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//  Copyright (c) 1995-2019 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
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//  You may elect to redistribute this code under either of these licenses.
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package org.eclipse.jetty.server.handler;

import java.io.IOException;
import javax.servlet.AsyncContext;
import javax.servlet.DispatcherType;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.Request;

A handler wrapper that provides the framework to asynchronously
delay the handling of a request.  While it uses standard servlet
API for asynchronous servlets, it adjusts the dispatch type of the
request so that it does not appear to be asynchronous during the
delayed dispatch.
/**
 * A handler wrapper that provides the framework to asynchronously
 * delay the handling of a request.  While it uses standard servlet
 * API for asynchronous servlets, it adjusts the dispatch type of the
 * request so that it does not appear to be asynchronous during the
 * delayed dispatch.
 */
public class AsyncDelayHandler extends HandlerWrapper
{
    public static final String AHW_ATTR = "o.e.j.s.h.AsyncHandlerWrapper";

    @Override
    public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        if (!isStarted() || _handler == null)
            return;

        // Get the dispatcher types
        DispatcherType ctype = baseRequest.getDispatcherType();
        DispatcherType dtype = (DispatcherType)baseRequest.getAttribute(AHW_ATTR);
        Object asyncContextPath = null;
        Object asyncPathInfo = null;
        Object asyncQueryString = null;
        Object asyncRequestUri = null;
        Object asyncServletPath = null;

        // Is this request a restarted one?
        boolean restart = false;
        if (dtype != null)
        {
            // fake the dispatch type to the original
            baseRequest.setAttribute(AHW_ATTR, null);
            baseRequest.setDispatcherType(dtype);
            restart = true;

            asyncContextPath = baseRequest.getAttribute(AsyncContext.ASYNC_CONTEXT_PATH);
            baseRequest.setAttribute(AsyncContext.ASYNC_CONTEXT_PATH, null);
            asyncPathInfo = baseRequest.getAttribute(AsyncContext.ASYNC_PATH_INFO);
            baseRequest.setAttribute(AsyncContext.ASYNC_PATH_INFO, null);
            asyncQueryString = baseRequest.getAttribute(AsyncContext.ASYNC_QUERY_STRING);
            baseRequest.setAttribute(AsyncContext.ASYNC_QUERY_STRING, null);
            asyncRequestUri = baseRequest.getAttribute(AsyncContext.ASYNC_REQUEST_URI);
            baseRequest.setAttribute(AsyncContext.ASYNC_REQUEST_URI, null);
            asyncServletPath = baseRequest.getAttribute(AsyncContext.ASYNC_SERVLET_PATH);
            baseRequest.setAttribute(AsyncContext.ASYNC_SERVLET_PATH, null);
        }

        // Should we handle this request now?
        if (!startHandling(baseRequest, restart))
        {
            // No, so go async and remember dispatch type
            AsyncContext context = baseRequest.startAsync();
            baseRequest.setAttribute(AHW_ATTR, ctype);

            delayHandling(baseRequest, context);
            return;
        }

        // Handle the request
        try
        {
            _handler.handle(target, baseRequest, request, response);
        }
        finally
        {
            if (restart)
            {
                // reset the request
                baseRequest.setDispatcherType(ctype);
                baseRequest.setAttribute(AsyncContext.ASYNC_CONTEXT_PATH, asyncContextPath);
                baseRequest.setAttribute(AsyncContext.ASYNC_PATH_INFO, asyncPathInfo);
                baseRequest.setAttribute(AsyncContext.ASYNC_QUERY_STRING, asyncQueryString);
                baseRequest.setAttribute(AsyncContext.ASYNC_REQUEST_URI, asyncRequestUri);
                baseRequest.setAttribute(AsyncContext.ASYNC_SERVLET_PATH, asyncServletPath);
            }

            // signal the request is leaving the handler
            endHandling(baseRequest);
        }
    }

    
Called to indicate that a request has been presented for handling
Params:
request – The request to handle
restart – True if this request is being restarted after a delay
Returns:
True if the request should be handled now/**
     * Called to indicate that a request has been presented for handling
     *
     * @param request The request to handle
     * @param restart True if this request is being restarted after a delay
     * @return True if the request should be handled now
     */
    protected boolean startHandling(Request request, boolean restart)
    {
        return true;
    }

    
Called to indicate that a requests handling is being delayed/
The implementation should arrange for context.dispatch() to be
called when the request should be handled.  It may also set
timeouts on the context.
Params:
request – The request to be delayed
context – The AsyncContext of the delayed request/**
     * Called to indicate that a requests handling is being delayed/
     * The implementation should arrange for context.dispatch() to be
     * called when the request should be handled.  It may also set
     * timeouts on the context.
     *
     * @param request The request to be delayed
     * @param context The AsyncContext of the delayed request
     */
    protected void delayHandling(Request request, AsyncContext context)
    {
        context.dispatch();
    }

    
Called to indicated the handling of the request is ending.
This is only the end of the current dispatch of the request and
if the request is asynchronous, it may be handled again.
Params:
request – The request/**
     * Called to indicated the handling of the request is ending.
     * This is only the end of the current dispatch of the request and
     * if the request is asynchronous, it may be handled again.
     *
     * @param request The request
     */
    protected void endHandling(Request request)
    {

    }
}