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* Copyright 2004 The Apache Software Foundation
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package javax.servlet;
import java.io.IOException;
/**
* 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 <code>RequestDispatcher</code> object,
* which is used as a wrapper around a server resource located
* at a particular path or given by a particular name.
*
* <p>This interface is intended to wrap servlets,
* but a servlet container can create <code>RequestDispatcher</code>
* objects to wrap any type of resource.
*
* @author Various
*
* @see ServletContext#getRequestDispatcher(java.lang.String)
* @see ServletContext#getNamedDispatcher(java.lang.String)
* @see ServletRequest#getRequestDispatcher(java.lang.String)
*/
public interface RequestDispatcher {
/**
* The name of the request attribute under which the original
* request URI is made available to the target of a
* {@link #forward(ServletRequest,ServletResponse) forward}
*/
static final String FORWARD_REQUEST_URI = "javax.servlet.forward.request_uri";
/**
* The name of the request attribute under which the original
* context path is made available to the target of a
* {@link #forward(ServletRequest,ServletResponse) forward}
*/
static final String FORWARD_CONTEXT_PATH = "javax.servlet.forward.context_path";
/**
* The name of the request attribute under which the original
* path info is made available to the target of a
* {@link #forward(ServletRequest,ServletResponse) forward}
*/
static final String FORWARD_PATH_INFO = "javax.servlet.forward.path_info";
/**
* The name of the request attribute under which the original
* servlet path is made available to the target of a
* {@link #forward(ServletRequest,ServletResponse) forward}
*/
static final String FORWARD_SERVLET_PATH = "javax.servlet.forward.servlet_path";
/**
* The name of the request attribute under which the original
* query string is made available to the target of a
* {@link #forward(ServletRequest,ServletResponse) forward}
*/
static final String FORWARD_QUERY_STRING = "javax.servlet.forward.query_string";
/**
* The name of the request attribute under which the request URI
* of the target of an {@link #include(ServletRequest,ServletResponse)
* include} is stored
*/
static final String INCLUDE_REQUEST_URI = "javax.servlet.include.request_uri";
/**
* The name of the request attribute under which the context path
* of the target of an {@link #include(ServletRequest,ServletResponse)
* include} is stored
*/
static final String INCLUDE_CONTEXT_PATH = "javax.servlet.include.context_path";
/**
* The name of the request attribute under which the path info
* of the target of an {@link #include(ServletRequest,ServletResponse)
* include} is stored
*/
static final String INCLUDE_PATH_INFO = "javax.servlet.include.path_info";
/**
* The name of the request attribute under which the servlet path
* of the target of an {@link #include(ServletRequest,ServletResponse)
* include} is stored
*/
static final String INCLUDE_SERVLET_PATH = "javax.servlet.include.servlet_path";
/**
* The name of the request attribute under which the query string
* of the target of an {@link #include(ServletRequest,ServletResponse)
* include} is stored
*/
static final String INCLUDE_QUERY_STRING = "javax.servlet.include.query_string";
/**
* The name of the request attribute under which the exception object
* is propagated during an error dispatch
*/
public static final String ERROR_EXCEPTION = "javax.servlet.error.exception";
/**
* The name of the request attribute under which the type of the
* exception object is propagated during an error dispatch
*/
public static final String ERROR_EXCEPTION_TYPE = "javax.servlet.error.exception_type";
/**
* The name of the request attribute under which the exception message
* is propagated during an error dispatch
*/
public static final String ERROR_MESSAGE = "javax.servlet.error.message";
/**
* The name of the request attribute under which the request URI
* whose processing caused the error is propagated during an error
* dispatch
*/
public static final String ERROR_REQUEST_URI = "javax.servlet.error.request_uri";
/**
* The name of the request attribute under which the name of the servlet
* in which the error occurred is propagated during an error dispatch
*/
public static final String ERROR_SERVLET_NAME = "javax.servlet.error.servlet_name";
/**
* The name of the request attribute under which the response status
* is propagated during an error dispatch
*/
public static final String ERROR_STATUS_CODE = "javax.servlet.error.status_code";
/**
* 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.
*
* <p>For a <code>RequestDispatcher</code> obtained via
* <code>getRequestDispatcher()</code>, the <code>ServletRequest</code>
* object has its path elements and parameters adjusted to match
* the path of the target resource.
*
* <p><code>forward</code> 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 <code>IllegalStateException</code>.
* Uncommitted output in the response buffer is automatically cleared
* before the forward.
*
* <p>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 {@link ServletRequestWrapper} or
* {@link ServletResponseWrapper} classes
* that wrap them.
*
* <p>This method sets the dispatcher type of the given request to
* <code>DispatcherType.FORWARD</code>.
*
* @param request a {@link ServletRequest} object that represents the
* request the client makes of the servlet
*
* @param response a {@link ServletResponse} object that represents
* the response the servlet returns to the client
*
* @throws ServletException if the target resource throws this exception
*
* @throws IOException if the target resource throws this exception
*
* @throws IllegalStateException if the response was already committed
*
* @see ServletRequest#getDispatcherType
*/
public void forward(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.
*
* <p>The {@link 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.
*
* <p>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 {@link ServletRequestWrapper} or
* {@link ServletResponseWrapper} classes that wrap them.
*
* <p>This method sets the dispatcher type of the given request to
* <code>DispatcherType.INCLUDE</code>.
*
* @param request a {@link ServletRequest} object that contains the
* client's request
*
* @param response a {@link ServletResponse} object that contains the
* servlet's response
*
* @throws ServletException if the included resource throws this
* exception
*
* @throws IOException if the included resource throws this exception
*
* @see ServletRequest#getDispatcherType
*/
public void include(ServletRequest request, ServletResponse response)
throws ServletException, IOException;
}