org.directwebremoting.server.servlet3.Servlet30Sleeper 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.servlet3;

import java.io.IOException;

import javax.servlet.AsyncContext;
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;

/**
 * A Sleeper that works with Servlet 3.0 async servlets.
 * @author Mike Wilson
 */
public class Servlet30Sleeper extends BaseSleeper
{
    /**
     * @throws IOException
     */
    public Servlet30Sleeper(HttpServletRequest request, HttpServletResponse response, RealScriptSession scriptSession, ScriptConduit conduit) throws IOException
    {
        super(response, scriptSession, conduit);
        this.request = request;
        this.response = response;

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

    /* (non-Javadoc)
     * @see org.directwebremoting.impl.BaseSleeper#enterSleep()
     */
    @Override
    protected void enterSleep()
    {
        asyncCtx = request.startAsync(request, response);
        asyncCtx.setTimeout(-1);

        synchronized (workLock)
        {
            if (queuedWork) {
                asyncCtx.start(new Runnable() {
                    public void run() {
                        resumeWork();
                    }
                });
            } 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 {
                asyncCtx.start(new Runnable() {
                    public void run() {
                        resumeWork();
                    }
                });
                workInProgress = true;
            }
        }
    }

    /**
     * The method that should be called by a background thread when we are being awakened
     */
    private void resumeWork()
    {
        while(true) {
            doWork();
            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
                    workInProgress = false;
                    return;
                }
            }
        }
    }

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

    // Set at construction
    private final HttpServletRequest request;
    private final HttpServletResponse response;

    // Internal state
    private AsyncContext asyncCtx = null;
    private final Object workLock = new Object();
    private boolean workInProgress = false;
    private boolean queuedWork = false;
}