

web browser.

For example: Internet Explorer, Firefox,Opera.


39/69

SERVER

A server is a computer program running to

serve the requests of other programs, the

"clients".

Thus, the "server" performs some

computational task on behalf of "clients".

The clients either run on the same

computer or connect through the network.

It is a software in case of web applications.


40/69

J2EE specific server

Container: It is a part of server where

J2EE components execute.J2EE content runs on containers and not

on Java Virtual Machine.


41/69

Continued

There are 2 types of servers:

Web Servers: Contain only web

containers. Servlets and JSP run on webcontainers.

Example: Tomcat (APACHE)


42/69

Application Servers: Contain both Web

containers and EJB (Enterprise Java

Bean) containers.

o EJB container provides services related to datatransformation.

o Example: Glassfish (Sun Microsystems ), Web

Logic (BEA), JBOSS.


43/69

How are requests and responses


44/69

How are requests and responses

haldled?

HTTP is a request/response protocol, which

means your computer sends a request for some

file (e.g. 'home.html'), and the web server sends

back a response ( followed by the file itself).

That request which your computer sends to the

web server contains all sorts of (potentially)

interesting information


45/69

This is passed as HttpRequest objects

These objects may be convertedaccording to language used at server side

Eg: This piece of information is converted

into HttpServletRequest/HttpServletResponse object in servlets.

Then using this ,we can access all the

information regarding request andresponse


46/69

The following HTTP request was received fromIP address 49.248.69.98 (port 18787) by IP

address 81.187.237.83 (port 80):

GET /dumprequest HTTP/1.1

Host: djce.org.uk

Connection: keep-alive

User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like

Gecko) Chrome/14.0.835.187 Safari/535.1

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Referer: http://www.google.co.in/search?gcx=c&ix=c2&sourceid=chrome&ie=UTF-

8&q=www.google.+om#pq=web+application&hl=en&cp=8&gs_id=19&xhr=t&q=http+r

equest&pf=p&sclient=psy-

ab&source=hp&pbx=1&oq=http+req&aq=0&aqi=g4&aql=&gs_sm=&gs_upl=&bav=on.

2,or.r_gc.r_pw.,cf.osb&fp=5d23229b5c1e7359&biw=1366&bih=662

Accept-Encoding: gzip,deflate,sdch

Accept-Language: en-US,en;q=0.8

Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3


47/69

INFORMATION CONTAINED IN HTTPREQUEST AND RESPONSE

Source IP address, port and proxy

Source IP address:

49.248.69.98

Source port:

18787

Via:not present

X-Forwarded-For:

not present


48/69


49/69

Requested URIRequested URI:/dumprequest

Together with the 'Host' header and the destination port

number(above), this specifies the document which should be

retrieved.

Given all these values we can determine that the URL of the

document which is being retrieved is: http://djce.org.uk/dumprequest


50/69

TYPES OF RESPONSES

http is a protocol that allows transfer of

only html pages.

Server programming languages are

converted to html pages and then

transferred through http.

S f


51/69

Server responses can be of two

types:

Static Response:

This type of response does not changewith time

Response of html and java script pages isan example of static response

NOTE: Static response must not be

confused with static pages.Java script is a dynamic page but its

response is static

C ti d


52/69

Continued

Dynamic Response:Dynamic response changes with time.

Response depends upon the request of

the client and also on the logic performedon the server by server side application.

Server side application programming can

be done through languages like Perl CGI,J2EE, .Net, etc.

NOTE: response of static pages can also

be dynamic

Uniform Resource


53/69

Uniform Resource

Locator


54/69

URL (Uniform Resource Locator)

In computing, a Uniform Resource Locator orUniversal Resource Locator (URL) is a characterstring that specifies where a known resource is

available on the Internet and the mechanism forretrieving it.

A URL is technically a type of Uniform Resource

Identifier (URI) but in many technical documentsand verbal discussions URL is often used as asynonym for URI.


