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 boilerplate code between the web browser and your Java code. This version 4.0.2 works with Jakarta Servlet 4.0.2.

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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
{
    /** @param request ...
     * @param response ...
     * @param scriptSession ...
     * @param conduit ...
     * @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
    }

    @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;
        }
    }

    @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;
                }
            }
        }
    }

    @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;
}