面临问题
在游戏中我们经常会遇到定时器,例如从大方面来每日的零点,节假日双倍经验,boss刷新,从小方面来说回合制中该回合在多长时间内结束,战斗中buff/debuff状态时间,技能的cd时间等等都涉及到定时器,前一种我们实现方式比较多,例如最常用的crontab,quartz都可以实现,而后者更像一种闹钟,到时候就去唤醒一个事件.我们今天就先讨论了下后面这种”闹钟”如何实现.
设计实现
要使用闹钟我们首先想到的就是Timer,但在java 1.5后全新推出了ScheduledThreadPoolExecutor,我们用它来对Timer进行替代,其次我们需要定义一个间隔周期,让这个定时器每隔多长时间去跑一下,看看有没有什么任务可以执行,这个间隔不能太长,太长会导致某些任务触发不及时,但也不能太短,太短容易加重系统开销,我们暂定50毫秒走一次定时器,伪代码看起来像这样
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public class AlarmClock { private final static Logger LOG = LoggerFactory.getLogger(AlarmClock.class); // 默认间隔50ms private final static int INTERVAL = 50; private static AlarmClock clock; private volatile boolean active = false; private ScheduledThreadPoolExecutor executor; private AlarmClock() { executor = new ScheduledThreadPoolExecutor(DEFAULT_THREADS); } public synchronized static AlarmClock getInstance() { if (clock == null) { clock = new AlarmClock(); } return clock; } public void start() { if (active) { return; } active = true; executor.scheduleWithFixedDelay(new ScheduledTask(), 0, INTERVAL, TimeUnit.MILLISECONDS); } // 定时任务 class ScheduledTask implements Runnable { @Override public void run() { // TODO 需要触发的任务 } } } |
有了AlarmClock后,我们自然需要定义ScheduledTask中需要触发的方法,那这里我们就需要统一的Alarm事件接口,这里我们为简单使用就直接设计了AlarmEvent,代码就改成这样
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public class AlarmClock { private final static Logger LOG = LoggerFactory.getLogger(AlarmClock.class); // 默认间隔50ms private final static int INTERVAL = 50; private static AlarmClock clock; private volatile boolean active = false; private CopyOnWriteArrayList<AlarmEvent> list; private ScheduledThreadPoolExecutor executor; private AlarmClock() { list = new CopyOnWriteArrayList<AlarmEvent>(); executor = new ScheduledThreadPoolExecutor(DEFAULT_THREADS); } public synchronized static AlarmClock getInstance() { if (clock == null) { clock = new AlarmClock(); } return clock; } public void start() { if (active) { return; } active = true; executor.scheduleWithFixedDelay(new ScheduledTask(), 0, INTERVAL, TimeUnit.MILLISECONDS); } public void fire(long currentTime) { for (AlarmEvent alarmEvent : list) { // 判断任务是否已经完成 if (alarmEvent.getCount() == 0) { list.remove(alarmEvent); } else if (currentTime >= alarmEvent.getNextTime()) { // 判断任务时间是否已到 alarmEvent.fire(currentTime); } } } public void addEvent(AlarmEvent event) { list.add(event); } public void removeEvent(AlarmEvent event) { list.remove(event); } // 定时任务 class ScheduledTask implements Runnable { @Override public void run() { try { fire(System.currentTimeMillis()); } catch (Exception e) { LOG.error("alarm clock fire error", e); } } } } |
根据上面AlarmEvent的操作,我们可以进行如下扩展,例如增加AlarmListener接口,用来实现onTime方法,同时我们还可以增加parameter属性这样AlarmEvent就能完成很多不同的任务.
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public class AlarmEvent { private final static Logger LOG = LoggerFactory.getLogger(AlarmEvent.class); private AlarmListener listener = null; private Object parameter = null; private int intervalTime = 0; private int count = 0; private int initTime = 0; private long currentTime = 0L; private long startTime = 0L; private long nextTime = 0L; private boolean absolute = false; /** * 构造方法 * * @param listener 侦听 * @param parameter 参数 * @param intervalTime 间隔时间 */ public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime) { this(listener, parameter, intervalTime, -1, 0, false); } /** * 构造方法 * * @param listener 侦听 * @param parameter 参数 * @param intervalTime 间隔时间 * @param absolute 是否是绝对时间 */ public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, boolean absolute) { this(listener, parameter, intervalTime, -1, 0, absolute); } /** * 构造方法 * * @param listener 侦听 * @param parameter 参数 * @param intervalTime 间隔时间 * @param count 执行次数 */ public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, int count) { this(listener, parameter, intervalTime, count, 0, false); } /** * 构造方法 * * @param listener 侦听 * @param parameter 参数 * @param intervalTime 间隔时间 * @param count 执行次数 * @param absolute 是否是绝对时间 */ public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, int count, boolean absolute) { this(listener, parameter, intervalTime, count, 0, absolute); } /** * 构造方法 * * @param listener 侦听 * @param parameter 参数 * @param intervalTime 间隔时间 * @param count 执行次数 * @param initTime 初始时间后执行 */ public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, int count, int initTime) { this(listener, parameter, intervalTime, count, initTime, false); } public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, int count, int initTime, long startTime) { this(listener, parameter, intervalTime, count, initTime, startTime, false); } public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, int count, int initTime, boolean absolute) { if (listener == null) { throw new IllegalArgumentException(getClass().getName() + " listener is null"); } this.listener = listener; if (parameter == null) { throw new IllegalArgumentException(getClass().getName() + " parameter is null"); } this.parameter = parameter; this.intervalTime = intervalTime; this.count = count; this.initTime = initTime; this.absolute = absolute; this.startTime = System.currentTimeMillis(); this.nextTime = (this.startTime + initTime); } public AlarmEvent(AlarmListener listener, Object parameter, int intervalTime, int count, int initTime, long startTime, boolean absolute) { if (listener == null) { throw new IllegalArgumentException(getClass().getName() + " listener is null"); } this.listener = listener; if (parameter == null) { throw new IllegalArgumentException(getClass().getName() + " parameter is null"); } this.parameter = parameter; this.intervalTime = intervalTime; this.count = count; this.initTime = initTime; this.absolute = absolute; if (startTime == 0) { this.startTime = System.currentTimeMillis(); } else { this.startTime = startTime; } this.nextTime = (this.startTime + initTime); } public void fire(long currentTime) { this.count -= 1; this.currentTime = currentTime; try { listener.onTimer(this); } catch (Throwable e) { LOG.error("process alarm event error!", e); } this.nextTime = (absolute ? nextTime + intervalTime : currentTime + intervalTime); } // setter getter toString... } |
基本上这定时器就已经实现完毕了,基本上这个闹钟已经能完成很多工作,如果还有特殊需要可以自行扩展AlarmEvent,下面我们来看一个最简单的例子
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@Service public class AppListener implements AlarmListener { private final static Logger LOG = LoggerFactory.getLogger(AppListener.class); @Override public void onTimer(AlarmEvent alarmEvent) { LOG.debug("event:{}", alarmEvent); } } |
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@Service public class AppService { private final static Logger LOG = LoggerFactory.getLogger(AppService .class); @Autowired private AppListener appListener; public void doit() { AlarmClock.getInstance().start(); // 每10秒触发一次 参数是abc AlarmEvent event = new AlarmEvent(appListener, "abc", 10000); AlarmClock.getInstance().addEvent(event); } } |