Chapter 11: Web Pages and Scripting Alternatives

1. Web 101 Third Edition by Wendy G. Lehnert & Richard L. Kopec Chapter 11:Web Pages and Scripting Alternatives

2. Learning Objectives • Learn what CGI means • Find out what Java applets can do and how to add them to your Web pages. • Learn how data-driven Java applets make it easier to manage frequent Web page updates. • Learn about XML • Learn about AJAX and how it works • Learn about PHP

3. Taking Charge • It’s very easy to add dynamic elements to your Web pages. • Ready-made JavaScripts and Java applets are available on the web for you to add to your Web page. • A JavaScript is a bit of code written to enhance a Web page. • A Java Applet is a small Java program that is attached to a web page.

4. Taking Charge • A Script is a small computer program written in a scripting language. • Scripts can be customized for you at an interactive Web site established for this purpose. (http://www.htmlgear.lycos.com/) • You can also download an authoring tool that helps you to do the same thing. (http://www.htmlgoodies.com/) • You can visit a freeware site and cut and paste one into your Web page.

5. Taking Charge • Some Javascript freeware sites (from Chapter 10):http://www.wsabstract.com/ http://Javascript.internet.com/ http://www.JavaScriptsearch.com/

6. Taking Charge • A scripting language is usually more limited and simpler than a full-fledged programming language. • Javascript interpreters are built-in to your Web browser, so no additional server support is needed to use it. • In addition to Javascript, your Web server might also support PHP or Perl. • PHP is a more standardized and potentially easier to use scripting language than Javascript. • Perl is another common scripting language. • There are also applets, small programs written in Java that can also be used on Web pages.

7. CGI Scripts • Some Web programs are intended to be done on the client computer, but others work best when done by the server. • In order to use server-side programs, the client must pass information to the server. • The protocol used by the client to pass needed information to the server is known as a Common Gateway interface (CGI). • The programs that process this information are known as CGI scripts. • Web page hit counters are commonly implemented this way:

8. CGI Scripts • A hit counter MUST be implemented on a server - Javascript cannot write to storage for security reasons - a rogue Javascript program could do a great deal of damage! • The hit count data collected by your computer is sent to a server for storage by the hit counter CGI Script whenever your Web page is accessed. • These CGI services are often housed on a 3rd-party computer, so three computers are involved: 1) one hosts the Web browser requesting the page, 2) one stores and serves the Web page, and 3) one offers the CGI service and data storage.

9. CGI Scripts • To install your own CGI scripts, you need access to a Web server that supports CGI. • Because of security concerns, such access is often very limited, if available at all. • CGI scripts are often written by programmers for programmers, but there are some that you can try. • Live Counter: http://www.chami.com/counter/classic/ • There are 5 files: 1. a “.class” file (a Java applet) 2. Three “.pl” files (a CGI Perl script) 3. A “.gif” file (images of the counter digits)

10. CGI Scripts • If your Web server supports CGI, you might consider trying LiveCounter. • Besides hit counters, CGI scipts can be used to • password protect your Web page • store data • add a site specific search engine to a web site

11. Java Applets • An applet is a small executable program written in Java attached to a Web page. • Applets require that a JVM be installed on the client computer. • A JVM (Java Virtual Machine) is a platform-specific browser add-on that makes it possible for Web browsers to execute Java applets.

12. Java Applets • Java is a full-fledged programming language. • Applets pose less of a risk than scripts do. • Applets can’t carry viruses since they can’t write to the local machine.

13. Java Applets • Programming Java Applets will require programming skill • You can find freely available applets online at applet sites • As an applet is software, so it will have a license too

14. Java Applets • To install an applet: • Download and unpack the applet • Read all available documentation • Insert the required HTML snippet into your Web page • Modify the PARAM values as needed • Upload your Web page to the server • Upload the required .class file • Upload any required support files

15. Data-Driven Web Pages • Data-driven Web page displays are used to minimize the amount of effort needed for ongoing Web page maintenance. • A Java applet reads and displays the information contained in a text data file. • Only that text file needs to be updated. • These applets are often highly customizable

16. Data-Driven Web Pages

17. Data-Driven Web Pages • Data-driven displays are not limited to text. • They can accept data from the user. • Applets that do this are freely available on the Web.

