ZooKeeper入门（三）zookeeper的Watcher机制

process方法是Watcher接口中的一个回调方法，当ZooKeeper向客户端发送一个Watcher事件通知时，客户端就会对相应的process方法进行回调，从而实现对事件的处理。


import java.util.concurrent.CountDownLatch;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;public class WatcherZookeeper implements Watcher{// 集群连接地址private static final String CONNECT_ADDRES = "127.0.0.1:2181";// 会话超时时间private static final int SESSIONTIME = 2000;// 信号量,让zk在连接之前等待,连接成功后才能往下走.private static final CountDownLatch countDownLatch = new CountDownLatch(1);private static String LOG_MAIN = "【main】 ";private ZooKeeper zk;public void createConnection(String connectAddres, int sessionTimeOut) {try {zk = new ZooKeeper(connectAddres, sessionTimeOut, this);System.out.println(LOG_MAIN + "zk 开始启动连接服务器....");countDownLatch.await();} catch (Exception e) {e.printStackTrace();}}public boolean createPath(String path, String data) {try {this.exists(path, true);this.zk.create(path, data.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);System.out.println(LOG_MAIN + "节点创建成功, Path:" + path + ",data:" + data);} catch (Exception e) {e.printStackTrace();return false;}return true;}/*** 判断指定节点是否存在* * @param path*            节点路径*/public Stat exists(String path, boolean needWatch) {try {return this.zk.exists(path, needWatch);} catch (Exception e) {e.printStackTrace();return null;}}public boolean updateNode(String path,String data) throws KeeperException, InterruptedException {exists(path, true);this.zk.setData(path, data.getBytes(), -1);return false;}public void process(WatchedEvent watchedEvent) {// 获取事件状态KeeperState keeperState = watchedEvent.getState();// 获取事件类型EventType eventType = watchedEvent.getType();// zk 路径String path = watchedEvent.getPath();System.out.println("进入到 process() keeperState:" + keeperState + ", eventType:" + eventType + ", path:" + path);// 判断是否建立连接if (KeeperState.SyncConnected == keeperState) {if (EventType.None == eventType) {// 如果建立建立成功,让后程序往下走System.out.println(LOG_MAIN + "zk 建立连接成功!");countDownLatch.countDown();} else if (EventType.NodeCreated == eventType) {System.out.println(LOG_MAIN + "事件通知,新增node节点" + path);} else if (EventType.NodeDataChanged == eventType) {System.out.println(LOG_MAIN + "事件通知,当前node节点" + path + "被修改....");}else if (EventType.NodeDeleted == eventType) {System.out.println(LOG_MAIN + "事件通知,当前node节点" + path + "被删除....");}}System.out.println("--------------------------------------------------------");}public static void main(String[] args) throws KeeperException, InterruptedException {WatcherZookeeper zkClientWatcher = new WatcherZookeeper();zkClientWatcher.createConnection(CONNECT_ADDRES, SESSIONTIME);boolean createResult = zkClientWatcher.createPath("/qushenWatcher", "pa-644064");}}

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