hi,

The main use of RequestDispatcher is when u want to transfer
control from one webapplication to another webapplication
deployed in same server(its web/ app server). 

If you want to transfer control from one webapplication to
another webapplication those are deployed in different
servers( Ex one in Tomcat, another in Weblogic) use
response.sendRedirect("url"); method.

if u want any confirmation please call me.

my mobile no is 09096272808

The main use of Request Dispatcher Objest is to share 
request object between two servlets

RequestDispatch is mainly used to shipping request 
attributes from one servlet/jsp to another servlet/jsp. 
While doing this we first create RequestDispatch instance 
with string url as parameter to where request data to be 
shipped. Then we cal reqDispatchReference.forward
(request,response) method. This is something like assigning 
work to third party.
Ex:(to forward request data from Servlet1 to page2.jsp)
class Servlet1 extends HttpServlet{
public void service(... request,... response){
...........
RequestDispatcher rd=request.RequestDispatcher("page2.jsp");
try
{
rd.forward(request,response);
}
catch(Exception e)
{
}
}
}