下面2张图来自：http://www.open-open.com/doc/view/2e0a82e0081d489dace301a2c512053c
关于Zookeeper服务安装，配置，启动, 客户端操作参见：
http://aiilive.blog.51cto.com/1925756/1684451
http://aiilive.blog.51cto.com/1925756/1684145
1.利用Zookeeper的znode数据版本生成序列号
利用zkClient封装包操作实现：
//提前创建好存储Seq的"/createSeq"结点 CreateMode.PERSISTENT
public static final String SEQ_ZNODE = "/seq"//通过znode数据版本实现分布式seq生成
public static class Task1 implements Runnable {private final String taskName;public Task1(String taskName) {this.taskName = taskName;}@Overridepublic void run() {ZkClient zkClient = new ZkClient("192.168.88.153:2181", 3000, 1000);Stat stat = zkClient.writeData(SEQ_ZNODE, new byte[0], -1);int versionAsSeq = stat.getVersion();System.out.println(taskName + " obtain seq=" + versionAsSeq);zkClient.close();}
}//main
final ExecutorService service = Executors.newFixedThreadPool(20);for (int i = 0; i < 20; i++) {service.execute(new Task1("[Concurrent-" + i + "]"));
}2.利用临时带序列号的znode实现和分布式锁持久化znode实现
2.1 下图是利用分布式锁持久化znode实现
客户端采用apache curator 框架，代码：https://code.csdn.net/snippets/929300
2.2利用临时带序列号的znode实现
客户端采用：zkClient （https://github.com/adyliu/zkclient）
//提前创建好锁对象的结点"/lock" CreateMode.PERSISTENT
public static final String LOCK_ZNODE = "/lock";//分布式锁实现分布式seq生成
public static class Task2 implements Runnable, IZkChildListener {private final String taskName;private final ZkClient zkClient;private final String lockPrefix = "/loc";private final String selfZnode;public Task2(String taskName) {this.taskName = taskName;zkClient = new ZkClient("192.168.88.153:2181", 30000, 10000);selfZnode = zkClient.createEphemeralSequential(LOCK_ZNODE + lockPrefix, new byte[0]);}@Overridepublic void run() {zkClient.subscribeChildChanges(LOCK_ZNODE, this);do {} while (zkClient.isConnected());}private void createSeq() {Stat stat = new Stat();byte[] oldData = zkClient.readData(LOCK_ZNODE, stat);byte[] newData = update(oldData);zkClient.writeData(LOCK_ZNODE, newData);System.out.println(taskName + selfZnode + " obtain seq=" + new String(newData));}private byte[] update(byte[] currentData) {String s = new String(currentData);int d = Integer.parseInt(s);d = d + 1;s = String.valueOf(d);return s.getBytes();}@Overridepublic void handleChildChange(String parentPath, List<String> currentChildren) throws Exception {String[] childrensZnode = currentChildren.toArray(new String[currentChildren.size()]);Arrays.sort(childrensZnode);String minZnode = LOCK_ZNODE + "/" + childrensZnode[0];if (selfZnode.equals(minZnode)) {createSeq();zkClient.unsubscribeChildChanges(LOCK_ZNODE, this);zkClient.delete(selfZnode);zkClient.close();}}
}完整代码参见：https://code.csdn.net/snippets/929320
