1.Curator Cache 與原生ZooKeeper Wacher區別

? ?原生的ZooKeeper Wacher是一次性的：一個Wacher一旦觸發就會被移出，如果你想要反復使用Wacher，就要在Wacher被移除后重新注冊，使用起來很麻煩。使用Curator Cache 可以反復使用Wacher了。

2.Curator Cache 和Curator Wacher區別

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2.相關類

Curator Cache主要提供了一下三組類，分別用于實現對節點的監聽，子節點的監聽和二者的混合：

? 1.NodeCache,NodeCacheListener，ChildData，節點創建，節點數據內容變更，不能監聽節點刪除。

? 2.PathChildrenCache，PathChildrenCacheListener，PathChildrenCacheEvent監聽指定節點的子節點的變更包括添加，刪除，子節點數據數據變更這三類。

? 3.TreeCache，TreeCacheListener，TreeCacheEvent，TreeCacheSelector

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3.節點監聽

package cn.francis.maven.hello.ZooKeeper;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.NodeCache;
import org.apache.curator.framework.recipes.cache.NodeCacheListener;
import org.apache.curator.framework.recipes.cache.TreeCache;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.test.TestingServer;
import org.apache.curator.utils.CloseableUtils;
import org.apache.zookeeper.CreateMode;public class NodeCacheDemo {public static void main(String[]args) throws Exception{TestingServer server=null;CuratorFramework client=null;NodeCache nodeCache=null;String path="/francis/nodecache/a";try{ server=new TestingServer();client= CuratorFrameworkFactory.newClient(server.getConnectString(), new ExponentialBackoffRetry(1000,3));client.start();path=client.create().creatingParentsIfNeeded().withProtection().withMode(CreateMode.EPHEMERAL).forPath(path,"init".getBytes());nodeCache=new NodeCache(client,path,false);nodeCache.start();addListener(nodeCache);client.setData().forPath(path,"hello".getBytes());Thread.sleep(1000);client.delete().deletingChildrenIfNeeded().forPath(path);Thread.sleep(Integer.MAX_VALUE);}catch(Exception e){e.printStackTrace();}finally{//這里因為是測試，沒有加他們。//CloseableUtils.closeQuietly(nodeCache);/// CloseableUtils.closeQuietly(client);// CloseableUtils.closeQuietly(server);
      }     }public static void addListener(NodeCache nodeCache){//監聽類型：節點是否存在，節點數據內容改變，不監聽節點刪除。nodeCache.getListenable().addListener(new NodeCacheListener(){@Overridepublic void nodeChanged() throws Exception {// TODO Auto-generated method stubif(nodeCache.getCurrentData()!=null)System.out.println("path:"+nodeCache.getCurrentData().getPath()+",data:"+new String(nodeCache.getCurrentData().getData()));}});}
}

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在上面的代碼中首先創建了一個節點，然后創建用這個節點路徑來創建NodeCache，啟動NodeCache，添加NodeCacheListener。然后調用setData來修改節點數據。上面的代碼輸入如下：

path:/francis/nodecache/_c_d5be73ca-592c-4eda-b7c4-c8ec60ef39a8-a,data:hello

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子節點監聽：

?PathChildrenCache的構造函數如下：

public PathChildrenCache(CuratorFramework client,String path,boolean cacheData)
Parameters:
client - the client
path - path to watch
cacheData - if true, node contents are cached in addition to the stat

其中最主要的是cacheData，如果為true，那么當對子節點調用setData時，PathChildrenCache會受到這個CHILD_UPDATED事件。

