绝对全网首发，利用Disruptor EventHandler实现在多线程下顺序执行任务

disruptor有两种任务处理器，一个是EventHandler ,另一个是WorkHandler.
EventHandler可以彼此独立消费同一个队列中的任务，WorkHandler可以共同竞争消费同一个队列中的任务。也就是说，假设任务队列中有a、b、c、d三个事件，eventHandler1 和eventHandler2，这两个处理器都会去这4个事件，也就是每个事件会被处理两次，每个处理器处理一次；而如果有workHandler 和workHandler2这两个处理器，那么每个任务只会被其中一个处理器处理，这两处理器的处理时间总数加起来是这4个事件。
了解了这些，就可以能理解使用EventHandler为啥能实现多线程顺序处理了。
可以给事件定义一个hash函数，根据哈希取余的槽位下标和当前处理器的下标比较，判断出此事件是否应被当前的处理器处理，不该其处理的事件直接pass，避免重复消费

定义的哈希函数接口和统一的基础父类

public interface Hashed<K> {/*** 哈希码计算所需key** @return key值*/K getKey();/*** 计算哈希码** <p>*     默认实现是使用{@link  java.util.HashMap HashMap}的哈希计算公式</br>*     建议对此计算做个缓存，进一步提高性能* </p>** @param key 哈希码生成的输入key,此入参是{@link #getKey()}方法的返回值* @return 哈希码* @see #getKey()*/default int hash(K key) {if (key == null) {throw new NullPointerException("key must not be null");}int h;return (h = key.hashCode()) ^ (h >>> 16);}}public abstract class PartitionEventHandler<E extends Hashed<K>, K> implements EventHandler<E>, Cloneable {protected final Logger log = LoggerFactory.getLogger(getClass());private final static int NO_INIT_VALUE = -1;private int index;private int indexMask;public final int getIndex() {return index;}public final int getIndexMask() {return indexMask;}@Overridepublic final void onEvent(E event, long sequence, boolean endOfBatch) throws Exception {if (index == NO_INIT_VALUE || indexMask == NO_INIT_VALUE) {throw new IllegalStateException("this should be inited");}int position = event.hash(event.getKey()) & indexMask;if (index != position) {if (log.isTraceEnabled()) {log.trace("The event with key [{}] should be handled on slot [{}],but current slot is [{}], it will be ignored.",event.getKey(), position, index);}return;}if (log.isDebugEnabled()) {log.debug("The event with key [{}] is being handled on slot [{}].", event.getKey(), position);}doOnEvent(event, sequence, endOfBatch);}protected abstract void doOnEvent(E event, long sequence, boolean endOfBatch) throws Exception;@SafeVarargspublic static <E extends Hashed<K>, K> PartitionEventHandler<E, K>[] initHandlers(final PartitionEventHandler<E, K>... handlers) {if (handlers == null) {throw new NullPointerException("handlers must not be null");}if (handlers.length == 0) {throw new IllegalArgumentException("handlers length must be more than zero");}if (Integer.bitCount(handlers.length) != 1) {throw new IllegalArgumentException("handlers count must be a power of 2");}int indexMask = handlers.length - 1;for (int i = 0; i < handlers.length; i++) {PartitionEventHandler<E, K> handler = handlers[i];handler.indexMask = indexMask;handler.index = i;}return handlers;}@Overridepublic PartitionEventHandler<E, K> clone() {try {@SuppressWarnings("unchecked")PartitionEventHandler<E, K> handler = (PartitionEventHandler<E, K>) super.clone();handler.index = NO_INIT_VALUE;handler.indexMask = NO_INIT_VALUE;return handler;} catch (CloneNotSupportedException e) {//never occurthrow new RuntimeException("can not clone " + getClass(), e);}}public PartitionEventHandler<E, K>[] clones(int count) {if (count < 0) {throw new IllegalArgumentException("count must be more then zero");}@SuppressWarnings("unchecked")PartitionEventHandler<E, K>[] result = new PartitionEventHandler[count];for (int i = 0; i < count; i++) {result[i] = clone();}return result;}
}

测试代码

public class DisruptorTest05 {@Testpublic void test1() {CustomizableThreadFactory threadFactory = new CustomizableThreadFactory("event-handler-");threadFactory.setDaemon(false);Disruptor<ChatGroupEvent> disruptor = new Disruptor<>(new ChatGroupEventFactory(), 1024, threadFactory);ChatGroupEventHandler handler = new ChatGroupEventHandler();PartitionEventHandler<ChatGroupEvent, String>[] handlers = handler.clones(8);disruptor.handleEventsWith(PartitionEventHandler.initHandlers(handlers));disruptor.start();RingBuffer<ChatGroupEvent> ringBuffer = disruptor.getRingBuffer();Random rdm = new Random();long start = System.currentTimeMillis();for (int i = 0; i < 1000; i++) {long seq = ringBuffer.next();ChatGroupEvent chatGroupEvent = ringBuffer.get(seq);int rdmInt = rdm.nextInt(12);chatGroupEvent.setGroupId(String.format("groupId-%02d", rdmInt));chatGroupEvent.setGroupOwner(String.format("owner-%03d", i));String type = i % 2 == 0 ? "add" : "exit";chatGroupEvent.setChangeType(type);ringBuffer.publish(seq);}disruptor.shutdown();long spent = System.currentTimeMillis() - start;System.out.println("total time " + spent);System.out.println();}static class ChatGroupEventFactory implements EventFactory<ChatGroupEvent> {@Overridepublic ChatGroupEvent newInstance() {return new ChatGroupEvent();}}static class ChatGroupEventHandler extends PartitionEventHandler<ChatGroupEvent, String> {@Overrideprotected void doOnEvent(ChatGroupEvent event, long sequence, boolean endOfBatch) throws Exception {Thread.sleep(50);log.info("event key={},owner={},changeType={}, index={}", event.getKey(), event.getGroupOwner(), event.getChangeType(), getIndex());}}static class ChatGroupEvent implements Hashed<String> {private volatile  int hashcode=-1;private String groupId;private String changeType;private String groupOwner;@Overridepublic String getKey() {return groupId;}@Overridepublic int hash(String key) {if (hashcode == -1) {synchronized (this){if (hashcode == -1) {int h;hashcode = (h = key.hashCode()) ^ (h >>> 16);return hashcode;}}}return hashcode;}public String getGroupId() {return groupId;}public void setGroupId(String groupId) {this.groupId = groupId;}public String getChangeType() {return changeType;}public void setChangeType(String changeType) {this.changeType = changeType;}public String getGroupOwner() {return groupOwner;}public void setGroupOwner(String groupOwner) {this.groupOwner = groupOwner;}}
}