zookeeper主备切换学习

//抄的，
public class AbstractZooKeeper implements Watcher {
	private static final int Session_TIME =2000;
	protected ZooKeeper zookeeper ;
	
	/*一个同步辅助类，在完成一组正在其他线程中执行的操作之前，
	它允许一个或多个线程一直等待。
	用给定的计数 初始化 CountDownLatch。
	由于调用了 countDown() 方法，
	所以在当前计数到达零之前，await 方法会一直受阻塞。
	之后，会释放所有等待的线程，await 的所有后续调用都将立即返回。
	这种现象只出现一次——计数无法被重置
	*/
	protected CountDownLatch countDownLatch = new CountDownLatch(1);
	
	public void connect(String hosts) throws IOException,InterruptedException{
		zookeeper= new ZooKeeper(hosts,Session_TIME,this);
		countDownLatch.await();
	}
	//监听
	public void process(WatchedEvent event) {
		
		/*	一旦客户端和服务器的某一个节点建立连接
		 * （注意，虽然集群有多个节点，
		 * 但是客户端一次连接到一个节点就行了），
		 * 并完成一次version、zxid的同步，
		 * 这时的客户端和服务器的连接状态就是SyncConnected*/
		if(event.getState() == KeeperState.SyncConnected){
			countDownLatch.countDown();
			System.out.println(countDownLatch.getCount());
		}
		
	}
	public void close() throws InterruptedException{
		zookeeper.close();
	}
	
}

///zookeeper的一些操作。和监听zookeeper临时节点删除事件。
public class ZookeeperService extends AbstractZooKeeper {

	private static final String host = "helloword1";
	//private static final String host = "helloword2";
	private static final String rootNode="/mynode";
	
	public void Create() throws KeeperException, InterruptedException, UnsupportedEncodingException {
		
		//EPHEMERAL :临时节点
		this.zookeeper.create(rootNode, host.getBytes("utf-8"), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

	}
	//判断存不存在时开始监听
	public Boolean Exist() throws KeeperException, InterruptedException {
		return (this.zookeeper.exists(rootNode, true) != null);
	}
	
	//监听事件
	@Override
	public void process(WatchedEvent event){
		if(event.getType() == EventType.NodeDeleted){
			try {
				this.Create();
				System.out.println(host);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} 
			System.out.println(host);
		}
		else{
			//由于第一次是阻塞的，
			//如果连接成功需要调用父类的将countDownLatch阻塞去掉
			super.process(event);
		}
		
	}
	public Boolean getChild(String path) throws KeeperException, InstantiationException {
		Boolean res = false;
		try {

			List<String> list = this.zookeeper.getChildren(path, false);
			if (list.isEmpty()) {
				System.out.println(path + "没有节点");
			} else {
				res = true;
				System.out.println("节点列表");
				for (String child : list) {
					System.out.println(child);
				}
			}
		} catch (Exception e) {
			// e.printStackTrace();
		}
		return res;
	}

	public byte[] getData(String path) throws KeeperException, InterruptedException {
		return this.zookeeper.getData(path, false, null);
	}

	public static void main(String[] args) {
		try {
			ZookeeperService zookeeperService = new ZookeeperService();

			zookeeperService.connect("localhost");
			String zktest = "Zookeeper的JAVA API 测试";

			zookeeperService.Create();
			zookeeperService.getChild("/");
			// zookeeperService.close();

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

//启动方法,
public static void main(String[] args) {
		SetZookeeperInfo();
		SpringApplication.run(Application.class, args);
	}
	
	public static void SetZookeeperInfo()
	{
		ZookeeperService zookeeperService = new ZookeeperService();
		try {
			zookeeperService.connect("localhost");
			
			if(!zookeeperService.Exist())
			{
				zookeeperService.Create();
			}
			zookeeperService.getChild("/");

		} catch (Exception e) {
			e.printStackTrace();
		}
	}