There are many Web technologies, from simple to complex. To get started with development of web applications, Let us understand how exactly internet works.
When we browse any web page on Internet, we basically send a request to server from client as shown below ( server is a system where data is stored ).
We send a request from client in the form of URL (Uniform Resource Locator) to the Server.
Server processes the request & sends response back to client.
Request from client is sent to server using web browsers such as chrome, internet Explorer, Mozilla Etc
Example: When we type URL www.facebook.com in address tab of the browser. We are sending a request facebook server and server in turn sends the response for the request. Since the request to the server can come at any point of day, the server should be running 24*7 or throughout the day.
When you click or type in a desired URL in Address bar of your browser, the following things happen:
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.
J2ee is standard platform used for developing web Application.
It is a open source, platform independent technology used for developing web applications
JEE Stands for Java Enterprise Edition
Combination of [ Servlet , JSP & JDBC Technologies ] collectively called as JEE Components
It can used to developing multi-tier enterprise applications which includes standalone (desktop application) and Web Applications (client server application)
An organized or well designed software application consists of separate logical parts also called layers.
Each layer does have different responsibility in the overall architecture outcome.
Typical layers in a software Application are given below:
Presentation layer: This layer mainly contains user interface & user interaction components. Mainly consists of HTML & JSP page components.
Business logic layer: This layer contains components that handle the programming logic of the software application. This layer can also be called as controller layer.
Data layer:This layer mainly contain databases where data is stored & retrieved as per application needs
For Better Understanding of system architecture
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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