A RequestDispatcher instance allows one servlet to invoke another and either forward a request, or include the target servlet’s response with its own. The RequestDispatcher interface provides methods to accomplish both. To obtain an object that implements the RequestDispatcher interface, use one of these ServletContext methods:
getRequestDispatcher(<URL map to resource>)
getNamedDispatcher(<servlet name>)
To forward a request, the initial servlet calls the forward method of the RequestDispatcher interface. The target servlet returns the response. This method can be called only if no output has been committed to the client. Before the forward method returns, the response must be committed and closed by the servlet container.
To include a target servlet’s response with its own, the initial servlet calls the include method of the RequestDispatcher interface. The target servlet has full access to the request object but can write only to the ServletOutputStream or Writer of the response object and it cannot modify the response headers. The target servlet can commit a response by either writing past the end of the response buffer, or explicitly calling the flush method of the ServletResponse interface.
