zookeeper客户端使用第三方(Curator)封装的Api操作节点

• 为什么使用Curator?

1. Curator本身是Netflix公司开源的zookeeper客户端；
2. Curator 提供了各种应用场景的实现封装；
3. curator-framework 提供了fluent风格api；
4. curator-replice 提供了实现封装；

• 引入依赖：

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>2.11.0</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>2.11.0</version>
</dependency>

• 创建会话连接

 package com.karat.cn.zookeeper.curator;

 import org.apache.curator.framework.CuratorFramework;
 import org.apache.curator.framework.CuratorFrameworkFactory;
 import org.apache.curator.retry.ExponentialBackoffRetry;

 /**
  * 创建会话连接
  * @author Administrator
  *
  */
 public class CuratorCreateSessionDemo {
     private final static String CONNECTSTRING="47.107.121.215:2181";

     public static void main(String args[]) {
         //创建会话连接的2种方式
         //正常的风格
         CuratorFramework curatorFramework1=CuratorFrameworkFactory.
                 newClient(CONNECTSTRING,5000,5000,
                         new ExponentialBackoffRetry(1000, 3));//重试机制
         curatorFramework1.start();
         //fluent风格
         CuratorFramework curatorFramework2=CuratorFrameworkFactory.builder().
                     connectString(CONNECTSTRING).
                     sessionTimeoutMs(5000).
                     retryPolicy(new ExponentialBackoffRetry(1000, 3)).build();
         curatorFramework2.start();
         System.out.println("success");

     }
 }

• curator连接的重试策略

ExponentialBackoffRetry()  衰减重试
RetryNTimes 指定最大重试次数
RetryOneTime 仅重试一次
RetryUnitilElapsed 一直重试知道规定的时间

• 节点操作

 package com.karat.cn.zookeeper.curator;

 import org.apache.curator.framework.CuratorFramework;
 import org.apache.curator.framework.CuratorFrameworkFactory;
 import org.apache.curator.framework.api.BackgroundCallback;
 import org.apache.curator.framework.api.CuratorEvent;
 import org.apache.curator.framework.api.transaction.CuratorTransactionResult;
 import org.apache.curator.retry.ExponentialBackoffRetry;
 import org.apache.zookeeper.CreateMode;
 import org.apache.zookeeper.data.Stat;

 import java.util.Collection;
 import java.util.Collections;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;

 /**
  * curator对节点的增删改查
  * @author Administrator
  *
  */
 public class CuratorOperatorDemo {

     public static void main(String[] args) throws InterruptedException {
         CuratorFramework curatorFramework=CuratorClientUtils.getInstance();
         System.out.println("连接成功.........");

         //fluent风格api增删改查操作
         /**
          * 创建节点
          */
        /*try {
             String result=curatorFramework.create()
                     .creatingParentsIfNeeded()//创建父节点
                     .withMode(CreateMode.PERSISTENT)//持久节点：节点创建后，会一直存在，不会因客户端会话失效而删除；
                     .forPath("/curator/curator1/curator11","123".getBytes());
             System.out.println(result);
         } catch (Exception e) {
             e.printStackTrace();
         }*/
         /**
          * 删除节点
          */
         /*try {
             //默认情况下，version为-1
             curatorFramework.delete()//删除操作
             .deletingChildrenIfNeeded()//删除子节点
             .forPath("/node");
         } catch (Exception e) {
             e.printStackTrace();
         }*/

         /**
          * 查询
          */
         /*Stat stat=new Stat();
         try {
             byte[] bytes=curatorFramework
                     .getData()
                     .storingStatIn(stat)
                     .forPath("/curator/curator1/curator11");
             System.out.println(new String(bytes)+"-->stat:"+stat);
         } catch (Exception e) {
             e.printStackTrace();
         }*/
         /**
          * 更新
          */
         /*try {
             Stat stat=curatorFramework
                     .setData()
                     .forPath("/curator","lijing".getBytes());
             System.out.println(stat);
         } catch (Exception e) {
             e.printStackTrace();
         }*/

