File: ServletRequest.java

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/*
 * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed 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
 *
 * Unless required by applicable law or agreed to in writing, software
 * 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 javax.servlet;

import java.io.*;
import java.util.*;

/**
 * Defines an object to provide client request information to a servlet.  The
 * servlet container creates a <code>ServletRequest</code> object and passes
 * it as an argument to the servlet's <code>service</code> method.
 *
 * <p>A <code>ServletRequest</code> object provides data including
 * parameter name and values, attributes, and an input stream.
 * Interfaces that extend <code>ServletRequest</code> can provide
 * additional protocol-specific data (for example, HTTP data is
 * provided by {@link javax.servlet.http.HttpServletRequest}.
 * 
 * @author Various
 *
 * @see javax.servlet.http.HttpServletRequest
 *
 */
public interface ServletRequest {

    /**
     * Returns the value of the named attribute as an <code>Object</code>,
     * or <code>null</code> if no attribute of the given name exists. 
     *
     * <p> Attributes can be set two ways.  The servlet container may set
     * attributes to make available custom information about a request.
     * For example, for requests made using HTTPS, the attribute
     * <code>javax.servlet.request.X509Certificate</code> can be used to
     * retrieve information on the certificate of the client.  Attributes
     * can also be set programatically using 
     * {@link ServletRequest#setAttribute}.  This allows information to be
     * embedded into a request before a {@link RequestDispatcher} call.
     *
     * <p>Attribute names should follow the same conventions as package
     * names. This specification reserves names matching <code>java.*</code>,
     * <code>javax.*</code>, and <code>sun.*</code>. 
     *
     * @param name a <code>String</code> specifying the name of the attribute
     *
     * @return an <code>Object</code> containing the value of the attribute,
     * or <code>null</code> if the attribute does not exist
     */
    public Object getAttribute(String name);
    
    /**
     * Returns an <code>Enumeration</code> containing the
     * names of the attributes available to this request. 
     * This method returns an empty <code>Enumeration</code>
     * if the request has no attributes available to it.
     * 
     * @return an <code>Enumeration</code> of strings containing the names 
     * of the request's attributes
     */
    public Enumeration<String> getAttributeNames();
    
    /**
     * Returns the name of the character encoding used in the body of this
     * request. This method returns <code>null</code> if no request encoding
     * character encoding has been specified. The following methods for
     * specifying the request character encoding are consulted, in decreasing
     * order of priority: per request, per web app (using
     * {@link ServletContext#setRequestCharacterEncoding}, deployment
     * descriptor), and per container (for all web applications deployed in 
     * that container, using vendor specific configuration).
     * 
     * @return a <code>String</code> containing the name of the character
     * encoding, or <code>null</code> if the request does not specify a
     * character encoding
     */
    public String getCharacterEncoding();

    /**
     * Overrides the name of the character encoding used in the body of this
     * request. This method must be called prior to reading request parameters
     * or reading input using getReader(). Otherwise, it has no effect.
     * 
     * @param env <code>String</code> containing the name of
     * the character encoding.
     *
     * @throws UnsupportedEncodingException if this ServletRequest is still
     * in a state where a character encoding may be set,
     * but the specified encoding is invalid
     */
    public void setCharacterEncoding(String env) throws UnsupportedEncodingException;

    /**
     * Returns the length, in bytes, of the request body and made available by
     * the input stream, or -1 if the length is not known ir is greater than
     * Integer.MAX_VALUE. For HTTP servlets,
     * same as the value of the CGI variable CONTENT_LENGTH.
     *
     * @return an integer containing the length of the request body or -1 if
     * the length is not known or is greater than Integer.MAX_VALUE.
     */
    public int getContentLength();
    
    /**
     * Returns the length, in bytes, of the request body and made available by
     * the input stream, or -1 if the length is not known. For HTTP servlets,
     * same as the value of the CGI variable CONTENT_LENGTH.
     *
     * @return a long containing the length of the request body or -1L if
     * the length is not known
     *
     * @since Servlet 3.1
     */
    default public long getContentLengthLong() { return getContentLength(); }
    
