Drug Store Management free essay sample

In early days of the Web, a server could, dynamically constructs a page by creating a separate process to handle each client request. The process should open connection for one or more databases in order to obtain the necessary information. It communicates with Web Server via an interface known as Common Gateway Interface (CGI). CGI allowed the separate process to read data from HTTP request and write data to HTTP response. CGI suffered serious performance problems. Creating a separate process for each client request was expensive, in terms of processor and memory resources. It was also expensive to open and close database connection for each client request. In addition the CGI programs are not platform independent. Numerous CGI alternatives and enhancements, such as Fast CGI, mod_ Perl from Microsystems. While these solutions offer better performance and scalability, all of these technologies suffer from a common problem. They generate Web pages by embedding HTML directly in programming language code. Instead of embedding HTML in programming code, JSP lets you to embed specialized code (called scripting code) into HTML pages. JSP allows you to separate the markup language code; such as HTML from programming language code used to process user input, access databases, and perform other application tasks. One way of this separation take place through the use JSP standard and custom action elements in regular Web pages. Another way is to combine JSP with other Java Enterprise Technologies. For example Java servlets can handle input processing, Enterprise Java Beans (EJB) can take of the application logic, and JSP page can provide user interface. This separation means that with JSP, a typical business can divide its efforts among two camps that excels in their own areas of expertise, and comprise a JSP web development team with programmers who create the actions for the logic needed by the application, and page authors who craft the specifics of the interface and use the complex actions without having to do any programming. Another benefits are that a JSP page is always compiled before the server processes it. JSP page is compiled into executable code the first time it is requested, and invoking the resulting code directly in all subsequent requests. When coupled with a persistent Java virtual machine on a JSP-enabled web server this allows the server to handle JSP pages much faster. Java Server Pages is built on the top of the Java Servlets API, JSP has access to all of the powerful Enterprise Java APIs, including: JNDI (Java Naming an Directory Interface). Java is the default scripting language of JSP, but the JSP specification allows for other languages as well, such as JavaScript, Perl, and VBScript. Java acts as the front end, which drives its syntax from C and object-oriented features from C++. The main feature is platform independent. Java is popular among Internet programmers. It expends the universe of objects that can move about freely in cyberspace. Java can be used to create two types of programs, application and applets. An application is a program that runs on the computer, under the operation system of that computer. An applet is a tiny java program, dynamically downloaded across the network. 1. 1. 3 THE BYTE CODE The output of java compiler is not executable code it is byte code. It is a set of instructions to be executed by java run-time system called java virtual machine (JVM) it is an interpreter for byte code. Some of the java Buzzwords Simple Secure Portable Object-oriented Robust Multithreaded Architecture-neutral Interpreted High performance Distributed Dynamic SIMPLE It inherits the C syntax and many of the object oriented features of C++. It is the consolidated form of both. PORTABLE Programs to be dynamically downloaded to all various types of platforms connected to the Internet, some means of generating portable executable code is needed. SECURE With a help of java-compatible web browser, you can safely download java applets without fear. It is possible with the help of java execution environment and not allowing it access to other parts of computer. OBJECT-ORIENTED It organizes a program around its data and a set of well-defined interfaces to that data. Some of its concepts are as follows: Abstraction Encapsulation Inheritance. Polymorphism Exception Handling ABSTRACTION It’s the way of hiding the internal details but showing the external behavior. Example is car without the details of how it was made. ENCAPSULATION It is the mechanism that binds together code and the data it manipulates, and keeps both safe from outside interference and misuse. In java the basics of encapsulation is class, which is shared by the objects. Objects are sometimes called instances of a class. INHERITANCE Inheritance is the process by which one object acquires the properties of another object. It supports the concept of hierarchical classification for example golden retriever is part of classification dog, which in turn is part of mammal class, which is under the class animal without in each object would need to define its characteristics explicitly. POLYMORPHISM It is a concept that allows one interface to be used for general class of actions. Consider one example as stack. It is of three types one used for integer values one for floating values one for characters. The algorithms used are same in non-object oriented programming you would create three types of routines and with the help of polymorphism the general stack of routines is enough. EXCEPTION HANDLING Java provides very powerful exception handling mechanism. Exception handling minimizes the runtime loss. Java supports 100% Object Oriented exception handling mechanism in fact java itself is 100% OOPS. With the help of this feature various runtime errors are trapped and handled. ROBUST Java frees from having to worry about many of the programming errors. It checks the code at compile time and