         /**
          * 异步操作
          */
         /*ExecutorService service= Executors.newFixedThreadPool(1);//线程池(创建节点的事件由线程池处理)
         CountDownLatch countDownLatch=new CountDownLatch(1);//计数器
         try {
             curatorFramework
             .create()
             .creatingParentsIfNeeded()
             .withMode(CreateMode.EPHEMERAL)
             .inBackground(new BackgroundCallback() {
                  @Override
                  public void processResult(CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception {
                      System.out.println(Thread.currentThread().getName()
                              +"->resultCode:"
                              +curatorEvent.getResultCode()+"->"//响应结果
                              +curatorEvent.getType());//当前节点操作类型
                      countDownLatch.countDown();
                  }
             },service)
             .forPath("/mic","123".getBytes());
         } catch (Exception e) {
             e.printStackTrace();
         }
         countDownLatch.await();//等待(让当前线程等待)
         service.shutdown();//关闭线程*/
         /**
          * 事务操作（curator独有的）
          */
         try {
             Collection<CuratorTransactionResult> resultCollections=curatorFramework
                     .inTransaction()//开启一个事务
                     .create()
                     .forPath("/trans","111".getBytes())//创建一个节点
                     .and()//通过and去修改一个节点
                     .setData()
                     .forPath("/curator","111".getBytes())//当修改节点不存在，则一成功一失败，事务不会提交成功
                     .and()
                     .commit();//提交事务
             for (CuratorTransactionResult result:resultCollections){
                 System.out.println(result.getForPath()+"->"+result.getType());
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 }

• 将会话连接做成工具类

 package com.karat.cn.zookeeper.curator;

 import org.apache.curator.framework.CuratorFramework;
 import org.apache.curator.framework.CuratorFrameworkFactory;
 import org.apache.curator.retry.ExponentialBackoffRetry;

 /**
  * 会话连接工具类
  * @author Administrator
  *
  */
 public class CuratorClientUtils {

     private static CuratorFramework curatorFramework;

     private final static String CONNECTSTRING="47.107.121.215:2181";

     public static CuratorFramework getInstance(){
         curatorFramework= CuratorFrameworkFactory.
                 newClient(CONNECTSTRING,5000,5000,
                         new ExponentialBackoffRetry(1000,3));
         curatorFramework.start();
         return curatorFramework;
     }
 }

• 监听

 package com.karat.cn.zookeeper.curator;

 import org.apache.curator.framework.CuratorFramework;
 import org.apache.curator.framework.recipes.cache.NodeCache;
 import org.apache.curator.framework.recipes.cache.PathChildrenCache;
 import org.apache.zookeeper.CreateMode;

 import java.util.concurrent.TimeUnit;

 /**
  * 监听
  * @author Administrator
  *
  */
 public class CuratorEventDemo {

     /**
      * 三种watcher来做节点的监听
      * pathcache   监视一个路径下子节点的创建、删除、节点数据更新
      * NodeCache   监视一个节点的创建、更新、删除
      * TreeCache   pathcaceh+nodecache 的合体（监视路径下的创建、更新、删除事件），
      * 缓存路径下的所有子节点的数据
      */

     public static void main(String[] args) throws Exception {
         CuratorFramework curatorFramework=CuratorClientUtils.getInstance();
         /**
          * 节点变化NodeCache
          */
         //监听
         /*NodeCache cache=new NodeCache(curatorFramework,"/curator",false);
         cache.start(true);
         //监听事件
         cache.getListenable().addListener(()-> System.out.println("节点数据发生变化,变化后的结果" +
                 "："+new String(cache.getCurrentData().getData())));
         //修改节点
         curatorFramework.setData().forPath("/curator","666".getBytes());*/

         /**
          * PatchChildrenCache
          */

         PathChildrenCache cache=new PathChildrenCache(curatorFramework,"/event",true);//参数2监听的节点，参数3是否缓存
         cache.start(PathChildrenCache.StartMode.POST_INITIALIZED_EVENT);
         // Normal/ BUILD_INITIAL_CACHE /POST_INITIALIZED_EVENT

         cache.getListenable().addListener((curatorFramework1,pathChildrenCacheEvent)->{
             switch (pathChildrenCacheEvent.getType()){
                 case CHILD_ADDED:
                     System.out.println("增加子节点");
                     break;
                 case CHILD_REMOVED:
                     System.out.println("删除子节点");
                     break;
                 case CHILD_UPDATED:
                     System.out.println("更新子节点");
                     break;
                 default:break;
             }
         });
         //创建节点
         curatorFramework.create().withMode(CreateMode.PERSISTENT).forPath("/event","event".getBytes());
         TimeUnit.SECONDS.sleep(1);
         System.out.println("1");
         //创建子节点
         curatorFramework.create().withMode(CreateMode.EPHEMERAL).forPath("/event/event1","1".getBytes());
         TimeUnit.SECONDS.sleep(1);
         System.out.println("2");
         //修改节点
         curatorFramework.setData().forPath("/event/event1","222".getBytes());
         TimeUnit.SECONDS.sleep(1);
         System.out.println("3");
         //删除节点
         curatorFramework.delete().forPath("/event/event1");
         System.out.println("4");

         System.in.read();
     }
 }