javax.servlet

Interface RequestDispatcher

public interface RequestDispatcher

Defines an object that receives requests from the client and sends them to any resource (such as a servlet, HTML file, or JSP file) on the server. The servlet container creates the RequestDispatcher object, which is used as a wrapper around a server resource located at a particular path or given by a particular name.

This interface is intended to wrap servlets, but a servlet container can create RequestDispatcher objects to wrap any type of resource.

Version:

$Version$

Author:

Various

See Also:

ServletContext.getRequestDispatcher(java.lang.String), ServletContext.getNamedDispatcher(java.lang.String), ServletRequest.getRequestDispatcher(java.lang.String)

Method Summary

Methods

Modifier and Type	Method and 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.

Method Detail

forward

void forward(ServletRequest request,
           ServletResponse response)
             throws ServletException,
                    java.io.IOException

Forwards a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server. This method allows one servlet to do preliminary processing of a request and another resource to generate the response.

For a RequestDispatcher obtained via getRequestDispatcher(), the ServletRequest object has its path elements and parameters adjusted to match the path of the target resource.

forward should be called before the response has been committed to the client (before response body output has been flushed). If the response already has been committed, this method throws an IllegalStateException. Uncommitted output in the response buffer is automatically cleared before the forward.

The request and response parameters must be either the same objects as were passed to the calling servlet's service method or be subclasses of the ServletRequestWrapper or ServletResponseWrapper classes that wrap them.

Parameters:

request - a ServletRequest object that represents the request the client makes of the servlet

response - a ServletResponse object that represents the response the servlet returns to the client

Throws:

ServletException - if the target resource throws this exception

java.io.IOException - if the target resource throws this exception

java.lang.IllegalStateException - if the response was already committed

include

void include(ServletRequest request,
           ServletResponse response)
             throws ServletException,
                    java.io.IOException

Includes the content of a resource (servlet, JSP page, HTML file) in the response. In essence, this method enables programmatic server-side includes.

The ServletResponse object has its path elements and parameters remain unchanged from the caller's. The included servlet cannot change the response status code or set headers; any attempt to make a change is ignored.

The request and response parameters must be either the same objects as were passed to the calling servlet's service method or be subclasses of the ServletRequestWrapper or ServletResponseWrapper classes that wrap them.

Parameters:

request - a ServletRequest object that contains the client's request

response - a ServletResponse object that contains the servlet's response

Throws:

ServletException - if the included resource throws this exception

java.io.IOException - if the included resource throws this exception