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)

Field Summary

static java.lang.String	ERROR_EXCEPTION
static java.lang.String	ERROR_EXCEPTION_TYPE
static java.lang.String	ERROR_MESSAGE
static java.lang.String	ERROR_REQUEST_URI
static java.lang.String	ERROR_SERVLET_NAME
static java.lang.String	ERROR_STATUS_CODE
static java.lang.String	FORWARD_CONTEXT_PATH
static java.lang.String	FORWARD_PATH_INFO
static java.lang.String	FORWARD_QUERY_STRING
static java.lang.String	FORWARD_REQUEST_URI
static java.lang.String	FORWARD_SERVLET_PATH
static java.lang.String	INCLUDE_CONTEXT_PATH
static java.lang.String	INCLUDE_PATH_INFO
static java.lang.String	INCLUDE_QUERY_STRING
static java.lang.String	INCLUDE_REQUEST_URI
static java.lang.String	INCLUDE_SERVLET_PATH

Method Summary

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.

Field Detail

ERROR_EXCEPTION

static final java.lang.String ERROR_EXCEPTION

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Constant Field Values

ERROR_EXCEPTION_TYPE

static final java.lang.String ERROR_EXCEPTION_TYPE

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Constant Field Values

ERROR_MESSAGE

static final java.lang.String ERROR_MESSAGE

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Constant Field Values

ERROR_REQUEST_URI

static final java.lang.String ERROR_REQUEST_URI

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Constant Field Values

ERROR_SERVLET_NAME

static final java.lang.String ERROR_SERVLET_NAME

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Constant Field Values

ERROR_STATUS_CODE

static final java.lang.String ERROR_STATUS_CODE

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Constant Field Values

FORWARD_CONTEXT_PATH

static final java.lang.String FORWARD_CONTEXT_PATH

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Constant Field Values

FORWARD_PATH_INFO

static final java.lang.String FORWARD_PATH_INFO

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Constant Field Values

FORWARD_QUERY_STRING

static final java.lang.String FORWARD_QUERY_STRING

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Constant Field Values

FORWARD_REQUEST_URI

static final java.lang.String FORWARD_REQUEST_URI

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Constant Field Values

FORWARD_SERVLET_PATH

static final java.lang.String FORWARD_SERVLET_PATH

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Constant Field Values

INCLUDE_CONTEXT_PATH

static final java.lang.String INCLUDE_CONTEXT_PATH

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Constant Field Values

INCLUDE_PATH_INFO

static final java.lang.String INCLUDE_PATH_INFO

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Constant Field Values

INCLUDE_QUERY_STRING

static final java.lang.String INCLUDE_QUERY_STRING

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Constant Field Values

INCLUDE_REQUEST_URI

static final java.lang.String INCLUDE_REQUEST_URI

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Constant Field Values

INCLUDE_SERVLET_PATH

static final java.lang.String INCLUDE_SERVLET_PATH

See Also:

Constant Field Values

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