Chapter 1 Programming Languages for Web Applications

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Chapter 1

Programming Languages for Web Applications

Introduction

Web-related programming tasks include HTML page authoring, CGI programming, generating and parsing HTML/XHTML and XML (eXtensible Markup Language), creating dynamic HTML pages, writing HTTP clients and servers applications, Web site management, and Web applications. Programming languages used by Web programming professionals include HTML/XHTML, XML, Java, Java Server Page, JavaScript,

VBScript, Visual Basic, Active Server Page (ASP), C/C++, PHP, Perl, ASP.NET, VB.NET, and C#..

1.1 HTML (HyperText Markup Language) and XHTML

The HTML is a structure language with a formal definition for use in creating static Web pages or HTML documents that we request from Web servers around the world. A typical Web page may include the following information:

Text of its document with appropriate settings such as front, color, alignment, numbered and bulleted lists, etc; any hypertext links to other documents, images, and other media; tables and user feedback form

Embedded client-side scripts such as JScript

Embedded images and media

Embedded other objects such as Java Applet program, ActiveX, audio, video, and VRML objects

Embedded video, audio, and other formats via Plug Ins

XHTML 1.0 Standard

• HTML 4.01 was approved by W3C (World Wide Web Consortium http://www.w3.org/markup) in 1999

• XHTML 1.0 was approved by W3C in early 2000 for replacing HTML 4.01

• Just like HTML 4.01 but it was modified to conform to the XML standard

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• All XHTML tags are case sensitive

• DOCTYPE – document type

• xmlns – XML Name Spaces

Editing HTML/XHTML Documents Text editors:

• Microsoft’s Notepad, Wordpad, Word

• UNIX/LINUX’s vi, emac, pico

• Save the files with either an .html or .htm file-name extension

XHTML Document Structure

<?xml version = “1.0”?>

<!DOCTYPE html PUBLIC

“-//w3c//DTD XHTML 1.0 Strict//EN”

http://www.w3.org/TR/xhtml11/DTD/xhtml-strict.dtd>

<head>

</head>

<body>

<p> The First XHTML Page Welcomes You! </p>

</body>

</html>

1.2 DHTML (Dynamic HTML)

DHTML, Microsoft Dynamic HTML uses a number of technologies such as HTML, script, a Document Object Model, multimedia players/components, absolute page positioning, dynamic styles, data binding to a page, and so forth to give your Microsoft Internet Explorer browser the ability to interactive with all elements of a Web page and to allow it to manipulate

dynamic contents

dynamic styles

dynamic positioning

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1.3 eXtensible Markup Language (XML)

The XML is standard language from World Wide Web Consortium for putting structured document and data in a text file for use on the Web. It uses tags and attributes like

HTML, but XML allows users to define their own tags for delimit pieces of data, and leave the interpretation of data completely up to other applications. Features of XML include:

• Another file format for storing information in hierarchical formats

• XML documents can describe both themselves and their content

Meta-language that allows you to create and format your own document markups

XML specification: http://www.w3.org/XML

1.4 JavaScript

JavaScript is a scripting language developed by Netscape for used in delivering dynamic Web pages, and enabling client-side programming for interactivity. JScript is a Microsoft version of JavaScript. ECMAScript (European Computer Manufacturer's Association:

www.ecma.ch/stand/ecma-262.htm) ) is a standardized JavaScript/JScript. A dynamic Web page may contain JavaScript code, which is placed inside a <script> element and will be executed as the Web page is loaded into a Web browser. It may be used to monitor various user events and response to various user requests. Typical JavaScript applications may include

• Customizing Web pages

• Creating dynamic Web page

• Validating user form for CGI

• Manipulating cookies

• Interacting with frames

• Calling Java program

1.5 VBScript

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VBScript, a scaled down version of Microsoft' Visual Basic, allows active scripting to be added on Web client (IE 3.0 and up), and Web server scripting in Microsoft Internet Information Server (version 3.0 and up).

1.6 Perl

Perl (Practical Extraction Report Language) is a portable, interpreted language used primarily as a tool for writing scripts that perform such functions as:

Manipulate text in files

Manipulate files and processes

Extract data from files

Write reports

Perform networking tasks

Write CGI scripts to generate dynamic pages for form processing

Interface to databases

1.7 Microsoft Visual C++

Visual C++ include many MFC library classes for supporting Internet and Web programming:

CGI programming

Winsocket

WinInet is a higher-level API than Winsock supporting only HTTP, FTP and gopher client programs.

IIS's API or the MFC (Microsoft Foundation Classes) ISAPI server extensions classes

ODBC (Open Database Connectivity) for SQL Database access and DAO (Database Access Objects)

MFC support for ActiveX document servers

ActiveX controls

1.8 Java

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A general purpose programming language that can be used to create Applets that execute after the Web page is loaded. It is also used for writing server side applications.

Features of Java

Secure - virus-free, tamper-free Robust - not memory overwrite

Portable - run on different machine without change Java Components

The Java compiler - translate Java code to byte code

The Java interpreter - reading and executing Java byte code

The applet viewer Terms

Byte Code - A highly portable machine language for an imaginary Java computer

Java Virtual Machine (JVM) - a computer that runs Java byte code

Just-In-Time (JIT) compilation - some JVM can translate byte code into machine language

Java Programs

Java stand alone applications (console or window-based)

Java applets

Java applet

Small Java programs that run in a JVM and is incorporated into a Web Browser

An applet runs inside a Web browser or an applet viewer

An applet cannot manipulate the computer file system

An applet is launched from HTML page

Java class extends java.applet.Applet

Defined in the java.awt package

Java Applications

Network programming (java.net)

Applet for dynamic Hypertext Markup Language document (Java.Applet)

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Graphical User Interface

Stand-Alone Programs

Programs that runs on the computer in the same manner as any other window- based application