    /**
     * Returns the MIME type of the body of the request, or 
     * <code>null</code> if the type is not known. For HTTP servlets, 
     * same as the value of the CGI variable CONTENT_TYPE.
     *
     * @return a <code>String</code> containing the name of the MIME type
     * of the request, or null if the type is not known
     */
    public String getContentType();
    
    /**
     * Retrieves the body of the request as binary data using
     * a {@link ServletInputStream}.  Either this method or 
     * {@link #getReader} may be called to read the body, not both.
     *
     * @return a {@link ServletInputStream} object containing
     * the body of the request
     *
     * @exception IllegalStateException if the {@link #getReader} method
     * has already been called for this request
     *
     * @exception IOException if an input or output exception occurred
     */
    public ServletInputStream getInputStream() throws IOException; 
     
    /**
     * Returns the value of a request parameter as a <code>String</code>,
     * or <code>null</code> if the parameter does not exist. Request parameters
     * are extra information sent with the request.  For HTTP servlets,
     * parameters are contained in the query string or posted form data.
     *
     * <p>You should only use this method when you are sure the
     * parameter has only one value. If the parameter might have
     * more than one value, use {@link #getParameterValues}.
     *
     * <p>If you use this method with a multivalued
     * parameter, the value returned is equal to the first value
     * in the array returned by <code>getParameterValues</code>.
     *
     * <p>If the parameter data was sent in the request body, such as occurs
     * with an HTTP POST request, then reading the body directly via {@link
     * #getInputStream} or {@link #getReader} can interfere
     * with the execution of this method.
     *
     * @param name a <code>String</code> specifying the name of the parameter
     *
     * @return a <code>String</code> representing the single value of
     * the parameter
     *
     * @see #getParameterValues
     */
    public String getParameter(String name);
    
    /**
     *
     * Returns an <code>Enumeration</code> of <code>String</code>
     * objects containing the names of the parameters contained
     * in this request. If the request has 
     * no parameters, the method returns an empty <code>Enumeration</code>. 
     *
     * @return an <code>Enumeration</code> of <code>String</code>
     * objects, each <code>String</code> containing the name of
     * a request parameter; or an empty <code>Enumeration</code>
     * if the request has no parameters
     */
    public Enumeration<String> getParameterNames();
        
    /**
     * Returns an array of <code>String</code> objects containing 
     * all of the values the given request parameter has, or 
     * <code>null</code> if the parameter does not exist.
     *
     * <p>If the parameter has a single value, the array has a length
     * of 1.
     *
     * @param name a <code>String</code> containing the name of 
     * the parameter whose value is requested
     *
     * @return an array of <code>String</code> objects 
     * containing the parameter's values
     *
     * @see #getParameter
     */
    public String[] getParameterValues(String name);
 
    /**
     * Returns a java.util.Map of the parameters of this request.
     * 
     * <p>Request parameters are extra information sent with the request.
     * For HTTP servlets, parameters are contained in the query string or
     * posted form data.
     *
     * @return an immutable java.util.Map containing parameter names as 
     * keys and parameter values as map values. The keys in the parameter
     * map are of type String. The values in the parameter map are of type
     * String array.
     */
    public Map<String, String[]> getParameterMap();
    
    /**
     * Returns the name and version of the protocol the request uses
     * in the form <i>protocol/majorVersion.minorVersion</i>, for 
     * example, HTTP/1.1. For HTTP servlets, the value
     * returned is the same as the value of the CGI variable 
     * <code>SERVER_PROTOCOL</code>.
     *
     * @return a <code>String</code> containing the protocol 
     * name and version number
     */    
    public String getProtocol();
    
