timedalarm.java

来自「反向的AJAX。最大的特性是我们成为反向的Ajax。DWR1.x允许你用java」· Java 代码 · 共 103 行

/*
 * 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.dwrp;

import java.util.TimerTask;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.directwebremoting.util.StaticTimer;

/**
 * An Alarm that goes off after a certain length of time.
 * @author Joe Walker [joe at getahead dot ltd dot uk]
 */
public class TimedAlarm extends BasicAlarm implements Alarm
{
    /**
     * @param waitTime How long we wait before the Alarm goes off
     */
    public TimedAlarm(long waitTime)
    {
        this.waitTime = waitTime;
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.dwrp.PollHandler.Alarm#cancel()
     */
    public void cancel()
    {
        if (task != null)
        {
            task.cancel();
        }

        super.cancel();
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.dwrp.PollHandler.Alarm#setAlarmAction(org.directwebremoting.dwrp.PollHandler.Sleeper)
     */
    public void setAlarmAction(Sleeper sleeper)
    {
        if (task != null)
        {
            throw new IllegalStateException("An alarm action has already been set.");
        }

        super.setAlarmAction(sleeper);

        if (waitTime == 0)
        {
            raiseAlarm();
        }
        else
        {
            task = new TimerTask()
            {
                public void run()
                {
                    try
                    {
                        raiseAlarm();
                    }
                    catch (Exception ex)
                    {
                        log.warn("Unexpected error raising alarm", ex);
                    }
                }
            };
    
            StaticTimer.schedule(task, waitTime);
        }
    }

    /**
     * The task that causes the alarm to go off
     */
    private TimerTask task;

    /**
     * How long do we wait for?
     */
    protected long waitTime;

    /**
     * The log stream
     */
    protected static final Log log = LogFactory.getLog(TimedAlarm.class);
}