18. XML • Data-driven Web (DDW) sites do not work well with HTML because DDW pages are based on separation of content from presentation. • eXtensible Markup Language (XML) is a markup language designed to organize content (the data). • XML works cooperatively with CSS to present this content. • XML is often called a data description language.

19. XML • XML allows the user to define application-specific tags. • The user can use these tags to describe how the elements should be arranged relative to each other. • A CSS file can be created that describes how to display each of the user-defined elements. • An XML-enabled browser could then be used to display the Web page described.

20. XML • A sample XML content description: <!DOCTYPE news-list [ <!ELEMENT news-list (title, news*)> <!ELEMENT news (header, body, link?)> <!ELEMENT title ANY> <!ELEMENT header ANY> <!ELEMENT body ANY> <!ELEMENT link ANY> ]>

21. XML • A sample XML data file: <news-list> <title>Announcements</title> <news> <header>Assignment #4 Due Date Extension</header> <body>The deadline for assignment #4 has been extended to 6pm on Friday, April 5.</body> </news> <news>…</news> // another news element <news> <header>Course Project Assignments for 120</header> <body>These are the course projects for the 9:30 folks.</body> <link>http://www-unix.oit.umass.edu/~lehnert/ assignments.html</link> </news> <news>…</news> // another news element </news-list>

22. XML • An associated CSS file: title { font-size: 12pt; font-family: arial; color: red; font-weight: bold; text-align: center; margin-top: 10; margin-bottom: 10; display: block} header { font-size: 8pt; font-family: arial; font-weight: bold; margin-top: 10; margin-left: 6; display: block} body { font-size: 8pt; font-family: arial; margin-left: 6; display: block}

23. XML • The final Web page

24. XML • XHTML - eXtensible Hypertext Markup Language) • Combines HTML and XML. • Adds XMLs capability of creating new elements. • Most browsers recognize XHTML. • A transitional language as the Web pages are transformed from HTML to XML.

25. AJAX • Asychronous Javascript and XML. • Used to implement Web 2.0 applications (Chapter 4). • Formerly known as DHTML (dynamic HTML). • Allows browser to carry on additional tasks while it waits for some Javascript action to be completed. • Normally, browsers “freeze” until the Javascript task is completed. • Permits the creation of shared documents like those found in Google Spreadsheets and Docs. • Users can be entering data into a spreadsheet while the Javascript engine is busily dispatching it to the server for distribution to other document collaborators.

26. AJAX • Can also send form data to server as it’s entered, eliminating the need for a Submit button. • Used to power: • Microsoft Outlook Access • Google Maps • Yahoo! Maps • Flickr • Netflix • Google Docs

27. PHP • Newest kid on the scripting block. • PHP: Personal home page Hypertext Preprocessor • Open Source, server-side, scripting language • Intended to produce dynamic Web content. • Useful for frequently changing data displayed in stable format. • Simplifies task of accessing a database with frequently updated data, extracting desired information, and generating a Web page to display it.

28. PHP • Server used must support PHP. • How to tell?Insert this code into an HTML file:<?phpecho “Your server supports PHP”?> • If you see the string appearing in the echo statement above on the web page containing this code, then your server supports PHP.

29. PHP • PHP can be used to capture data from a Web page, process it, then generate a Web page to display the result. • Example, Punky’s Pizza Parlor • A “normal” Web page is created to capture order information:

30. PHP • The HTML file uses the ACTION attribute of the FORM element to trigger the PHP code:<form action=“order.php” method=“post”> • As you can probably guess, the PHP code to be executed when the SUBMIT button is pressed can be found in the file “order.php” • As you can also probably guess, the extension “.php” is used for files that contain PHP code.