    /**
     * Returns the name of the scheme used to make this request, 
     * for example,
     * <code>http</code>, <code>https</code>, or <code>ftp</code>.
     * Different schemes have different rules for constructing URLs,
     * as noted in RFC 1738.
     *
     * @return a <code>String</code> containing the name 
     * of the scheme used to make this request
     */
    public String getScheme();
    
    /**
     * Returns the host name of the server to which the request was sent.
     * It is the value of the part before ":" in the <code>Host</code>
     * header value, if any, or the resolved server name, or the server IP
     * address.
     *
     * @return a <code>String</code> containing the name of the server
     */
    public String getServerName();
    
    /**
     * Returns the port number to which the request was sent.
     * It is the value of the part after ":" in the <code>Host</code>
     * header value, if any, or the server port where the client connection
     * was accepted on.
     *
     * @return an integer specifying the port number
     */
    public int getServerPort();
    
    /**
     * Retrieves the body of the request as character data using
     * a <code>BufferedReader</code>.  The reader translates the character
     * data according to the character encoding used on the body.
     * Either this method or {@link #getInputStream} may be called to read the
     * body, not both.
     * 
     * @return a <code>BufferedReader</code> containing the body of the request 
     *
     * @exception UnsupportedEncodingException  if the character set encoding
     * used is not supported and the text cannot be decoded
     *
     * @exception IllegalStateException if {@link #getInputStream} method
     * has been called on this request
     *
     * @exception IOException if an input or output exception occurred
     *
     * @see #getInputStream
     */
    public BufferedReader getReader() throws IOException;
    
    /**
     * Returns the Internet Protocol (IP) address of the client 
     * or last proxy that sent the request.
     * For HTTP servlets, same as the value of the 
     * CGI variable <code>REMOTE_ADDR</code>.
     *
     * @return a <code>String</code> containing the 
     * IP address of the client that sent the request
     */
    public String getRemoteAddr();
    
    /**
     * Returns the fully qualified name of the client
     * or the last proxy that sent the request.
     * If the engine cannot or chooses not to resolve the hostname 
     * (to improve performance), this method returns the dotted-string form of 
     * the IP address. For HTTP servlets, same as the value of the CGI variable 
     * <code>REMOTE_HOST</code>.
     *
     * @return a <code>String</code> containing the fully 
     * qualified name of the client
     */
    public String getRemoteHost();
    
    /**
     * Stores an attribute in this request.
     * Attributes are reset between requests.  This method is most
     * often used in conjunction with {@link RequestDispatcher}.
     *
     * <p>Attribute names should follow the same conventions as
     * package names. Names beginning with <code>java.*</code>,
     * <code>javax.*</code>, and <code>com.sun.*</code>, are
     * reserved for use by Sun Microsystems.
     *<br> If the object passed in is null, the effect is the same as
     * calling {@link #removeAttribute}.
     * <br> It is warned that when the request is dispatched from the
     * servlet resides in a different web application by
     * <code>RequestDispatcher</code>, the object set by this method
     * may not be correctly retrieved in the caller servlet.
     *
     * @param name a <code>String</code> specifying 
     * the name of the attribute
     *
     * @param o the <code>Object</code> to be stored
     *
     */
    public void setAttribute(String name, Object o);
    
    /**
     *
     * Removes an attribute from this request.  This method is not
     * generally needed as attributes only persist as long as the request
     * is being handled.
     *
     * <p>Attribute names should follow the same conventions as
     * package names. Names beginning with <code>java.*</code>,
     * <code>javax.*</code>, and <code>com.sun.*</code>, are
     * reserved for use by Sun Microsystems.
     *
     * @param name a <code>String</code> specifying 
     * the name of the attribute to remove
     */
    public void removeAttribute(String name);
    
    /**
     * Returns the preferred <code>Locale</code> that the client will 
     * accept content in, based on the Accept-Language header.
     * If the client request doesn't provide an Accept-Language header,
     * this method returns the default locale for the server.
     *
     * @return the preferred <code>Locale</code> for the client
     */
    public Locale getLocale();
    
