zookeeper原生API做java客户端

简介

本文是使用apache提供的原生api做zookeeper客户端

• jar包

      zookeeper-3.4.5.jar

•   Demo

• package bjsxt.zookeeper.base;
  
  import java.util.concurrent.CountDownLatch;
  
  import org.apache.zookeeper.AsyncCallback;
  import org.apache.zookeeper.WatchedEvent;
  import org.apache.zookeeper.Watcher;
  import org.apache.zookeeper.Watcher.Event.EventType;
  import org.apache.zookeeper.ZooKeeper;
  import org.apache.zookeeper.Watcher.Event.KeeperState;
  
  /**
   * Zookeeper 原生api实践
   * @since 2017-6-13
   */
  public class ZookeeperBase {
  
      /** zookeeper地址 */
      static final String CONNECT_ADDR = "192.168.0.4:2181,192.168.0.5:2181,192.168.0.6:2181";
      /** session超时时间 */
      static final int SESSION_OUTTIME = 2000;//ms 
      /** 信号量，阻塞程序执行，用于等待zookeeper连接成功，发送成功信号 */
      static final CountDownLatch connectedSemaphore = new CountDownLatch(1);
      
      public static void main(String[] args) throws Exception{
          
          ZooKeeper zk = new ZooKeeper(CONNECT_ADDR, SESSION_OUTTIME, new Watcher(){
              @Override
              public void process(WatchedEvent event) {
                  //获取事件的状态
                  KeeperState keeperState = event.getState();
                  EventType eventType = event.getType();
                  //如果是建立连接
                  if(KeeperState.SyncConnected == keeperState){
                      if(EventType.None == eventType){
                          //如果建立连接成功，则发送信号量，让后续阻塞程序向下执行
                          connectedSemaphore.countDown();
                          System.out.println("zk 建立连接");
                      }
                  }
              }
          });
  
          //进行阻塞
          connectedSemaphore.await();
          
          System.out.println("..");
          //创建父节点
          //zk.create("/testRoot", "testRoot".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
          
          //创建子节点
  //        String ret = zk.create("/testRoot/children", "children data".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
  //        System.out.println("创建子节点"+ret);
          //获取节点洗信息
          /*byte[] data = zk.getData("/testRoot", false, null);
          System.out.println(new String(data));
          System.out.println(zk.getChildren("/testRoot", false));*/
          
          //修改节点的值
  /*        zk.setData("/testRoot", "modify data root".getBytes(), -1);
          byte[] data = zk.getData("/testRoot", false, null);
          System.out.println(new String(data));    */    
          
          //判断节点是否存在
  //        System.out.println(zk.exists("/testRoot/children", false));
          //同步删除节点
          zk.delete("/testRoot/children", -1);   
          //异步删除节点
          zk.delete("/testRoot/children", -1, new AsyncCallback.VoidCallback() {
              @Override
              public void processResult(int rc, String path, Object ctx) {
                  System.out.println("rc====="+rc);
                  System.out.println("path======"+path);
                  System.out.println("ctc======"+path);
              }
          } , "回调值");
  //        System.out.println(zk.exists("/testRoot/children", false));
          
          zk.close();
          
          
          
      }
      
  }

  总结：

• 在这里api对zookeeper节点进行增删改查，有同步和异步的方式
• zookeeper不支持递归创建子节点（也就是说在父节点不存在的情况下，不允许创建子节点）
• zookeeper不支持递归删除（也就是说在父节点有子节点的情况下，不允许直接删除父节点）