The RequestDispatcher interface provides facilities for dispatching requests between resources like servlets, JSPs, and HTML files. It has two main methods: forward() dispatches a request to another resource and the response replaces the current response, while include() dispatches a request and includes the response in the current response. For example, a servlet could validate user input, and if valid forward the request to a JSP welcome page via the RequestDispatcher, or include error messages on the same page if invalid.

1. Enterprise Java
Unit-2
Chapter-1
• Request Dispatcher
By
Prof. Sandeep Vishwakarma

2. Request Dispatcher
• The RequestDispatcher interface
provides the facility of dispatching
the request to another resource it may
be html, servlet or jsp. This interface
can also be used to include the
content of another resource also. It is
one of the way of servlet
collaboration.

3. RequestDispatcher Methods
Methods Description
forward() Forwards a request from a servlet to
another resource such as Servlet, JSP
or HTML file on the server.
include() Includes the content of a resource
such as Servlet, JSP, HTML file in the
response.
The RequestDispatcher interface provides two methods.

4. response of second servlet is sent to the client. Response
of the first servlet is not displayed to the user.

5. response of second servlet is included in the response of
the first servlet that is being sent to the client.

6. How to get an Object of RequestDispatcher
getRequestDispatcher() method of ServletRequest returns
the object of RequestDispatcher.

8. Demonstration of RequestDispatcher
• index.html will have form fields to get user
information.
• Validate.java will validate the data entered by
the user.
• Welcome.java will be the welcome page.
• web.xml , the deployment descriptor.

9. index.html
<form method="post" action="Validate">
Name:<input type="text" name="user" /><br/>
Password:<input type="password" name="pass“><br/>
<input type="submit" value="submit">
</form>

10. import java.io.*;
import javax.servlet.*;
public class Validate extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
String name = request.getParameter("user");
String password = request.getParameter("pass");
if(password.equals(“cbscollege"))
{
RequestDispatcher rd = request.getRequestDispatcher("Welcome");
rd.forward(request, response);
} else
{
out.println("<font color='red'><b>You have entered incorrect
password</b></font>");
RequestDispatcher rd = request.getRequestDispatcher("index.html");
rd.include(request, response);
} }
finally {
out.close();
} } }
Validate.java

11. Welcome.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Welcome extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
out.println("<h2>Welcome user</h2>");
}
finally {
out.close();
}
}
}

12. Out put