J2EE Architecture

J2EE Chapters

Jee Introduction

Introduction to Web Technology

In the earlier days when Internet & Web was first started ,it was slow,vulnerable or problematic. Initially everything was just static pages. In those days, a web site had at most one page and it more often than not was called a home page.

The term “Internet application” or “web application” were introduced when dynamic content processing was started.Let us discuss in detail, now a days web application is a web site whose contents are generated dynamically before being sent to the browser.

First let’s understand how a web application works before learning Jee

When you browse the Internet, you basically request for a certain file located in a computer in the location you specify in the Uniform Resource Locator (URL). The computer where the file is stored is called the web server.Web server or container refers to standard runtime environment which is capable of providing specific services for deploying application components.

This web server main function is to serve anybody on the Internet who requests files it hosts. Because you never know when a user will visit and use your web application, your web server must be up and running all the time [24*7].

Request and Response exchange mechanism over internet happens using web browsers such as chrome, internet Explorer, Mozilla Etc

When you click or type in a desired URL i or in Address bar of your browser, the following things happen:

  • The client browser establishes a TCP/IP connection with the server
  • The browser sends a request to the server
  • The server sends a response to the client
  • The server closes the connection.

Note:

The Exchange of data from client and server happens with HTTP Protocol.

After sending the requested page to the browser, the server always closes the connection, whether or not the user requests other pages from the server.

What is Jee

What is Jee

 

JEE is a Java environment from Sun for developing, building and deploying Web-based applications which is platform Indepenedent.

JEE is open source or standard technology used for developing web Application.

JEE Stands for Java  Enterprise Edition.

It can used to developing multi-tier enterprise applications which includes standalone (desktop application) and Web Applications (client server application)

Note:

JEE is now renamed as JEE ( Java Enterprise Edition)

Combination of [ Servlet , JSP & JDBC Technologies ] collectively called as JEE Components

JEE Architecture

System Architecture

A well-designed software application is divided into separate logical parts called layers. Each layer has a different responsibility in the overall architecture.

Typical layers in a software Application are as follows:

  1. Presentation layer: In this layer are parts that handle the user interface and user interaction [such html & jsp pages ]
  2. Business logic layer: This layer contains components that handle the programming logic of the application [such as Servlets ]
  3. Data layer: This layer is used by the business logic layer to persist state permanently. This layer normally consists of one or more databases where data is stored.

For Better Understanding of system architecture

  1. Presentation layer can be called as User Interface or Client layer
  2. Business layer can be called as Server layer
  3. Data layer can be called Database layer

 

Implementing JEE

Developing Web Applications using JEE Technology

We have to adopt two main architectures when developing web applications in Java

First architecture – uses Servlets and JSP technology in the middle tier and can run on a simple web server or Application Server
Small and Medium application use this architecture.

 

Second architecture– uses Enterprise Java Beans (EJB) technology in the middle tier and can only run on Application Server
Large enterprise applications use this architecture

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