On-line Applications
Simple Applications
Any application which deploys web language and is target to run on internet can be categorized under web applications.A typical web application has the following requirements.
Application Requirements
Browser Accessibility:
Mostly most of the requirements come for a web application do come from browsers.It is since that web browser .it is since that the web services would normally be located at a different place from where the user is.We all know that the web site Hotmail.com,on which most of your email accounts,is at united states of america .Can you ever dream of going to US every time to check your mails??.The thing is that with internet,the location transparency is achieved .You need not actually know this fact that server is an US based.It is just enough if you know that web address you want is Hotmail.com And the browser is always there for you to something!!
But some applications rarely do use some special software,mostly custom built.Say,your chat application like yahoo chat or MSN chat!! Whatever be the case,the applications mostly use HTTP protocol .If security is required ,say for sites like amazon.com where the user may be required to enter their credit number ,secure socket layers are necessaries.
Ability to interact with the database:
Nobody would mind our application if it is just process some code and delivers the HTML output.Today most of the websites are in need of sorting various information about users in a secure way,for which database is the ultimate choice.Hence web language must necessarily posses this feature.
Wide adaptability:
The web language you should be supported by a wide variety of web servers.The web servers in turn ,should be supported by a wide variety of operating systems .It is since if you wish to put your coding on a different server,it should run by all means!
Easy Migration:
if your in need of transferring your application from a web server to similar web server located on a different computer ,it should not impose any new problems.The web language you use should not rely more on the server system which are using at present.
State Management:
HTTP is a stateless protocol,agreed! But there do arise some occasions like storing the information about the user until he leaves our site like storing the name of a user.Hence,your web language should provide this option.Remember the usage of session object in ASP and JSP,which are solely created for this purpose alone.
With all these points ,we must choose a web language that best satisfies all these above our requirements .Of course ,we have to analyse secondary factors like cost of web server,capability of web server programmer knowledge etc..,which are outside the scope of the book.
With all these points ,we must choose a web language that best satisfies all these above our requirements .Of course ,we have to analyse secondary factors like cost of web server,capability of web server programmer knowledge etc..,which are outside the scope of the book.
Design Tips:
If you have completely studied the book so far,you are familiar with at least the following web technologies like HTML,ASP,Perl,Servlet,Applet,JSP,VB script,Java script,style sheets.So here are some tips for you before you start building your/website:
*Never rely on a single technology.It may be better if you use Applet when you have to deal with Dynamic Graphics like building of charts ,Graphs etc..,but it is a foolish decision to construct a complete web site using Applets alone.The right mix of these technologies is the secret of success.
*Don't overload the server for everything.It is not good practice to check something like this on the server.Of course,there is no harm until the user types the username and gets the greeting.if he does not,then the web server is unnecessarily loaded besides increasing traffic on the network.A simple VB script or Java Script written on the client side would do the trick!!
*Use functions.It is good for debugging and encourages code reuse.
* Session objects do serve a noble cause.But it is not a wise thing to store unnecessary details on session objects like storing current date etc..,which carries less significance .The reason is that session and application variables are loaded every time when the page is accessed.
*Never let out important data client side scripting,like checking the password of a user versus his username.Since it is easy for anyone or breach this by clicking view source from the main menu and setting the HTML source,when the password also lies.
*Avoid using PLUGIN's .As the PLUGIN used in the server must cookies.As you are aware,cookies can be viewed ,modified and even deleted.
*Combine the commonly occurring code within multiple pages into a single file and use "include" directive to include that coding into the pages.Less modification effort alone is sufficient for any changes.
Sample On Line Exam Site:
Keeping these features in mind ,we have devise some simple application for you to use and have presented already ,you came across designing a guest book application in CGI and you came across designing a online exam site using ASP and JSP. The application has been developed using various web technologies like HTML foe front end,ASP as server side Technology with VB Script for implementation ,Back-end is MS-Access.Along with that ,design work is done using DHTML.
install the personal web server in the system information server on a windows NT/2 000 server machines.In most of the systems,IIS is automatically installed in your system.place the folder "Design" in the following path.Create a virtual directory named "design" and a map it to the design folder.Browse the web page as follows in the web browser.
On line Databases
This is a term which you have already come across many a times in this book .But this section address Online Databases in structured manner.
Functions of Online Databases
With an online databases you can display database data in an HTML tables ,a list,in bold text,in any front in any way in order.Order.Or even spread across several HTML pages or formatted differently depending on the database field value.You can replicate a relational database added by the script as the database grows .You can search and new pages automatically being added queries.You can add modify delete records online :you can gives visitors certain permission,while other permissions are restricted to the web master or administrator.you can let visitors enter their data into the database live,while you only moderate .You can use a database to look a certain area of your site,where by visitors register to get an automatic username and password .
You can maintain large amounts of structured data on a web site,easily searched,indexed,ordered and displayed in any way you desire
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