Servlet Tutorials

In this RequestDispatcher is an interface,which is implementation of an object to be dispatch request to any resources(such as HTML, Image, JSP, Servlet) on the server.

Methods of RequestDispatcher

RequestDispatcher interface provides two important methods

Method	Description
void forward(ServletRequest request, ServletResponse response)	forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server
void include(ServletRequest request, ServletResponse response)	includes the content of a resource (servlet, JSP page, HTML file) in the response

How to get an Object of RequestDispatcher

getRequestDispatcher() method of ServletRequest
 returns the object of RequestDispatcher.
RequestDispatcher rs = request.getRequestDispatcher(
"hello.html");
rs.forward(request,response);
RequestDispatcher detail and instantiation using forward
OR
RequestDispatcher rs = request.getRequestDispatcher(
"hello.html");
rs.include(request,response);
RequestDispatcher detail and instantiation using include

Example of RequestDispatcher

It is shown that you how RequestDispatcher and forward or include response of a resource in a Servlet.

We are using index.html to attained a username and password from the user, Validate Servlet will validate the password entered by the user,

Then after user has entered "manager" as password, then he will be forwarded to Welcome Servlet else the user will stay on the index.html page and an error message will be displayed.

Created files as follows:

index.html It will have form fields to get user information.
Validate.java It will validate the data entered by the user.
Welcome.java It will be the welcome page.
web.xml , It is deployment descriptor.

index.html

<form action="servlet1" method="post">
Name:<input type="text" name="userName"/><br/>
Password:<input type="password" name="userPass"/><br/>
<input type="submit" value="login"/>
</form>

Login.java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Login extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
		throws ServletException, IOException {
	response.setContentType("text/html");
	PrintWriter out = response.getWriter();
	String n=request.getParameter("userName");
	String p=request.getParameter("userPass");
	if(p.equals("servlet"){
		RequestDispatcher rd=request.getRequestDispatcher("servlet2");
		rd.forward(request, response);
	}
	else{
		out.print("Sorry UserName or Password Error!");
		RequestDispatcher rd=request.getRequestDispatcher("/index.html");
		rd.include(request, response);				
		}
	}
}

WelcomeServlet.java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class WelcomeServlet extends HttpServlet {
	public void doPost(HttpServletRequest request,
		HttpServletResponse response)
		throws ServletException, IOException {
	response.setContentType("text/html");
	PrintWriter out = response.getWriter();	
	String n=request.getParameter("userName");
	out.print("Welcome "+n);
	}
}

web.xml

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class WelcomeServlet extends HttpServlet {
	public void doPost(HttpServletRequest request,
		HttpServletResponse response)
		throws ServletException, IOException {
	response.setContentType("text/html");
	PrintWriter out = response.getWriter();	
	String n=request.getParameter("userName");
	out.print("Welcome "+n);
	}
}