what is requestDispatcher

what is the difference b/w sendRedirect and requestDispatcher

a request dispatcher implements the RequestDispatcher interface, which contains methods to dispatch a request. Methods like sendRedirect, forward... Check it at http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/RequestDispatcher.html

Dharmender Singh,
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in send redirect the new response object will be sent but in forward coming req res objects will be forwarded

There is no need to post the same message twice.In case you have done os , you can delete one of the messages.

sendRedirect works on the client side.The server sends the browser the URL to which it needs to connect.The browser then makes a fresh connection with the URL.

RequestDispatcher works on the server side.Look for servlet documentation for more information.

Try searching javaranch .This questions has been asked quite a few times before too.