zookeeper知识点三(判断节点是否存在)_zk节点不存在-优快云博客

该博客介绍了一个Java实现的ZooKeeper客户端，用于检查节点是否存在并设置监听。通过ZooKeeper的`exists()`方法判断节点状态，同时在节点创建、数据变更和删除时触发相应的事件处理。

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public class NodeExistsSync implements Watcher{

    private static ZooKeeper zooKeeper;
    private static Stat stat = new Stat();
   public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
       zooKeeper = new ZooKeeper("127.0.0.1:2181",5000,new NodeExistsSync());
       System.out.println(zooKeeper.getState().toString());
       Thread.sleep(Integer.MAX_VALUE);
   }

   private void doSomething(ZooKeeper zooKeeper){
       try{
           Stat stat = zooKeeper.exists("/node_5", true);
           if(stat == null){
               System.out.println("节点不存在");
           }else{
               System.out.println("doSomething-stat:" + stat);
           }
       }catch(Exception e){
       }
   }

   @Override
   public void process(WatchedEvent event) {
       System.out.println("事件状态:" + event.getState() +",事件类型:" + event.getType() +",事件涉及路径:" + event.getPath());
       if (event.getState()==KeeperState.SyncConnected){
           if (event.getType()==EventType.None && null==event.getPath()){
               doSomething(zooKeeper);
           }else{
               try {
                   if (event.getType()==EventType.NodeCreated){
                       System.out.println(event.getPath()+" created");
                       System.out.println(zooKeeper.exists(event.getPath(), true));
                       System.out.println(zooKeeper.getData(event.getPath(), false, stat));
                   }
                   else if (event.getType()==EventType.NodeDataChanged){
                       System.out.println(event.getPath()+" updated");
                       System.out.println(zooKeeper.exists(event.getPath(), true));
                       System.out.println(zooKeeper.getData(event.getPath(), false, stat));
                   }
                   else if (event.getType()==EventType.NodeDeleted){
                       System.out.println(event.getPath()+" deleted");
                       System.out.println(zooKeeper.exists(event.getPath(), true));
                   }

               } catch (Exception e) {
               }

           }

       }
   }
}