org.directwebremoting.server.jetty.JettyContinuationSleeper Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2005 Joe Walker
 *
 * 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 org.directwebremoting.server.jetty;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.directwebremoting.extend.RealScriptSession;
import org.directwebremoting.extend.ScriptConduit;
import org.directwebremoting.impl.BaseSleeper;
import org.eclipse.jetty.continuation.Continuation;
import org.eclipse.jetty.continuation.ContinuationSupport;

/**
 * A Sleeper that works with Jetty Continuations
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 * @author Tim Peierls [tim at peierls dot net]
 * @author Mike Wilson
 */
public class JettyContinuationSleeper extends BaseSleeper
{
    /**
     * @param request The request into which we store this as an attribute
     * @param conduit
     * @param scriptSession
     * @param response
     * @throws IOException
     */
    public JettyContinuationSleeper(HttpServletRequest request, HttpServletResponse response, RealScriptSession scriptSession, ScriptConduit conduit) throws IOException
    {
        super(response, scriptSession, conduit);

        this.request = request;

        workInProgress = true; // block doing work until we officially enter sleep
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.impl.BaseSleeper#enterSleep()
     */
    @Override
    protected void enterSleep()
    {
        continuation = ContinuationSupport.getContinuation(request);
        continuation.setAttribute(ATTRIBUTE_SLEEPER, this);
        continuation.setTimeout(0);
        continuation.suspend();

        synchronized (workLock)
        {
            if (queuedWork) {
                continuation.resume(); // will eventually trigger resumeWork() from a container thread
            } else {
                workInProgress = false; // open up for doing new work
            }
            queuedWork = false;
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.impl.BaseSleeper#wakeUp()
     */
    @Override
    protected void wakeUp()
    {
        synchronized (workLock)
        {
            if (workInProgress) {
                queuedWork = true;
            } else {
                continuation.resume(); // will eventually trigger resumeWork() from a container thread
                workInProgress = true;
            }
        }
    }

    /**
     * The method that should be called by a background thread when we are being awakened
     */
    public void resumeWork()
    {
        while(true) {
            doWork();
            if (continuation.getAttribute(ATTRIBUTE_SLEEPER) == null) {
                // If we have disconnected the Sleeper from the container then it is time to end the async cycle
                return;
            }
            synchronized (workLock)
            {
                if (queuedWork) {
                    // New work has arrived so fall through to take another spin in the loop
                    queuedWork = false;
                } else {
                    // No work in the queue so exit loop and go to sleep again
                    continuation.suspend();
                    workInProgress = false;
                    return;
                }
            }
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.impl.BaseSleeper#close()
     */
    @Override
    protected void close()
    {
        if (continuation != null) {
            continuation.removeAttribute(ATTRIBUTE_SLEEPER);
        }
    }

    /**
     * Retrieve a stashed sleeper from a request.
     */
    public static JettyContinuationSleeper getSleeper(HttpServletRequest request)
    {
        return (JettyContinuationSleeper) request.getAttribute(ATTRIBUTE_SLEEPER);
    }

    // Set at construction
    private final HttpServletRequest request;

    // Internal state
    private Continuation continuation = null;
    private final Object workLock = new Object();
    private boolean workInProgress = false;
    private boolean queuedWork = false;

    /**
     * We remember the sleeper on a request attribute
     */
    protected static final String ATTRIBUTE_SLEEPER = JettyContinuationSleeper.class.getName();
}