下面看一下demo：

package cn.francis.maven.hello.ZooKeeper;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.NodeCache;
import org.apache.curator.framework.recipes.cache.NodeCacheListener;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCache.StartMode;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.framework.recipes.cache.TreeCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent.Type;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.test.TestingServer;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.utils.ZKPaths;
import org.apache.hadoop.mapred.join.Parser.TType;
import org.apache.zookeeper.CreateMode;public class NodeCacheDemo {public static void main(String[]args) throws Exception{TestingServer server=null;CuratorFramework client=null;NodeCache nodeCache=null;String path="/francis/nodecache/b";try{ server=new TestingServer();client= CuratorFrameworkFactory.newClient(server.getConnectString(),new ExponentialBackoffRetry(1000,3));client.start();//這里將第三個參數cacheData設置為true，這樣當對子節點調用setData時，會受到CHILDREN_UPDATE通知。PathChildrenCache childrenCache=new PathChildrenCache(client,path,true);
         childrenCache.start(StartMode.POST_INITIALIZED_EVENT);childrenCache.getListenable().addListener(new PathChildrenCacheListener(){@Overridepublic void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception {// TODO Auto-generated method stubif(event.getType()==Type.INITIALIZED){System.out.println("create"+event.getData().getPath());    }else if(event.getType()==Type.CHILD_ADDED){System.out.println("create"+event.getData().getPath());                   }else if(event.getType()==Type.CHILD_REMOVED){System.out.println("remove:"+event.getData().getPath());}else if(event.getType()==Type.CHILD_UPDATED){//System.out.println("update:"+event.getData().getPath());System.out.println("update:"+new String(event.getData().getData()));}}});//創建父節點System.out.println(client.create().creatingParentsIfNeeded().withMode(CreateMode.PERSISTENT).forPath(path,"init".getBytes()));Thread.sleep(1000);//創建子節點String childPath1=ZKPaths.makePath(path, "a");childPath1=client.create().withMode(CreateMode.PERSISTENT).forPath(childPath1,"1".getBytes());Thread.sleep(1000);//對子節點賦值client.setData().forPath(childPath1,"aaa".getBytes());Thread.sleep(1000);//刪除子節點
         client.delete().forPath(childPath1);client.delete().deletingChildrenIfNeeded().forPath("/francis");Thread.sleep(2000);}catch(Exception e){e.printStackTrace();}finally{
          CloseableUtils.closeQuietly(nodeCache);CloseableUtils.closeQuietly(client);CloseableUtils.closeQuietly(server);}     }

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3.TreeNodeCache

? ?TreeNodeCache將NodeCache和PathChildrenCache功能結合到一起了。他不僅可以對子節點和父節點同時進行監聽。如下：

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package cn.francis.maven.hello.ZooKeeper;import java.util.Map;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.NodeCache;
import org.apache.curator.framework.recipes.cache.NodeCacheListener;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCache.StartMode;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.framework.recipes.cache.TreeCache;
import org.apache.curator.framework.recipes.cache.TreeCacheEvent;
import org.apache.curator.framework.recipes.cache.TreeCacheListener;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent.Type;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.test.TestingServer;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.utils.ZKPaths;
import org.apache.hadoop.mapred.join.Parser.TType;
import org.apache.zookeeper.CreateMode;public class NodeCacheDemo {public static void main(String[]args) throws Exception{TestingServer server=null;CuratorFramework client=null;NodeCache nodeCache=null;String path="/francis/nodecache/b";try{ server=new TestingServer();client= CuratorFrameworkFactory.newClient(server.getConnectString(),new ExponentialBackoffRetry(1000,3));client.start();TreeCache treeNodeCache=new TreeCache(client,path);treeNodeCache.start();treeNodeCache.getListenable().addListener(new TreeCacheListener(){@Overridepublic void childEvent(CuratorFramework client, TreeCacheEvent event) throws Exception {// TODO Auto-generated method stubswitch(event.getType()){case NODE_ADDED:System.out.println("added:"+event.getData().getPath());break;case NODE_UPDATED:System.out.println("updated:"+event.getData().getPath());break;case NODE_REMOVED: System.out.println("removed:"+event.getData().getPath());break;default:System.out.println("other:"+event.getType());}}});//創建父節點client.create().creatingParentsIfNeeded().withMode(CreateMode.PERSISTENT).forPath(path,"init".getBytes());Thread.sleep(1000);//創建子節點String childPath1=ZKPaths.makePath(path, "a");childPath1=client.create().withMode(CreateMode.PERSISTENT).forPath(childPath1,"1".getBytes());Thread.sleep(1000);//對子節點賦值client.setData().forPath(childPath1,"aaa".getBytes());Thread.sleep(1000);//對子節點賦值client.setData().forPath(path,"aaa".getBytes());Thread.sleep(1000);//刪除子節點
         client.delete().forPath(childPath1);client.delete().deletingChildrenIfNeeded().forPath("/francis");Thread.sleep(2000);}catch(Exception e){e.printStackTrace();}finally{//這里因為是測試，沒有加他們。
          CloseableUtils.closeQuietly(nodeCache);CloseableUtils.closeQuietly(client);CloseableUtils.closeQuietly(server);}     }
}

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輸出如下：

other:INITIALIZED
added:/francis/nodecache/b
added:/francis/nodecache/b/a
updated:/francis/nodecache/b/a
updated:/francis/nodecache/b
removed:/francis/nodecache/b/a
removed:/francis/nodecache/b

轉載于:https://www.cnblogs.com/francisYoung/p/5483777.html

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