Java Web Application Tutorial for Beginners

Posted by Infocampus HR on January 26th, 2019

Java Web Application

The aim of this text is to produce basic details of various parts in Web Application and the way will we have a tendency to use Servlet and JSP to make our initial java web application.

1. Web Server and client
2. HTML and HTTP
3. Understanding URL
4. Why we want Servlet and JSP?
5. Initial web Application with Servlet and JSP
6. Web container
7. Web Application Directory Structure
8. Deployment Descriptor

Web Server and client

Web Server could be software that may method the client request and send the response back to the consumer. As an example, Apache is one in every of the foremost widely used web server. Web Server runs on some physical machine and listens to consumer request on a specific port.

A web client could be a software system that helps in an act with the server. a number of the foremost wide used internet clients area unit Firefox, Google Chrome, Safari etc. once we request one thing from the server (through URL), web client takes care of making an invitation and causation it to the server so parsing the server response and gift it to the user.

HTML and HTTP

Web Server and web client are 2 separate softwares, therefore there ought to be some common language for communication. HTML is that the common language between server and client and stands for the hypertext markup language.

Web server and consumer wants a standard communication protocol, HTTP (HyperText Transfer Protocol) is that the communication protocol between server and consumer. HTTP runs on high of TCP/IP communication protocol.

Some of the vital components of HTTP Request are:

• HTTP technique – action to be performed, sometimes GET, POST, PUT etc.
• URL – Page to access
• Form Parameters – almost like arguments during a java technique, as an example user, password details from login page.

Understanding URL

URL is the form of Universal Resource surveyor and it’s used to find the server and resource. Each resource on the net has its own distinctive address.

Why we want Servlet and JSP?

Web servers are sensible for static contents HTML pages however they don’t skills to come up with dynamic content or a way to save knowledge into databases, therefore we want another tool that we will use to come up with dynamic content. There are many programming languages for dynamic content like PHP, Python, and Ruby on Rails, Java Servlets and JSPs.

Java Servlet and JSP are unit server aspect technologies to increase the capability of internet servers by providing support for dynamic response and knowledge persistence.

First Web Application with Servlet and JSP

We will use “Eclipse IDE for Java EE Developers” for making our initial servlet application. Since servlet could be a server aspect technology, we are going to want online instrumentation that supports Servlet technology, therefore we are going to use Apache Tomcat server. It’s terribly simple to set up and that I am an effort that half to you.

For easy development, we will add put together tomcat with Eclipse, it helps in simple readying and running applications.

Web container

Tomcat could be a web container, once an invitation is formed from consumer to internet server, it passes the request to internet instrumentation and it’s internet instrumentation job to seek out the right resource to handle the request (servlet or JSP) so use the response from the resource to come up with the response and supply it to internet server. Then the internet server sends the response back to the consumer.

When web container gets the request and if it’s for servlet then container creates 2 Objects HTTPServletRequest and HTTPServletResponse. Then it finds the right servlet supported the URL and creates a thread for the request. Then it invokes the servlet service () technique and supported the HTTP technique service () technique invokes doGet () or doPost () strategies. Servlet strategies generate the dynamic page and write it to respond. Once servlet thread is complete, container converts the response to HTTP response and sends it back to the consumer.

Some of the vital work done by web container is:

• Communication Support – container provides a simple manner of communication between an internet server and therefore the servlets and JSPs. as a result of instrumentation, we have a tendency to don’t got to build a server socket to pay attention for any request from internet server, analyze the request and generate response. of these vital and complex tasks area unit done by container and everyone we want to focus is on our business logic for our applications.
• Multithreading Support – instrumentation creates the new thread for each request to the servlet and once it’s processed the thread dies. Therefore servlets don't seem to be initialized for every request and save time and memory.
• JSP Support – JSPs doesn’t seem like traditional java categories and internet container provides support for JSP. Each JSP within the application is compiled by instrumentation and reborn to Servlet Java/J2ee Classes Bangalore so instrumentation manages them like different servlets.
• Miscellaneous Task – internet instrumentation manages the resource pool, will memory optimizations, run garbage man, and provides security configurations, support for multiple applications, hot readying different other tasks behind the scene that creates our life easier.

Web Application Directory Structure

Java internet Applications area unit prepacked as internet Archive (WAR) and it's an outlined structure. You’ll be able to export on top of dynamic internet project as a WAR file and unfasten it to see the hierarchy.

Deployment Descriptor

The web.xml file is that the readying descriptor of the net application and contains the mapping for servlets (prior to three.0), welcome pages, security configurations, session timeout settings etc.

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