    /**
     * Returns an <code>Enumeration</code> of <code>Locale</code> objects
     * indicating, in decreasing order starting with the preferred locale, the
     * locales that are acceptable to the client based on the Accept-Language
     * header.
     * If the client request doesn't provide an Accept-Language header,
     * this method returns an <code>Enumeration</code> containing one 
     * <code>Locale</code>, the default locale for the server.
     *
     * @return an <code>Enumeration</code> of preferred 
     * <code>Locale</code> objects for the client
     */
    public Enumeration<Locale> getLocales();
    
    /**
     *
     * Returns a boolean indicating whether this request was made using a
     * secure channel, such as HTTPS.
     *
     * @return a boolean indicating if the request was made using a
     * secure channel
     */
    public boolean isSecure();
    
    /**
     *
     * Returns a {@link RequestDispatcher} object that acts as a wrapper for
     * the resource located at the given path.  
     * A <code>RequestDispatcher</code> object can be used to forward
     * a request to the resource or to include the resource in a response.
     * The resource can be dynamic or static.
     *
     * <p>The pathname specified may be relative, although it cannot extend
     * outside the current servlet context.  If the path begins with 
     * a "/" it is interpreted as relative to the current context root.  
     * This method returns <code>null</code> if the servlet container
     * cannot return a <code>RequestDispatcher</code>.
     *
     * <p>The difference between this method and {@link
     * ServletContext#getRequestDispatcher} is that this method can take a
     * relative path.
     *
     * @param path a <code>String</code> specifying the pathname
     * to the resource. If it is relative, it must be
     * relative against the current servlet.
     *
     * @return a <code>RequestDispatcher</code> object that acts as a
     * wrapper for the resource at the specified path,
     * or <code>null</code> if the servlet container cannot
     * return a <code>RequestDispatcher</code>
     *
     * @see RequestDispatcher
     * @see ServletContext#getRequestDispatcher
     */
    public RequestDispatcher getRequestDispatcher(String path);
    
    /**
     * @param path the path for which the real path is to be returned.

     * @return the <i>real</i> path, or <tt>null</tt> if the
     * translation cannot be performed.

     * @deprecated  As of Version 2.1 of the Java Servlet API,
     *    use {@link ServletContext#getRealPath} instead.
     */
    public String getRealPath(String path);
    
    /**
     * Returns the Internet Protocol (IP) source port of the client
     * or last proxy that sent the request.
     *
     * @return an integer specifying the port number
     *
     * @since Servlet 2.4
     */    
    public int getRemotePort();

    /**
     * Returns the host name of the Internet Protocol (IP) interface on
     * which the request was received.
     *
     * @return a <code>String</code> containing the host
     *         name of the IP on which the request was received.
     *
     * @since Servlet 2.4
     */
    public String getLocalName();

    /**
     * Returns the Internet Protocol (IP) address of the interface on
     * which the request  was received.
     *
     * @return a <code>String</code> containing the
     * IP address on which the request was received. 
     *
     * @since Servlet 2.4
     */       
    public String getLocalAddr();

    /**
     * Returns the Internet Protocol (IP) port number of the interface
     * on which the request was received.
     *
     * @return an integer specifying the port number
     *
     * @since Servlet 2.4
     */
    public int getLocalPort();

    /**
     * Gets the servlet context to which this ServletRequest was last
     * dispatched.
     *
     * @return the servlet context to which this ServletRequest was last
     * dispatched
     *
     * @since Servlet 3.0
     */
    default public ServletContext getServletContext() { return null; }

