javax.servlet.AsyncContext Maven / Gradle / Ivy
/*
* Copyright (c) 2017, 2018 Oracle and/or its affiliates and others.
* All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package javax.servlet;
/**
* Class representing the execution context for an asynchronous operation that was initiated on a ServletRequest.
*
*
* An AsyncContext is created and initialized by a call to {@link ServletRequest#startAsync()} or
* {@link ServletRequest#startAsync(ServletRequest, ServletResponse)}. Repeated invocations of these methods will return
* the same AsyncContext instance, reinitialized as appropriate.
*
*
* In the event that an asynchronous operation has timed out, the container must run through these steps:
*
* - Invoke, at their {@link AsyncListener#onTimeout onTimeout} method, all {@link AsyncListener} instances registered
* with the ServletRequest on which the asynchronous operation was initiated.
* - If none of the listeners called {@link #complete} or any of the {@link #dispatch} methods, perform an error
* dispatch with a status code equal to HttpServletResponse.SC_INTERNAL_SERVER_ERROR.
* - If no matching error page was found, or the error page did not call {@link #complete} or any of the
* {@link #dispatch} methods, call {@link #complete}.
*
*
* @since Servlet 3.0
*/
public interface AsyncContext {
/**
* The name of the request attribute under which the original request URI is made available to the target of a
* {@link #dispatch(String)} or {@link #dispatch(ServletContext,String)}
*/
static final String ASYNC_REQUEST_URI = "javax.servlet.async.request_uri";
/**
* The name of the request attribute under which the original context path is made available to the target of a
* {@link #dispatch(String)} or {@link #dispatch(ServletContext,String)}
*/
static final String ASYNC_CONTEXT_PATH = "javax.servlet.async.context_path";
/**
* The name of the request attribute under which the original {@link javax.servlet.http.HttpServletMapping} is made
* available to the target of a {@link #dispatch(String)} or {@link #dispatch(ServletContext,String)}
*/
static final String ASYNC_MAPPING = "javax.servlet.async.mapping";
/**
* The name of the request attribute under which the original path info is made available to the target of a
* {@link #dispatch(String)} or {@link #dispatch(ServletContext,String)}
*/
static final String ASYNC_PATH_INFO = "javax.servlet.async.path_info";
/**
* The name of the request attribute under which the original servlet path is made available to the target of a
* {@link #dispatch(String)} or {@link #dispatch(ServletContext,String)}
*/
static final String ASYNC_SERVLET_PATH = "javax.servlet.async.servlet_path";
/**
* The name of the request attribute under which the original query string is made available to the target of a
* {@link #dispatch(String)} or {@link #dispatch(ServletContext,String)}
*/
static final String ASYNC_QUERY_STRING = "javax.servlet.async.query_string";
/**
* Gets the request that was used to initialize this AsyncContext by calling {@link ServletRequest#startAsync()} or
* {@link ServletRequest#startAsync(ServletRequest, ServletResponse)}.
*
* @return the request that was used to initialize this AsyncContext
*
* @exception IllegalStateException if {@link #complete} or any of the {@link #dispatch} methods has been called in
* the asynchronous cycle
*/
public ServletRequest getRequest();
/**
* Gets the response that was used to initialize this AsyncContext by calling {@link ServletRequest#startAsync()} or
* {@link ServletRequest#startAsync(ServletRequest, ServletResponse)}.
*
* @return the response that was used to initialize this AsyncContext
*
* @exception IllegalStateException if {@link #complete} or any of the {@link #dispatch} methods has been called in
* the asynchronous cycle
*/
public ServletResponse getResponse();
/**
* Checks if this AsyncContext was initialized with the original or application-wrapped request and response
* objects.
*
*
* This information may be used by filters invoked in the outbound direction, after a request was put into
* asynchronous mode, to determine whether any request and/or response wrappers that they added during their
* inbound invocation need to be preserved for the duration of the asynchronous operation, or may be
* released.
