servlet interface generic servlet vs httpservlet class methods request response and java api

httpservlet httpservlet class httpservlet methods httpservlet java httpservlet api genericservlet vs httpservlet httpservlet jar httpservlet response genericservlet and httpservlet httpservlet request generic servlet servlet interface

Different ways of creating servlet:

         We can create a servlet class in the following three ways.

         1) By implementing our class from Servlet interface.

         2) By extending our class from Generic Servlet.

         3) By extending our class from Http Servlet. 

      we are extending generic servlet or httpservlet class is nothing but we are indirectly implementing servlet    interface.

Servlet Interface :(javax.servlet.*)

• Servlet Interface is Root of Servlet Programming

• Servlet Interface Contains Follwing methods

1.      init(parameters)

2.     service(ServletRequest req,ServletResponse res)

3.     destroy()

4.     getServletConfig()

5.     getServletInfo()

   Among all these above five methods first 3 methods are called life cycle of servlet

Generic Servlet :(javax.Servlet.Http.*)

    In Generic Serlvet Class Four methods of servlet interface are implemented and one method is not         implemented in generic servlet class. 

Syntax of Generic Servlet: 

import javax.servlet.*;

  public abstract class genericServlet implements Servlet,ServletConfig,Serializable

{

   public void init()

  {

   -------------

   -------------

  }

   public void destroy()

 {

  -------------

  -------------

 } 

service(req,res);

  public void getServletInfo()

 {

  ----------------

  ----------------

 }

}

HttpServlet (javax.Servlet.Http.*) :

         HttpServlet is Derived or Bottom Class of the Servlet Hierarchy. HttpServlet is contains all features that are in generic servlet class that are inherited to HttpServlet Class extra to that it contains Non Life cycle Service() Method and 7 DoXXX() methods(ie. doget(),dopost()..............) .

Internal Flow Of HttpServlet:

      public HttpServlet extends GenricServlet

    {

         public void init()

       {

         }

        public void init(ServletConfig sc)

        {

           -------------------

           ------------

           service(req,res);

         }

         public void service(ServletRequest req,ServletResponse res)

        {

          //conversion ServletRequest And ServletResponse to HttpServletRequest And //HttpServletResponse

           

      

           service(httpreq,httpres);

         }

         public void service(HttpServletRequest req,HttpServletResponse res)

        {

          //-------------

          //-------------

          }

       public void destroy()

        {

           //---------------------

          }

}