PROPOSED SYSTEM (CHAPTER 5)

CHAPTER  5

PROPOSED SYSTEM

5.1 DESCRIPTION OF LANGUAGES & TOOLS USED

The Airline reservation system is a Web-based on-line reservation system that is intended to provide information needed to reserve seat(s) on certain flights.

This project is based on the 3-tier architecture. It is a pure JAVA/HTML/JSP/ Servlet solution.

     

JAVA

JAVA is Object-oriented Language ( supports abstraction, Encapsulation , Inheritance , polymorphism), developed by five Sun Microsoft Engineers-viz James Gosling, Patrick Naughton, Chris Warth, Ed Frank and Mike Sheridan, spent 18 months developing the programming language, called “OAK”, later renamed “JAVA” in 1995.

 It is portable (write-once-run-anywhere), security (provide firewall between networked application and client computer), and platform independent. Java programs could be run on computers running Microsoft Windows, UNIX, Macintosh. It supports multithreading. It is widely used for developing Internet based applications. It doesn’t support multiple  inheritance.

Java features are grouped into three editions and each having a Software Development Kit (SDK):  (i) J2SE (Java 2 Standard Edition)-original edition of java, consists of application programming interfaces (APIs) needed to built a java application or applet. (ii) J2ME (Java 2 Micro Edition) contains APIs used to create applications for a small computing devices, including wireless java application.

It is a reduced version of Java APIs and Java Virtual Machine. (iii) J2EE (Java 2 Enterprise Edition), an embellished version of J2SE to accommodate n-tier architecture has APIs to build applications for multi-tier architecture.

JSPs (Java Server Pages)

JSP is a server side technology. It is used for creating dynamic pages and  for presentation (for creating forms fields).

Sun introduced JSPs which offers a way to write snippets of servlet code directly within a static HTML page similar to Active Server Pages (ASPs). Each block of servlet code (called scriptlet) is surrounded by a leading <% tag and a closing %> tag.

Java Server Pages allow the use of expression and directives. A JSP expression begins with <% =and ends with %>. Any java expression between the two tags is evaluated, the result is converted to a string, and the text is included directly in the page. A JSP directive begins with <%@ and ends with %>. A directive allows a JSP page to control certain aspects of its workhorse.

JAVA SERVLET

A servlet is a generic extension-a java class that can be loaded dynamically to expand the functionality of a server. It provides best possible platform for web application development. It is neutral both across operating system and web server.  Servlets are commonly used with web servers, where they can take the place of CGI script (Common Gateway Interface). Servlets are multithreaded by nature. A servlet runs inside a Java Virtual Machine (JVM) on the server, so it is save and portable both across operating systems and also across web servers. “Write Once, Serve Everywhere”. Servlets are used in MVC architecture as a controller.

Servlets operate solely within the domain of the server, unlike applets, they do not require support for java in the web browser. Servlets are all handled by separate threads with in the web server process. Servlet is based on Request and Response paradigm. Servlet API contains two packages one javax.servlet package and the other javax.servlet.http package. These are not part of java core packages.

JDBC

The JDBC ( Java Database Connectivity) API defines interfaces and classes for writing database applications in Java by making database connections. Using JDBC we can send SQL, PL/SQL statements to almost any relational database. JDBC is a Java API for executing SQL statements and supports basic SQL functionality. It provides RDBMS access by allowing us to embed SQL inside Java code. Because Java can run on a thin client, applets embedded in Web pages can contain downloadable JDBC code to enable remote database access.

Although JDBC was designed specifically to provide a Java interface to relational databases, we may find that we need to write Java code to access non-relational databases as well.

The JDBC Architecture is as follows:

JDBC Architecture

Java application calls the JDBC library. JDBC loads a driver which talks to the database. We can change database engines without changing database code.

JDBC Driver Types

JDBC drivers are divided into four types or levels. The different types of jdbc drivers are:

Type 1: JDBC-ODBC Bridge driver (Bridge)
Type 2: Native-API/partly Java driver (Native)
Type 3: All Java/Net-protocol driver (Middleware)
Type 4: All Java/Native-protocol driver (Pure)

 

Type 1 JDBC Driver

JDBC-ODBC Bridge driver

The Type 1 driver translates all JDBC calls into ODBC calls and sends them to the ODBC driver. ODBC is a generic API. The JDBC-ODBC Bridge driver is recommended only for experimental use or when no other alternative is available.