*
* @return true if this AsyncContext was initialized with the original request and response objects by calling
* {@link ServletRequest#startAsync()}, or if it was initialized by calling
* {@link ServletRequest#startAsync(ServletRequest, ServletResponse)}, and neither the ServletRequest nor
* ServletResponse arguments carried any application-provided wrappers; false otherwise
*/
public boolean hasOriginalRequestAndResponse();
/**
* Dispatches the request and response objects of this AsyncContext to the servlet container.
*
*
* If the asynchronous cycle was started with {@link ServletRequest#startAsync(ServletRequest, ServletResponse)},
* and the request passed is an instance of HttpServletRequest, then the dispatch is to the URI returned by
* {@link javax.servlet.http.HttpServletRequest#getRequestURI}. Otherwise, the dispatch is to the URI of the request
* when it was last dispatched by the container.
*
*
* The following sequence illustrates how this will work:
*
*
* {@code
* // REQUEST dispatch to /url/A
* AsyncContext ac = request.startAsync();
* ...
* ac.dispatch(); // ASYNC dispatch to /url/A
*
* // REQUEST to /url/A
* // FORWARD dispatch to /url/B
* request.getRequestDispatcher("/url/B").forward(request,response);
* // Start async operation from within the target of the FORWARD
* // dispatch
* ac = request.startAsync();
* ...
* ac.dispatch(); // ASYNC dispatch to /url/A
*
* // REQUEST to /url/A
* // FORWARD dispatch to /url/B
* request.getRequestDispatcher("/url/B").forward(request,response);
* // Start async operation from within the target of the FORWARD
* // dispatch
* ac = request.startAsync(request,response);
* ...
* ac.dispatch(); // ASYNC dispatch to /url/B
* }
*
*
*
* This method returns immediately after passing the request and response objects to a container managed thread, on
* which the dispatch operation will be performed. If this method is called before the container-initiated dispatch
* that called startAsync has returned to the container, the dispatch operation will be delayed until after
* the container-initiated dispatch has returned to the container.
*
*
* The dispatcher type of the request is set to DispatcherType.ASYNC. Unlike
* {@link RequestDispatcher#forward(ServletRequest, ServletResponse) forward dispatches}, the response buffer and
* headers will not be reset, and it is legal to dispatch even if the response has already been committed.
*
*
* Control over the request and response is delegated to the dispatch target, and the response will be closed when
* the dispatch target has completed execution, unless {@link ServletRequest#startAsync()} or
* {@link ServletRequest#startAsync(ServletRequest, ServletResponse)} are called.
*
*
* Any errors or exceptions that may occur during the execution of this method must be caught and handled by the
* container, as follows:
*
* - Invoke, at their {@link AsyncListener#onError onError} method, all {@link AsyncListener} instances registered
* with the ServletRequest for which this AsyncContext was created, and make the caught Throwable available
* via {@link AsyncEvent#getThrowable}.
* - If none of the listeners called {@link #complete} or any of the {@link #dispatch} methods, perform an error
* dispatch with a status code equal to HttpServletResponse.SC_INTERNAL_SERVER_ERROR, and make the above
* Throwable available as the value of the RequestDispatcher.ERROR_EXCEPTION request
* attribute.
* - If no matching error page was found, or the error page did not call {@link #complete} or any of the
* {@link #dispatch} methods, call {@link #complete}.
*
*
*
* There can be at most one asynchronous dispatch operation per asynchronous cycle, which is started by a call to
* one of the {@link ServletRequest#startAsync} methods. Any attempt to perform an additional asynchronous dispatch
* operation within the same asynchronous cycle will result in an IllegalStateException. If startAsync is
* subsequently called on the dispatched request, then any of the dispatch or {@link #complete} methods may be
* called.
*
* @throws IllegalStateException if one of the dispatch methods has been called and the startAsync method has not
* been called during the resulting dispatch, or if {@link #complete} was called
*
* @see ServletRequest#getDispatcherType
*/
public void dispatch();
/**
* Dispatches the request and response objects of this AsyncContext to the given path.
*
*
* The path parameter is interpreted in the same way as in
* {@link ServletRequest#getRequestDispatcher(String)}, within the scope of the {@link ServletContext} from which
* this AsyncContext was initialized.
