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.

Author:

Various

See Also:

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

Field Summary

Fields

Modifier and Type	Field and Description
static String	ERROR_EXCEPTION The name of the request attribute under which the exception object is propagated during an error dispatch
static String	ERROR_EXCEPTION_TYPE The name of the request attribute under which the type of the exception object is propagated during an error dispatch
static String	ERROR_MESSAGE The name of the request attribute under which the exception message is propagated during an error dispatch
static String	ERROR_REQUEST_URI The name of the request attribute under which the request URI whose processing caused the error is propagated during an error dispatch
static String	ERROR_SERVLET_NAME The name of the request attribute under which the name of the servlet in which the error occurred is propagated during an error dispatch
static String	ERROR_STATUS_CODE The name of the request attribute under which the response status is propagated during an error dispatch
static String	FORWARD_CONTEXT_PATH The name of the request attribute under which the original context path is made available to the target of a forward
static String	FORWARD_PATH_INFO The name of the request attribute under which the original path info is made available to the target of a forward
static String	FORWARD_QUERY_STRING The name of the request attribute under which the original query string is made available to the target of a forward
static String	FORWARD_REQUEST_URI The name of the request attribute under which the original request URI is made available to the target of a forward
static String	FORWARD_SERVLET_PATH The name of the request attribute under which the original servlet path is made available to the target of a forward
static String	INCLUDE_CONTEXT_PATH The name of the request attribute under which the context path of the target of an include is stored
static String	INCLUDE_PATH_INFO The name of the request attribute under which the path info of the target of an include is stored
static String	INCLUDE_QUERY_STRING The name of the request attribute under which the query string of the target of an include is stored
static String	INCLUDE_REQUEST_URI The name of the request attribute under which the request URI of the target of an include is stored
static String	INCLUDE_SERVLET_PATH The name of the request attribute under which the servlet path of the target of an include is stored

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.

Field Detail

FORWARD_REQUEST_URI

static final String FORWARD_REQUEST_URI

The name of the request attribute under which the original request URI is made available to the target of a forward

See Also:

Constant Field Values

FORWARD_CONTEXT_PATH

static final String FORWARD_CONTEXT_PATH

The name of the request attribute under which the original context path is made available to the target of a forward

See Also:

Constant Field Values

FORWARD_PATH_INFO

static final String FORWARD_PATH_INFO

The name of the request attribute under which the original path info is made available to the target of a forward

See Also:

Constant Field Values

FORWARD_SERVLET_PATH

static final String FORWARD_SERVLET_PATH

The name of the request attribute under which the original servlet path is made available to the target of a forward

See Also:

Constant Field Values

FORWARD_QUERY_STRING

static final String FORWARD_QUERY_STRING

The name of the request attribute under which the original query string is made available to the target of a forward

See Also:

Constant Field Values

INCLUDE_REQUEST_URI

static final String INCLUDE_REQUEST_URI

The name of the request attribute under which the request URI of the target of an include is stored

See Also:

Constant Field Values

INCLUDE_CONTEXT_PATH

static final String INCLUDE_CONTEXT_PATH

The name of the request attribute under which the context path of the target of an include is stored

See Also:

Constant Field Values

INCLUDE_PATH_INFO

static final String INCLUDE_PATH_INFO

The name of the request attribute under which the path info of the target of an include is stored

See Also:

Constant Field Values

INCLUDE_SERVLET_PATH

static final String INCLUDE_SERVLET_PATH

The name of the request attribute under which the servlet path of the target of an include is stored

See Also:

Constant Field Values

INCLUDE_QUERY_STRING

static final String INCLUDE_QUERY_STRING

The name of the request attribute under which the query string of the target of an include is stored

See Also:

Constant Field Values

ERROR_EXCEPTION

static final String ERROR_EXCEPTION

The name of the request attribute under which the exception object is propagated during an error dispatch

See Also:

Constant Field Values

ERROR_EXCEPTION_TYPE

static final String ERROR_EXCEPTION_TYPE

The name of the request attribute under which the type of the exception object is propagated during an error dispatch

See Also:

Constant Field Values

ERROR_MESSAGE

static final String ERROR_MESSAGE

The name of the request attribute under which the exception message is propagated during an error dispatch

See Also:

Constant Field Values

ERROR_REQUEST_URI

static final String ERROR_REQUEST_URI

The name of the request attribute under which the request URI whose processing caused the error is propagated during an error dispatch

See Also:

Constant Field Values

ERROR_SERVLET_NAME

static final String ERROR_SERVLET_NAME

The name of the request attribute under which the name of the servlet in which the error occurred is propagated during an error dispatch

See Also:

Constant Field Values

ERROR_STATUS_CODE

static final String ERROR_STATUS_CODE

The name of the request attribute under which the response status is propagated during an error dispatch

See Also:

Constant Field Values

Method Detail

forward

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

This method sets the dispatcher type of the given request to DispatcherType.FORWARD.

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

IOException - if the target resource throws this exception

IllegalStateException - if the response was already committed

See Also:

ServletRequest.getDispatcherType()

include

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

This method sets the dispatcher type of the given request to DispatcherType.INCLUDE.

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

IOException - if the included resource throws this exception

See Also:

ServletRequest.getDispatcherType()