    /**
     * Puts this request into asynchronous mode, and initializes its
     * {@link AsyncContext} with the original (unwrapped) ServletRequest
     * and ServletResponse objects.
     *
     * <p>Calling this method will cause committal of the associated
     * response to be delayed until {@link AsyncContext#complete} is
     * called on the returned {@link AsyncContext}, or the asynchronous
     * operation has timed out.
     *
     * <p>Calling {@link AsyncContext#hasOriginalRequestAndResponse()} on
     * the returned AsyncContext will return <code>true</code>. Any filters
     * invoked in the <i>outbound</i> direction after this request was put
     * into asynchronous mode may use this as an indication that any request
     * and/or response wrappers that they added during their <i>inbound</i>
     * invocation need not stay around for the duration of the asynchronous
     * operation, and therefore any of their associated resources may be
     * released.
     *
     * <p>This method clears the list of {@link AsyncListener} instances
     * (if any) that were registered with the AsyncContext returned by the
     * previous call to one of the startAsync methods, after calling each
     * AsyncListener at its {@link AsyncListener#onStartAsync onStartAsync}
     * method.
     *
     * <p>Subsequent invocations of this method, or its overloaded 
     * variant, will return the same AsyncContext instance, reinitialized
     * as appropriate.
     *
     * @return the (re)initialized AsyncContext
     * 
     * @throws IllegalStateException if this request is within the scope of
     * a filter or servlet that does not support asynchronous operations
     * (that is, {@link #isAsyncSupported} returns false),
     * or if this method is called again without any asynchronous dispatch
     * (resulting from one of the {@link AsyncContext#dispatch} methods),
     * is called outside the scope of any such dispatch, or is called again
     * within the scope of the same dispatch, or if the response has
     * already been closed
     *
     * @see AsyncContext#dispatch()
     * @since Servlet 3.0
     */
    default public AsyncContext startAsync() throws IllegalStateException { return null; }
 
    /**
     * Puts this request into asynchronous mode, and initializes its
     * {@link AsyncContext} with the given request and response objects.
     *
     * <p>The ServletRequest and ServletResponse arguments must be
     * the same instances, or instances of {@link ServletRequestWrapper} and
     * {@link ServletResponseWrapper} that wrap them, that were passed to the
     * {@link Servlet#service service} method of the Servlet or the
     * {@link Filter#doFilter doFilter} method of the Filter, respectively,
     * in whose scope this method is being called.
     *
     * <p>Calling this method will cause committal of the associated
     * response to be delayed until {@link AsyncContext#complete} is
     * called on the returned {@link AsyncContext}, or the asynchronous
     * operation has timed out.
     *
     * <p>Calling {@link AsyncContext#hasOriginalRequestAndResponse()} on
     * the returned AsyncContext will return <code>false</code>,
     * unless the passed in ServletRequest and ServletResponse arguments
     * are the original ones or do not carry any application-provided wrappers.
     * Any filters invoked in the <i>outbound</i> direction after this
     * request was put into asynchronous mode may use this as an indication
     * that some of the request and/or response wrappers that they added
     * during their <i>inbound</i> invocation may need to stay in place for
     * the duration of the asynchronous operation, and their associated
     * resources may not be released.
     * A ServletRequestWrapper applied during the <i>inbound</i>
     * invocation of a filter may be released by the <i>outbound</i>
     * invocation of the filter only if the given <code>servletRequest</code>,
     * which is used to initialize the AsyncContext and will be returned by
     * a call to {@link AsyncContext#getRequest()}, does not contain said
     * ServletRequestWrapper. The same holds true for ServletResponseWrapper
     * instances. 
     *
     * <p>This method clears the list of {@link AsyncListener} instances
     * (if any) that were registered with the AsyncContext returned by the
     * previous call to one of the startAsync methods, after calling each
     * AsyncListener at its {@link AsyncListener#onStartAsync onStartAsync}
     * method.
     *
     * <p>Subsequent invocations of this method, or its zero-argument
     * variant, will return the same AsyncContext instance, reinitialized
     * as appropriate. If a call to this method is followed by a call to its
     * zero-argument variant, the specified (and possibly wrapped) request
     * and response objects will remain <i>locked in</i> on the returned
     * AsyncContext.
     *
     * @param servletRequest the ServletRequest used to initialize the
     * AsyncContext
     * @param servletResponse the ServletResponse used to initialize the
     * AsyncContext
     *
     * @return the (re)initialized AsyncContext
     * 
     * @throws IllegalStateException if this request is within the scope of
     * a filter or servlet that does not support asynchronous operations
     * (that is, {@link #isAsyncSupported} returns false),
     * or if this method is called again without any asynchronous dispatch
     * (resulting from one of the {@link AsyncContext#dispatch} methods),
     * is called outside the scope of any such dispatch, or is called again
     * within the scope of the same dispatch, or if the response has
     * already been closed
     *
     * @since Servlet 3.0
     */
    default public AsyncContext startAsync(ServletRequest servletRequest, ServletResponse servletResponse) throws IllegalStateException { return null; }
   