*
*
* All path related query methods of the request must reflect the dispatch target, while the original request URI,
* context path, path info, servlet path, and query string may be recovered from the {@link #ASYNC_REQUEST_URI},
* {@link #ASYNC_CONTEXT_PATH}, {@link #ASYNC_PATH_INFO}, {@link #ASYNC_SERVLET_PATH}, and
* {@link #ASYNC_QUERY_STRING} attributes of the request. These attributes will always reflect the original path
* elements, even under repeated dispatches.
*
*
* There can be at most one asynchronous dispatch operation per asynchronous cycle, which is started by a call to
* one of the {@link ServletRequest#startAsync} methods. Any attempt to perform an additional asynchronous dispatch
* operation within the same asynchronous cycle will result in an IllegalStateException. If startAsync is
* subsequently called on the dispatched request, then any of the dispatch or {@link #complete} methods may be
* called.
*
*
* See {@link #dispatch()} for additional details, including error handling.
*
* @param path the path of the dispatch target, scoped to the ServletContext from which this AsyncContext was
* initialized
*
* @throws IllegalStateException if one of the dispatch methods has been called and the startAsync method has not
* been called during the resulting dispatch, or if {@link #complete} was called
*
* @see ServletRequest#getDispatcherType
*/
public void dispatch(String path);
/**
* Dispatches the request and response objects of this AsyncContext to the given path scoped to the given
* context.
*
*
* The path parameter is interpreted in the same way as in
* {@link ServletRequest#getRequestDispatcher(String)}, except that it is scoped to the given context.
*
*
* All path related query methods of the request must reflect the dispatch target, while the original request URI,
* context path, path info, servlet path, and query string may be recovered from the {@link #ASYNC_REQUEST_URI},
* {@link #ASYNC_CONTEXT_PATH}, {@link #ASYNC_PATH_INFO}, {@link #ASYNC_SERVLET_PATH}, and
* {@link #ASYNC_QUERY_STRING} attributes of the request. These attributes will always reflect the original path
* elements, even under repeated dispatches.
*
*
* There can be at most one asynchronous dispatch operation per asynchronous cycle, which is started by a call to
* one of the {@link ServletRequest#startAsync} methods. Any attempt to perform an additional asynchronous dispatch
* operation within the same asynchronous cycle will result in an IllegalStateException. If startAsync is
* subsequently called on the dispatched request, then any of the dispatch or {@link #complete} methods may be
* called.
*
*
* See {@link #dispatch()} for additional details, including error handling.
*
* @param context the ServletContext of the dispatch target
* @param path the path of the dispatch target, scoped to the given ServletContext
*
* @throws IllegalStateException if one of the dispatch methods has been called and the startAsync method has not
* been called during the resulting dispatch, or if {@link #complete} was called
*
* @see ServletRequest#getDispatcherType
*/
public void dispatch(ServletContext context, String path);
/**
* Completes the asynchronous operation that was started on the request that was used to initialze this
* AsyncContext, closing the response that was used to initialize this AsyncContext.
*
*
* Any listeners of type {@link AsyncListener} that were registered with the ServletRequest for which this
* AsyncContext was created will be invoked at their {@link AsyncListener#onComplete(AsyncEvent) onComplete} method.
*
*
* It is legal to call this method any time after a call to {@link ServletRequest#startAsync()} or
* {@link ServletRequest#startAsync(ServletRequest, ServletResponse)}, and before a call to one of the
* dispatch methods of this class. If this method is called before the container-initiated dispatch that
* called startAsync has returned to the container, then the call will not take effect (and any invocations
* of {@link AsyncListener#onComplete(AsyncEvent)} will be delayed) until after the container-initiated dispatch has
* returned to the container.
*/
public void complete();
/**
* Causes the container to dispatch a thread, possibly from a managed thread pool, to run the specified
* Runnable. The container may propagate appropriate contextual information to the Runnable.
*
* @param run the asynchronous handler
*/
public void start(Runnable run);
/**
* Registers the given {@link AsyncListener} with the most recent asynchronous cycle that was started by a call to
* one of the {@link ServletRequest#startAsync} methods.
