Java and Client Server Models

The Role of Client Servers on the Web

Client server models provide the essential mechanisms for working with the Internet. In fact, most of the World Wide Web is built according to this paradigm. In client server models the web browsers run by millions of users are the clients. On the other side of the equation, are the web hosting systems that run at host sites and provide access to processes and data requested by the client. In this case, these hosting systems are the server.

This definition is based on software programs, where the client is a program running on a remote machine that communicates with a server, a program running at a single site and providing responses to client requests, such as web pages or data.

Java is a programming language that has been developed specifically for the distributed environment of the Internet. It resembles C++ language, but is easier to use. C++ is a high level programming language that performs low level functions. In computing, low level functions are those that focus on individual components and the interaction between them as opposed to abstracted and systemic features (high level). Java, like C++, is a language that is multi paradigm and supports object oriented programming (OOP), procedural programming, and data abstraction.

Object oriented programming is increasingly being used in client server technology. It refers to a programming language model that is organized by objects rather than actions, data rather than logic. OOP identifies objects (sets of data) and defines their relationship to each other. These objects are then generalized into a class. Methods or sequences of logic are applied to classes of objects. Methods provide computational instructions and class object features provide the data that is acted upon. Users communicate with objects and objects with each other through specifically defined interfaces called messages.

Java can create applications that are distributed between clients and servers in a network. Java source code (signaled by .java extension) is compiled (source code transformed into object code) into bytecode (signaled by .class extension). A Java interpreter then executes this bytecode format. Java interpreters and runtime environment run on Java Virtual Machines (JVMs). The portability and usability that characterizes Java stems from the fact that JVMs exist for most operating systems, from UNIX, to Windows, to Mac OS.

Java is one of the most well suited languages for working on the World Wide Web and the client server model is the primary models for working on distributed networks, of which the World Wide Web is just one. There is natural affinity between the two and this article will discuss some major characteristics of Java and how it can be utilized in building client server systems.

Major Characteristics of Java

This section will list and discuss some of Java’s major characteristic to support later discussions on how Java is used in client server systems. Perhaps the first and most obvious characteristics are that, given its syntactical similarity to C and C++ languages, Java is simple, simpler, in fact, than the languages it emulates. Java is also a robust programming language, which means it creates software that will identify and correct errors and handle abnormal conditions intelligently.

Another major characteristic of Java is that it is object oriented programming, which was described above. OOP is characterized by three properties also present in Java programming: inheritance, encapsulation, and polymorphism. Inheritance is a major component in OOP which defines a general class and then specializes these classes by adding additional details in the already written class. Programmers only have to write the new features since the specialized class inherits all the features of the generalized class.

In OOP, encapsulation is the inclusion of all methods and data required for an object to function. Objects publish their interfaces and other objects communicate with these object interfaces to use them without having to understand how the encapsulated object performs its functions. It is the separation of interface and implementation. Polymorphism in OOP in general and Java specifically, is the ability to assign a different set of behaviors to an object in a subclass from the methods describe in the more general class. Therefore, subclasses can behave differently from the parent class without the parent class having to understand why or change itself.

Multi threading is also an important characteristic of Java that increases interactive responsiveness and real time performance. Threading is the way a program splits or forks itself into two or more tasks running simultaneously. This allows for thread based multi tasking. Multi threading creates the effect of multiple threads running in parallel on different machines simultaneously.

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