Type 2 JDBC Driver

Native-API/partly Java driver

The distinctive characteristic of type 2 jdbc drivers are that Type 2 drivers convert JDBC calls into database-specific calls i.e. this driver is specific to a particular database. Some distinctive characteristic of type 2 jdbc drivers are shown below. Example: Oracle will have oracle native api.

Type 3 JDBC Driver

All Java/Net-protocol driver

Type 3 database requests are passed through the network to the middle-tier server. The middle-tier then translates the request to the database. If the middle-tier server can in turn use Type1, Type 2 or Type 4 drivers.

Type 4 JDBC Driver

Native-protocol/all-Java driver

The Type 4 uses java networking libraries to communicate directly with the database server.

JDBC process can be divided into five routines: loading  the JDBC drivers, connecting to the DBMS, creating and executing a statement, processing data returned by the DBMS and terminating the connection with the DBMS.

JDBC/ODBC bridge driver can be loaded by calling the Class.forName( ) method and passing drivers name sun.jdbc.odbc.JdbcOdbcDriver. For example

Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);

Java Script

Java Script is a scripting programming language, designed to add interactivity to HTML pages. It is usually embedded directly into HTML pages.

JavaScript gives HTML designers a programming tool which can put dynamic text into HTML pages. It can react to events, can read and write HTML elements, can be used to validate data, to detect the visitor’s browser and create cookies.

JavaScript can be put into an HTML page as follow:

<html>

<body>

<script type = “text/javascript”>

document.write(“Hello Word!”);

</script>

</body>

</html>

HTML (HyperText Markup Language)

HTML, an acronym for HyperText Markup Language, is the predominant markup language for web pages.

It provides a means to describe the structure of text-based information in a document-­­­­­­by denoting certain text as links, headings, paragraphs, lists, etc.- and to supplement that text with interactive forms, embedded images, and other objects.

HTML is Written in the forms of “tags” , that are surrounded by angle brackets.HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code (such as JavaScript) that can affect the behavior of Web browsers and other HTML processors.

CSS (Cascading Style Sheets)

CSS is typically used to create presentational effects for semantic HTML. Style HTML, an acronym for HyperText Markup Language, is the predominant markup language for web pages.

Style sheets form an integral part of dynamic HTML as they can be accessed and changed on-the-fly by scripting languages. CSS offers much more flexibility in terms of presentation effects.

With CSS, a designer can create the content with the appropriate, semantic markup and then use CSS to alter the appearance of their markup.The benefit of semantic HTML is that presentation of the text will be consistently applied, so long as the proper markup is consistently applied. Moreover, it allows for easy change of presentation, by simply editing the style sheets as well as being able to transfer the text from one site to another.

HTML documents can be delivered by the same means as any other computer file; however, they are most often delivered either by HTTP from a Web server or by e-mail.

Style sheets are used for adding styles (e.g. Font, Colors, Background, Margin, Border, Spacing, etc.) to web documents. It provides standards and uniformity throughout  a web site and other dynamic attributes. HTML elements on web page are bound with style sheet. The advantages of style sheet includes ability to make global changes to all documents from a single location. <Style>………</Style> tags are used for style process. Between this tags HTML tags are specified.

CSS syntax is rather logical and easy to learn, there are 6 basic rules of style definition.

e.g.       H1, B{color: olive; background: yellow; font-family: arial, courier}

Database (MySQL 5)

MySQL (My Structured Query Language) is a open source Relational Database Management System. MySQL is very fast reliable and flexible Database Management  System. It provides a very high performance and it is multi threaded and multi user Relational Database management system. The program runs as a server providing multi-user access to a number of databases. MySQL 5.0 is in two different variants: the MySQL Community Server and Enterprise Server. They have a common code base and include the various features.

TOMCAT SERVER :

Apache Tomcat (or Jakarta Tomcat or simply Tomcat) is a servlet container developed by the Apache Software Foundation (ASF). Tomcat implements the Java Servlet and the JavaServer Pages (JSP) specifications from Sun Microsystems, and provides a "pure Java" HTTP web server environment for Java code to run. Tomcat is not the Apache web server (which is a C implementation of an HTTP web server); these two web servers are not bundled together. Apache Tomcat includes tools for configuration and management, but can also be configured by editing XML configuration files. Apache Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies. The Java Servlet and JavaServer Pages specifications are developed under the Java Community Process. Tomcat can be used as either a standalone product with its own internal Web server or together with other Web servers, including Apache, Netscape Enterprise Server, Microsoft Internet Information Server (IIS), and Microsoft Personal Web Server. Tomcat requires a Java Runtime Enterprise Environment that conforms to JRE 1.1 or later.