    /**
     * Checks if this request has been put into asynchronous mode.
     *
     * <p>A ServletRequest is put into asynchronous mode by calling
     * {@link #startAsync} or
     * {@link #startAsync(ServletRequest,ServletResponse)} on it.
     * 
     * <p>This method returns <tt>false</tt> if this request was
     * put into asynchronous mode, but has since been dispatched using
     * one of the {@link AsyncContext#dispatch} methods or released
     * from asynchronous mode via a call to {@link AsyncContext#complete}.
     *
     * @return true if this request has been put into asynchronous mode,
     * false otherwise
     *
     * @since Servlet 3.0
     */
    default public boolean isAsyncStarted() { return false; }

    /**
     * Checks if this request supports asynchronous operation.
     *
     * <p>Asynchronous operation is disabled for this request if this request
     * is within the scope of a filter or servlet that has not been annotated
     * or flagged in the deployment descriptor as being able to support
     * asynchronous handling.
     *
     * @return true if this request supports asynchronous operation, false
     * otherwise
     *
     * @since Servlet 3.0
     */
    default public boolean isAsyncSupported() { return false; }

    /**
     * Gets the AsyncContext that was created or reinitialized by the
     * most recent invocation of {@link #startAsync} or
     * {@link #startAsync(ServletRequest,ServletResponse)} on this request.
     *
     * @return the AsyncContext that was created or reinitialized by the
     * most recent invocation of {@link #startAsync} or
     * {@link #startAsync(ServletRequest,ServletResponse)} on
     * this request 
     *
     * @throws IllegalStateException if this request has not been put 
     * into asynchronous mode, i.e., if neither {@link #startAsync} nor
     * {@link #startAsync(ServletRequest,ServletResponse)} has been called
     *
     * @since Servlet 3.0
     */
    default public AsyncContext getAsyncContext() { return null; }

    /**
     * Gets the dispatcher type of this request.
     *
     * <p>The dispatcher type of a request is used by the container
     * to select the filters that need to be applied to the request:
     * Only filters with matching dispatcher type and url patterns will
     * be applied.
     * 
     * <p>Allowing a filter that has been configured for multiple 
     * dispatcher types to query a request for its dispatcher type
     * allows the filter to process the request differently depending on
     * its dispatcher type.
     *
     * <p>The initial dispatcher type of a request is defined as
     * <code>DispatcherType.REQUEST</code>. The dispatcher type of a request
     * dispatched via {@link RequestDispatcher#forward(ServletRequest,
     * ServletResponse)} or {@link RequestDispatcher#include(ServletRequest,
     * ServletResponse)} is given as <code>DispatcherType.FORWARD</code> or
     * <code>DispatcherType.INCLUDE</code>, respectively, while the
     * dispatcher type of an asynchronous request dispatched via
     * one of the {@link AsyncContext#dispatch} methods is given as
     * <code>DispatcherType.ASYNC</code>. Finally, the dispatcher type of a
     * request dispatched to an error page by the container's error handling
     * mechanism is given as <code>DispatcherType.ERROR</code>.
     *
     * @return the dispatcher type of this request
     * 
     * @see DispatcherType
     *
     * @since Servlet 3.0
     */
    default public DispatcherType getDispatcherType() { return null; }

}