How Java Servlet Works?

Features of Java Servlet

There are 5 Features of Servlet are as Follow:

Portable: Servlet uses Java Programming language, and as we know java is portable language, so servlet is also portable.

Efficient: Servlets invocation is highly skilled as compared to any CGI programs.

Robust: JVM manages Servlet. That’s why Servlet is robust.

Performance: Servlet creates a thread for each request, so the performance of servlet is better than CGI.

Secure: Because it uses java language, so servlet is safe.

How Servlet Works?

Whenever a request comes, it received by the servlet, and then they forward the request to the web container. A Web container is responsible for handling the request by creating the new thread. Container creates multiple threads to execute various requests.

Let’s understand the working of Servlet –

1. The User sends a request by clicking a link for a servlet.

2. Then, the container finds the servlet and Create two instances.

  a.HttpServletRequest

  b.HttpServletResponse

3. After this, the container creates a thread for executing the request. So they call the servlet’s service() method and passes the instances as arguments.

4.Based on the HTTPRequest method sent by client, service( ) method decides which servlet method, doGet() or doPost() to call. 

5. Then, to respond to the client, servlet uses response instance to write the response.

6.After the service( ) method is completed, container call the destroy( ) method. And the request and response instance are prepared for garbage collection.

Servlet API

there are 2 packages of java servlet API are as follow:

1.javax.servlet

This package contains several classes and interfaces that describe and define bonds between a class and environment for an object.

Interface: -

ServletResponse

ServletRequest

RequestDispatcher

ServletConfig

Servlet

Class: -

GenericServlet

ServletRequestWrapper

ServletResponseWrapper

ServletInputStream

ServletOutputStream

Exception

ServletException

UnavailableException

2.javax.servlet.http

This package contains several classes and interfaces that describe and define bonds between a servlet class running under HTTP protocol and environment for an object.

Interface:- 

HttpServletRequest

HttpServletResponse

HttpSession

HttpSessionContext

HttpSessionListener

Class: -

Cookie

HttpServlet

HttpServletRequestWrapper

HttpServletResponseWrapper

HttpSessionEvent