https://tomcat.apache.org/: jakarta.servlet package 
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 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
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 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package jakarta.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 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.

See Also:
/**
 * 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.
 *
 * @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 that should be set by the container when the forward(ServletRequest, ServletResponse) method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #forward(ServletRequest, ServletResponse)} method is
     * called. It provides the original value of a path-related property of the
     * request. See the chapter "Forwarded Request Parameters" in the Servlet
     * Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String FORWARD_REQUEST_URI = "jakarta.servlet.forward.request_uri";

    
The name of the request attribute that should be set by the container when the forward(ServletRequest, ServletResponse) method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #forward(ServletRequest, ServletResponse)} method is
     * called. It provides the original value of a path-related property of the
     * request. See the chapter "Forwarded Request Parameters" in the Servlet
     * Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String FORWARD_CONTEXT_PATH = "jakarta.servlet.forward.context_path";

    
The name of the request attribute that should be set by the container when the forward(ServletRequest, ServletResponse) method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details. 
Since:Servlet 4.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #forward(ServletRequest, ServletResponse)} method is
     * called. It provides the original value of a path-related property of the
     * request. See the chapter "Forwarded Request Parameters" in the Servlet
     * Specification for details.
     *
     * @since Servlet 4.0
     */
    static final String FORWARD_MAPPING = "jakarta.servlet.forward.mapping";

    
The name of the request attribute that should be set by the container when the forward(ServletRequest, ServletResponse) method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #forward(ServletRequest, ServletResponse)} method is
     * called. It provides the original value of a path-related property of the
     * request. See the chapter "Forwarded Request Parameters" in the Servlet
     * Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String FORWARD_PATH_INFO = "jakarta.servlet.forward.path_info";

    
The name of the request attribute that should be set by the container when the forward(ServletRequest, ServletResponse) method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #forward(ServletRequest, ServletResponse)} method is
     * called. It provides the original value of a path-related property of the
     * request. See the chapter "Forwarded Request Parameters" in the Servlet
     * Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String FORWARD_SERVLET_PATH = "jakarta.servlet.forward.servlet_path";

    
The name of the request attribute that should be set by the container when the forward(ServletRequest, ServletResponse) method is called. It provides the original value of a path-related property of the request. See the chapter "Forwarded Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #forward(ServletRequest, ServletResponse)} method is
     * called. It provides the original value of a path-related property of the
     * request. See the chapter "Forwarded Request Parameters" in the Servlet
     * Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String FORWARD_QUERY_STRING = "jakarta.servlet.forward.query_string";

    
The name of the request attribute that should be set by the container when the include(ServletRequest, ServletResponse) method is called on the RequestDispatcher obtained by a path and not by a name. It provides information on the path that was used to obtain the RequestDispatcher instance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #include(ServletRequest, ServletResponse)} method is
     * called on the {@code RequestDispatcher} obtained by a path and not by a
     * name. It provides information on the path that was used to obtain the
     * {@code RequestDispatcher} instance for this include call. See the chapter
     * "Included Request Parameters" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String INCLUDE_REQUEST_URI = "jakarta.servlet.include.request_uri";

    
The name of the request attribute that should be set by the container when the include(ServletRequest, ServletResponse) method is called on the RequestDispatcher obtained by a path and not by a name. It provides information on the path that was used to obtain the RequestDispatcher instance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #include(ServletRequest, ServletResponse)} method is
     * called on the {@code RequestDispatcher} obtained by a path and not by a
     * name. It provides information on the path that was used to obtain the
     * {@code RequestDispatcher} instance for this include call. See the chapter
     * "Included Request Parameters" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String INCLUDE_CONTEXT_PATH = "jakarta.servlet.include.context_path";

    
The name of the request attribute that should be set by the container when the include(ServletRequest, ServletResponse) method is called on the RequestDispatcher obtained by a path and not by a name. It provides information on the path that was used to obtain the RequestDispatcher instance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #include(ServletRequest, ServletResponse)} method is
     * called on the {@code RequestDispatcher} obtained by a path and not by a
     * name. It provides information on the path that was used to obtain the
     * {@code RequestDispatcher} instance for this include call. See the chapter
     * "Included Request Parameters" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String INCLUDE_PATH_INFO = "jakarta.servlet.include.path_info";