55/69


56/69


57/69

URL Standard syntax

scheme://host.domain:port/path/filename

scheme - defines the type of Internet service. The mostcommon type is http

host - defines the domain host (the default host for http iswww)

domain - defines the Internet domain name, likew3schools.com


58/69

:port - defines the port number at the host(the default port number for http is 80)

path - defines a path at the server (Ifomitted, the document must be stored atthe root directory of the web site)

filename - defines the name of adocument/resource

Diff t t f h i l d


59/69

Different types of schemes include:

URL E di


60/69

URL Encoding

URLs can only be sent over the Internet using

the ASCII character-set.

Since URLs often contain characters outside the

ASCII set, the URL has to be converted into avalid ASCII format.

URL encoding replaces non ASCII characters

with a "%" followed by two hexadecimal digits.

URLs cannot contain spaces. URL encoding

normally replaces a space with a + sign.


61/69

Types of URLs

Absolute URL:

Dictionary meaning of word absolute is : not dependent

on any thing ie independent having its own existence,

same is the meaning of absolute urls.

An Absolute URL is, thus, something that is independentor free from any relationship from the rest. When you

use an absolute URL, you point directly to the file you

give exact location of the file.

eg :sitename.com/images/welcome.gifis anabsolute url as it specifies that an image file welcome.gif

located in the images directory, under your site name

domain.


62/69

Relative URLs :

A relative URL points to a file/directory in relation to

the present file/directory.

They have short urls as they are referring to root

directory/subdirectory.Relative urls helps webmaster

to maintain the site without rewriting the whole pathagain and again if they had made any changes in

directory.

eg : . . / image/welcome.gifis a relative url (The initial

two peroids (..) in the url instruct the server to move upone directory (which is the root directory), then enter

images directory and finally point at welcome.gif file )

URL and IP address


63/69

URL and IP address

IP address, or "internet protocol address", is a unique

identifying number given to every single computer onthe internet. Like a car license plate, an IP address is

a special serial number used for identification.

A URL, as stated before, is a name, designed forpeople to remember (IE yahoo.com). A DNS server is

used to convert that name to an IP address, which is

some odd number IE 209.191.93.52. After all, who on

earth who be able to remember websites as a seriesof numbers (that's why we, as "normal people", use

URLs instead of IP addresses).

For eg. 208.185.127.40=www.about.com

74.125.236.52=www.google.com.


64/69


65/69

Trivia point 3:it is possible to mask or digitally alter

the appearance of your computer's IP address. Youwould do this for the sake of privacy or to avoid

authorities tracking your online habits.

Trivia point 4:as of May 2008, the internet uses IP

addressing standard Version 4 (aka "IPv4"). There is a

new generation of addresses being designed called

IPv6. The biggest change is in the number of availableaddresses. Instead of 4.3 billion possible IP

addresses, IPv6 will bring us

34,000,000,000,000,000,000 billionpossible IP

addresses.


66/69

So, in short:

The URL/"Domain Name" is something for you toremember

The IP is for the computer to use to send the

message

The DNS is used to translate from the URL to IP

address. At present, the Internet uses Domain

Name System to convert a URL to an IP address.The DNS maintains a list of domain names and IP

addresses which are distributed throughout the

Internet in a hierarchical order.


67/69

DNS (Domain Name Server)

The Domain Name System(DNS) is a hierarchicaldistributed naming system for computers, services, or

any resource connected to the Internet or a private

network.

It associates various information with domain

names assigned to each of the participating entities.

Most importantly, it translates domain names meaningful

to humans into the numerical identifiers associated withnetworking equipment for the purpose of locating and

addressing these devices worldwide.


68/69

The Domain Name System makes it possible toassign domain names to groups of Internet resources

and users in a meaningful way, independent of eachentity's physical location. Because of this,World WideWeb (WWW) hyperlinks and Internet contact informationcan remain consistent and constant even if the currentInternet routing arrangements change or the participantuses a mobile device.

Internet domain names are easier to remember than IPaddresses such as 208.77.188.166 (IPv4)

or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). Users takeadvantage of this when they recite meaningful UniformResource Locators (URLs) and e-mail addresses withouthaving to know how the computer actually locates them.


69/69

anatomy & url

Documents