Server-side Scripting, Exams of System Programming

Download Server-side Scripting and more Exams System Programming in PDF only on Docsity! | Server-side Scripting Slides courtesy of Xenia Mountrouidou URLs and web servers  Usually when you type a URL in your browser:  Your computer looks up the server's IP address using DNS  Your browser connects to that IP address and requests the given file  The web server software (e.g. Apache) grabs that file from the server's local file system  The server sends back its contents to you 2 http://server/path/file What are they and what are their differences? Server-Side vs. Client-Side Scripting Languages By Lories Slockbower Scripting Language  A new style of programming language different from system programming languages  Designed as glue language or system integration language  A single statement can execute huge number of machine instructions  Are normally ‘typeless’  Build complex algorithms and data structures..  Can create dynamic web pages  Change based on user input Types of Scripting Languages  Server-side Scripting Language  Can use huge resources of the server  Complete all processing in the server and send plain pages to the client  Reduces client-side computation overhead  Client-side Scripting Language  Does not involve server processing  Complete application is downloaded to the client browser  Client browser executes it locally  Are normally used to add functionality to web pages e.g. different menu styles, graphic displays or dynamic advertisements Different Scripting Languages  CGI (Common Gateway Interface)  Server-side solution  Needs to launch separate instance of application for each web request  Allows direct interaction with users  ASP.NET  Server-side technology to create faster, reliable and dynamic web pages  Supports .NET framework languages (C#, VB.NET, JScript.NET)  Provides flexibility to designers and developers to work separately Different Scripting Languages  VBScript  Microsoft’s scripting language  Client side Scripting language  Very easy to learn  Includes the functionality of Visual Basic  JavaScript  Client-side Scripting language  Easy to use programming language  Enhance dynamics and interactive features of a web page  Allows to perform calculation, write interactive games, add special effects, customize graphic selections, create security passwords Conclusion  Scripting languages make the web development work  Easier  Faster  Best utilization of resources  It is the programmer’s choice which one will suite the best considering  Knowledge  Practice  Resource What can server scripts do?  Customize a web page and dynamically change its contents  Respond to queries from users or from HTML forms  Access database and send the information back to the browser Advantages of server-side scripting  User does not need to download plugins like Java or Flash  User can create one template for the entire website  The site can use a content management system which makes editing simpler.  Generally quicker to load than client-side scripting  User is able to include external files to save coding  Scripts are hidden from view so it’s more secure. Users only see the HTML output. Disadvantages of server-side scripting  The scripts can be used by attackers to access the server. They do this by changing the URL to something that takes advantage of a hole in security. System administrators must keep all server-side scripting updated and use an application firewall to prevent this.  Scripting software must be installed on the content management system tools in order to store the dynamic data. How does it work?  Usually, JavaScript code starts with the tag <script language="JavaScript"> and ends with the tag </script>.  Files are first sent to the user’s computer by the web server which executes the script and displays the document.  The client-side script may also include browser directions based on certain user functions such as clicking buttons.  Frequently, you can see the the source card by viewing the file that contains the script. Example of client-side scripting  Suppose a person completes a form but omits information. When they slick the submit button, an alert box appears telling them about the mistake.  This is JavaScript and is an example of Client Side Scripting because all the activity takes place inside the browser. Advantages of client-side scripting  Allows for more interactivity  Can perform actions quickly without going to the server  May be easier to use for those whose browsers don’t support scripts  Are available from many free resources Client Side vs. Server Side Web  Simply defined, client-side code executes on the end-user's computer, usually within a web browser.  Server-side code executes on the web server, usually within a web application environment, which in turn generates HTML to be viewed in a browser. PHP 30 What is PHP?  PHP stands for "PHP Hypertext Preprocessor"  Server-side scripting language  Used to make web pages dynamic:  provide different content depending on context  interface with other services: database, e-mail, etc.  authenticate users  process form information  PHP code can be embedded in XHTML code 31 Hello World! 34 <?php print "Hello, world!"; ?> PHP Hello world! output Viewing PHP output zilla Firefox File Edit View History Bookmarks Tools Help @-2{-@ eG ft i file:///C:/Dal=|&] IGl-|Google |S) Oz a Firefox File Edit View History Bookmarks Tools Help @->-@ © @ [GB http:/focah| =] B) (IG-[Google [&) Hello world! Done h- PHP syntax template 36  Contents of a .php file between <?php and ?> are executed as PHP code  All other contents are output as pure HTML  We can switch back and forth between HTML and PHP "modes" HTML content <?php PHP code ?> HTML content <?php PHP code ?> HTML content ... PHP C:\Users\SCRAT\Dropbox\Belk\UCY Teaching\EPL344