    
The name of the request attribute that should be set by the container when the include(ServletRequest, ServletResponse) method is called on the RequestDispatcher obtained by a path and not by a name. It provides information on the path that was used to obtain the RequestDispatcher instance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details. 
Since:Servlet 4.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #include(ServletRequest, ServletResponse)} method is
     * called on the {@code RequestDispatcher} obtained by a path and not by a
     * name. It provides information on the path that was used to obtain the
     * {@code RequestDispatcher} instance for this include call. See the chapter
     * "Included Request Parameters" in the Servlet Specification for details.
     *
     * @since Servlet 4.0
     */
    static final String INCLUDE_MAPPING = "jakarta.servlet.include.mapping";

    
The name of the request attribute that should be set by the container when the include(ServletRequest, ServletResponse) method is called on the RequestDispatcher obtained by a path and not by a name. It provides information on the path that was used to obtain the RequestDispatcher instance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #include(ServletRequest, ServletResponse)} method is
     * called on the {@code RequestDispatcher} obtained by a path and not by a
     * name. It provides information on the path that was used to obtain the
     * {@code RequestDispatcher} instance for this include call. See the chapter
     * "Included Request Parameters" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String INCLUDE_SERVLET_PATH = "jakarta.servlet.include.servlet_path";

    
The name of the request attribute that should be set by the container when the include(ServletRequest, ServletResponse) method is called on the RequestDispatcher obtained by a path and not by a name. It provides information on the path that was used to obtain the RequestDispatcher instance for this include call. See the chapter "Included Request Parameters" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when the {@link #include(ServletRequest, ServletResponse)} method is
     * called on the {@code RequestDispatcher} obtained by a path and not by a
     * name. It provides information on the path that was used to obtain the
     * {@code RequestDispatcher} instance for this include call. See the chapter
     * "Included Request Parameters" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    static final String INCLUDE_QUERY_STRING = "jakarta.servlet.include.query_string";

    
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of type java.lang.Throwable. See the chapter "Error Handling" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when custom error-handling servlet or JSP page is invoked. The value of
     * the attribute is of type {@code java.lang.Throwable}. See the chapter
     * "Error Handling" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    public static final String ERROR_EXCEPTION = "jakarta.servlet.error.exception";

    
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of type java.lang.Class. See the chapter "Error Handling" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when custom error-handling servlet or JSP page is invoked. The value of
     * the attribute is of type {@code java.lang.Class}. See the chapter
     * "Error Handling" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    public static final String ERROR_EXCEPTION_TYPE = "jakarta.servlet.error.exception_type";

    
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of type java.lang.String. See the chapter "Error Handling" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when custom error-handling servlet or JSP page is invoked. The value of
     * the attribute is of type {@code java.lang.String}. See the chapter
     * "Error Handling" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    public static final String ERROR_MESSAGE = "jakarta.servlet.error.message";

    
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of type java.lang.String. See the chapter "Error Handling" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when custom error-handling servlet or JSP page is invoked. The value of
     * the attribute is of type {@code java.lang.String}. See the chapter
     * "Error Handling" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    public static final String ERROR_REQUEST_URI = "jakarta.servlet.error.request_uri";

    
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of type java.lang.String. See the chapter "Error Handling" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when custom error-handling servlet or JSP page is invoked. The value of
     * the attribute is of type {@code java.lang.String}. See the chapter
     * "Error Handling" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    public static final String ERROR_SERVLET_NAME = "jakarta.servlet.error.servlet_name";

    
The name of the request attribute that should be set by the container when custom error-handling servlet or JSP page is invoked. The value of the attribute is of type java.lang.Integer. See the chapter "Error Handling" in the Servlet Specification for details. 
Since:Servlet 3.0
/**
     * The name of the request attribute that should be set by the container
     * when custom error-handling servlet or JSP page is invoked. The value of
     * the attribute is of type {@code java.lang.Integer}. See the chapter
     * "Error Handling" in the Servlet Specification for details.
     *
     * @since Servlet 3.0
     */
    public static final String ERROR_STATUS_CODE = "jakarta.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.


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. 
Params:
  • 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:
/**
     * 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.
     *
     *
     * @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
     *
     * @exception ServletException
     *                if the target resource throws this exception
     *
     * @exception IOException
     *                if the target resource throws this exception
     *
     * @exception IllegalStateException
     *                if the response was already committed
     */
    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.

 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. 
Params:
Throws:
/**
     * 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.
     *
     * @param request
     *            a {@link ServletRequest} object that contains the client's
     *            request
     *
     * @param response
     *            a {@link ServletResponse} object that contains the servlet's
     *            response
     *
     * @exception ServletException
     *                if the included resource throws this exception
     *
     * @exception IOException
     *                if the included resource throws this exception
     */
    public void include(ServletRequest request, ServletResponse response)
            throws ServletException, IOException;
}