RequestDispatcher and Page Redirection in Servlets

Introduction

The RequestDispatcher is an interface that defines an object to receive request from the client and sends them to any resource on the server.
It implements an object to wrap together different types of resources in Servlet container.

RequestDispatcher Methods

The RequestDispatcher interface provides two methods:

Methods	Description
public void forward(ServletRequest request, ServletResponse response)	It forwards a client request from a servlet to another resource (servlet, JSP file, HTML file) on the server.
public void include(ServletRequest request, ServletResponse response)	Includes the content of a resource (Servlet, JSP pages, HTML file) in the response.

Getting the Object of RequestDispatcher

ServletRequest interface provides the getRequestDispatcher( ) method to returns the object of RequestDispatcher.

Example

RequestDispatcher rd = request.getRequestDispatcher("index.html");
rd.forward(request, response);

OR

RequestDispatcher rd = request.getRequestDispatcher("index.html");
rd.include(request, response);

Page Redirection

The Page redirection is the process of redirecting the response to another resource.
It is used to move the document to the new location for load balancing or simple randomization.
The sendRedirect( ) method is the method of HttpServletResponse interface.
It is used to redirect response to another resource (servlet, jsp or HTML file).

For example:
response.sendRedirect("index.html");

Difference between forward( ) method and sendRedirect( ) method

forward( )	sendRedirect( )
Used to forward the resources available within the server.	Used to redirect the resources to different servers or domains.
The forward( ) method is executed on the server side.	The sentRedirect( ) method is executed on the client side.
The forward( ) method is faster than sendRedirect( ).	It is slower because each time a new request is created, old one is lost.
The transfer of control is done by container and client/browser is not involved.	The transfer of control is assigned to the browser and a new request to the given URL is initiated.
The request is shared by the target resource.	New request is created for the server resource.
It is declared in RequestDispatcher interface.	It is declared in HttpServletResponse.

Example : Illustrating the sendRedirect( ) method for page redirecting in Servlet

//SendRedirectDemo.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class SendRedirectDemo extends HttpServlet
{
     protected void doGet(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException
     {
          response.setContentType("text/html");
          PrintWriter pw = response.getWriter();
          response.sendRedirect("http://tutorialride.com/")
          pw.close();
     }
}