*
*
* The given AsyncListener will receive an {@link AsyncEvent} when the asynchronous cycle completes successfully,
* times out, results in an error, or a new asynchronous cycle is being initiated via one of the
* {@link ServletRequest#startAsync} methods.
*
*
* AsyncListener instances will be notified in the order in which they were added.
*
*
* If {@link ServletRequest#startAsync(ServletRequest, ServletResponse)} or {@link ServletRequest#startAsync} is
* called, the exact same request and response objects are available from the {@link AsyncEvent} when the
* {@link AsyncListener} is notified.
*
* @param listener the AsyncListener to be registered
*
* @throws IllegalStateException if this method is called after the container-initiated dispatch, during which one
* of the {@link ServletRequest#startAsync} methods was called, has returned to the
* container
*/
public void addListener(AsyncListener listener);
/**
* Registers the given {@link AsyncListener} with the most recent asynchronous cycle that was started by a call to
* one of the {@link ServletRequest#startAsync} methods.
*
*
* The given AsyncListener will receive an {@link AsyncEvent} when the asynchronous cycle completes successfully,
* times out, results in an error, or a new asynchronous cycle is being initiated via one of the
* {@link ServletRequest#startAsync} methods.
*
*
* AsyncListener instances will be notified in the order in which they were added.
*
*
* The given ServletRequest and ServletResponse objects will be made available to the given AsyncListener via the
* {@link AsyncEvent#getSuppliedRequest getSuppliedRequest} and {@link AsyncEvent#getSuppliedResponse
* getSuppliedResponse} methods, respectively, of the {@link AsyncEvent} delivered to it. These objects should not
* be read from or written to, respectively, at the time the AsyncEvent is delivered, because additional wrapping
* may have occurred since the given AsyncListener was registered, but may be used in order to release any resources
* associated with them.
*
* @param listener the AsyncListener to be registered
* @param servletRequest the ServletRequest that will be included in the AsyncEvent
* @param servletResponse the ServletResponse that will be included in the AsyncEvent
*
* @throws IllegalStateException if this method is called after the container-initiated dispatch, during which one
* of the {@link ServletRequest#startAsync} methods was called, has returned to the
* container
*/
public void addListener(AsyncListener listener, ServletRequest servletRequest, ServletResponse servletResponse);
/**
* Instantiates the given {@link AsyncListener} class.
*
*
* The returned AsyncListener instance may be further customized before it is registered with this AsyncContext via
* a call to one of the addListener methods.
*
*
* The given AsyncListener class must define a zero argument constructor, which is used to instantiate it.
*
*
* This method supports resource injection if the given clazz represents a Managed Bean. See the Jakarta EE
* platform and CDI specifications for additional details about Managed Beans and resource injection.
*
*
* This method supports any annotations applicable to AsyncListener.
*
* @param the class of the object to instantiate
* @param clazz the AsyncListener class to instantiate
*
* @return the new AsyncListener instance
*
* @throws ServletException if the given clazz fails to be instantiated
*/
public T createListener(Class clazz) throws ServletException;
/**
* Sets the timeout (in milliseconds) for this AsyncContext.
*
*
* The timeout applies to this AsyncContext once the container-initiated dispatch during which one of the
* {@link ServletRequest#startAsync} methods was called has returned to the container.
*
*
* The timeout will expire if neither the {@link #complete} method nor any of the dispatch methods are called. A
* timeout value of zero or less indicates no timeout.
*
*
* If {@link #setTimeout} is not called, then the container's default timeout, which is available via a call to
* {@link #getTimeout}, will apply.
*
*
* The default value is 30000 ms.
*
* @param timeout the timeout in milliseconds
*
* @throws IllegalStateException if this method is called after the container-initiated dispatch, during which one
* of the {@link ServletRequest#startAsync} methods was called, has returned to the
* container
*/
public void setTimeout(long timeout);
/**
* Gets the timeout (in milliseconds) for this AsyncContext.
*
*
* This method returns the container's default timeout for asynchronous operations, or the timeout value passed to
* the most recent invocation of {@link #setTimeout}.
*
*
* A timeout value of zero or less indicates no timeout.
*
* @return the timeout in milliseconds
*/
public long getTimeout();
}