javax.servlet

Interface RequestDispatcher

All Known Implementing Classes:

RequestDispatcherImpl

public interface RequestDispatcher

The RequestDispatcher gives servlets the capabilities of SSI includes. The forwarded or included page is handled as a normal page request.

 RequestDispatcher disp;
 disp = request.getRequestDispatcher("inc.jsp?a=b");
 disp.include(request, response);
 

Servlets typically use ServletRequest.setAttribute() to communicate between included pages.

A popular architecture uses servlets to process the initial request and JSP files to format the results. That template architecture uses request attributes to communicate data from the servlet to the JSP page. disp.forward() transfers the request to the JSP file.

Field Summary

Fields

Modifier and Type	Field and Description
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

Modifier and Type	Method and Description
void	forward(ServletRequest request, ServletResponse response) Forwards the request to another page.
void	include(ServletRequest request, ServletResponse response) Includes the result of another page.

Field Detail

ERROR_MESSAGE

static final java.lang.String ERROR_MESSAGE

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Constant Field Values

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_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

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Constant Field Values

Method Detail

forward

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

Forwards the request to another page. Forward may not be called if data has been sent to the client. Specifically, forward calls the response.reset() method to clear the output buffer.

Query parameters are added to the original query parameters.

The new URI values are based on the RequestDispatcher URI. So getRequestURI(), getServletPath(), and getPathInfo() will reflect the request dispatcher URI.

Parameters:

request - the original request

response - the original response

Throws:

ServletException

java.io.IOException

include

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

Includes the result of another page.

Query parameters are added to the original query parameters.

The included request's URI methods reflect the original URI data. So getRequestURI() will return the URI sent by the browser.

Included pages should use request.getAttribute() to get the new URI values:

getRequestURI	javax.servlet.include.request_uri
getContextPath	javax.servlet.include.context_path
getServletPath	javax.servlet.include.servlet_path
getPathInfo	javax.servlet.include.path_info
getQueryString	javax.servlet.include.query_string

Parameters:

request - the original request

response - the original response

Throws:

ServletException

java.io.IOException