31. PHP /* Start of PHP code */ $pizza = $_POST[‘pizza’]; /* get the pizza type from POST data */ $topping1 = $_POST[‘topping1’]; /* get 1st topping from POST data */ $topping2 = $_POST[‘topping2’]; /* get 2nd topping from POST data */ $topping3 = $_POST[‘topping3’]; /* get 3rd topping from POST data */ $quantity = $_POST[‘quantity’]; /* get quantity ordered from POST data */ /* create HTML page HEAD element */ echo “<html> <head> <title>Pizza Order</title> </head> ”; /* start the BODY element */ echo “<body> <h1>Punky’s Pizza Parlor</h1> <h2>Order Confirmation</h2>”; /* Report the order data */ echo “You ordered a ”. $pizza . “ pizza with ” . $topping1 . “, ”. $topping2 . “, and ” . $topping3 . “.<br>”; echo “Number ordered: ” . $quantity . “ <br><br>”; /* compute and report the cost */ printf(“Your cost, including 8%% tax: $%.2f<br>” , ($quantity*10)*1.08); /* write the date and time of order */ echo “Time ordered: ” .date(‘D, d M Y g:i:s A’) . “ <br>”; /* finish the page */ echo “Thank you for ordering from Punky’s Pizza Parlor!”; echo “</body></html>”; /* end of PHP code */

32. PHP • These assignment statements capture the data entered in the Web page form control elements (the selection lists). • As you can see, variables in PHP are preceded by a $ sign. • All PHP statements end with a semicolon. $pizza = $_POST[‘pizza’]; $topping1 = $_POST[‘topping1’]; $topping2 = $_POST[‘topping2’]; $topping3 = $_POST[‘topping3’]; $quantity = $_POST[‘quantity’];

33. PHP • These echo statements begin building the Web page dynamically, writing it to the browser piece by piece. • In PHP concatenation is indicated by a period (Javascript uses a +). • Strings are indicated the same way - using single or double quote characters as delimiters.echo “<html> <head> <title>Pizza Order</title> </head> ”; echo “<body> <h1>Punky’s Pizza Parlor</h1> <h2>Order Confirmation</h2>”; echo “You ordered a ”. $pizza . “ pizza with ” . $topping1 . “, ”. $topping2 . “, and ” . $topping3 . “.<br>”; echo “Number ordered: ” . $quantity . “ <br><br>”;

34. PHP • This statement performs the computation, then prints and formats the results so they look good. • The printf statement uses format specifiers: %% (to allow printing of a single %) and %.2f (indicating that a floating point value should be displayed to exactly 2 decimal places) printf(“Your cost, including 8%% tax: $%.2f<br>” , ($quantity*10)*1.08);

35. PHP • The echo statement uses the date function to print the current date according to its own specific format specifiers (see next slide). • The date format specifier used here isD, d M Y g:i:s A produces Sat, 09 Sep 2006 11:23:03 AM echo “Time ordered: ” .date(‘D, d M Y g:i:s A’) . “ <br>”;

36. PHP • The date function format specifiers

37. PHP • These two statements complete the Web page: echo “Thank you for ordering from Punky’s Pizza Parlor!”; echo “</body></html>”;

38. PHP • The Web page produced:

39. How Far Can You Go Without Programming? • Quite a ways! • You should be able to build functional and attractive Web pages. • Numerous scripts and applets are freely available on the Web to enhance your pages. • Many are easily incorporated into your Web page. • But some may simply not work!

40. How Far Can You Go Without Programming? • You can acquire an Integrated Development Environment (IDE) with a Rapid Development Application (RAD) editor which provides Graphical User Interface (GUI) to assist you. • You can also hire a programmer to (try rentacoder.com)! • Although programming is becoming easier and easier, some coding tasks can be quite challenging even for experienced programmers.