also at runtime. For example java eliminates the memory management problem by managing memory allocation and reallocation, exceptional condition such as division by zero can be resolved with the help of exception handling. MULTITHREADED Multitasking is a concept introduced in operating systems such as UNIX, Windows etc. , Multitasking is allowed only with 32 Bit Operating Systems. Multitasking supports concurrent execution of multiple tasks. The Operating System take care of the scheduling algorithms and switching logics. Now these powerful concepts in Operating Systems can be adopted in programming languages such as VB, JAVA etc. This technique is called as multithreading. Here program is divided into independent units called threads. Each thread can be executed concurrently. Java provides easy mechanism for multithreading. These are the programs that do many things simultaneously. ARCHITECTURAL-NEUTRAL Architectural Neutrality means Hardware independent. Cent percent Architectural Neutrality is not possible but we can develop tools to archive this with in very short period when compared with other languages. The main goal of it is that write once, run anywhere, any time. Java is designed for the distributed environment of the Internet, because it handles TCP/IP protocols. It is possible that two different computers to execute procedures remotely. Java revived these interfaces in package called Remote Method Invocation (RMI). Even the java libraries can also be distributed. EVENT HANDLING Event Driven programming model is a powerful one. We cannot predict the flow of execution before any user interaction. Systems Flow is completely controlled by the user’s action called events. Java provides event driven programming model, by its powerful libraries in AWT-Event and Swing – Event packages. Applets are event-driven programs. There are several types of events. The most common events are those generated by the mouse, the keyboard, and various control events are supported by java. awt. event package. 1. 1. 4 JDBC OVERVIEW: JDBC is a Java TM API for executing SQL statements. It consists of a set of classes and interfaces and interfaces written in the Java programming language that makes it easy to send SQL statements to virtually any relational database. JDBC extends what you can do in Java. With Java and the JDBC API, it is possible to publish a web page containing an applet that uses information obtained from a remote database. JDBC makes it possible to do three things: Establishes the connection to databases. Send SQL statements. Process the results. JDBC is a Low-level API and a base for Higher-level API. JDBC is a â€Å"low-level† interface, which means that it is used to invoke (or â€Å"call†) SQL commands directly. Because the JDBC API will tools and APIs, it also has to address the problem of conformance for anything built on it. 1. 1. 5 JAVA SOFT FRAMEWORK: Java Soft provides three JDBC product components as part of the Java Developer’s Kit (JDK): JDBC driver manager, JDBC driver test suite, JDBC – ODBC Bridge. The JDBC driver manager is the backbone of JDBC architecture. It actually is quite small and simple, its primary function is to connect Java applications to the correct JDBC driver and then get out of the way. The JDBC driver test suite tests that a JDBC driver implement all of the JDBC classes and methods and that it provides the entry-level SQL functionality for JDBC compliance. The JDBC – ODBC Bridge allows ODBC drivers to be used as JDBC drivers. It was implemented as a way to access some of the less popular DBMS’s if JDBC drivers are not implemented. Application The database server or back end is used to manage the database tables optimal among multiple clients to concurrently request the server for the same data. It enforces data integrity across all client applications and controls database access and other security requirements. SQL* Plus is a Structured Query Language supported by Oracle. Through SQL* Plus we can store, retrieve, edit, and run SQL commands and PL/SQL blocks. Using SQL* Plus we can perform calculations, list column definitions for any table and can also format Query results in the format Query results in the form of a report. SQL is a non-procedural language because it processes sets of records rather than just one data at a time and provides automatic navigation to the data. Here one can manipulate a set of rows rather than one at a time. SQL commands accept sets rows as input and return sets as outputs. The set property of SQL allows the results of one SQL statement to be used as input to another. Here one need not specify the access method of the data. SQL is utilized as the communication language with the database among the database users like databases administration, system administrations, security. Administrators, and application programmers. SQL provides commands for a variety of tasks including: Querying data. Inserting, updating and deleting rows in and object. Creating, replacing, altering and dropping objects. Controlling access to the databases and its objects. The SQL language is subdivided according to their functions as follows: Data Definition Language (DDL) (Or) Schema Definition Language Data Manipulation Language (DML) Data Control Language (DCL) SQL* Plus is a program or a tool available for working with an ORACLE database. It allows the user to: Create tables in a database Stores information in the tables Changes information in the tables Retrieve information in the form you choose Performing calculations on it and combining it in new ways. Maintain the database itself. 1. 1. 8 COMPONENTS OF WEB APPLICATIONS: The client side web pages themselves increasingly contain programming logic such as JavaScript or Visual Basic Script, as well as embedded software components such as Java applets and ActiveX Controls that can provide advanced functionality to users. These client-side elements of a web application are depicted I figure 1, box number 1.