1.Curator Cache 與原生ZooKeeper Wacher區(qū)別

? ?原生的ZooKeeper Wacher是一次性的：一個(gè)Wacher一旦觸發(fā)就會(huì)被移出，如果你想要反復(fù)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(fù)使用Wacher了。

2.Curator Cache 和Curator Wacher區(qū)別

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2.相關(guān)類

Curator Cache主要提供了一下三組類，分別用于實(shí)現(xiàn)對節(jié)點(diǎn)的監(jiān)聽，子節(jié)點(diǎn)的監(jiān)聽和二者的混合：

? 1.NodeCache,NodeCacheListener，ChildData，節(jié)點(diǎn)創(chuàng)建，節(jié)點(diǎn)數(shù)據(jù)內(nèi)容變更，不能監(jiān)聽節(jié)點(diǎn)刪除。

? 2.PathChildrenCache，PathChildrenCacheListener，PathChildrenCacheEvent監(jiān)聽指定節(jié)點(diǎn)的子節(jié)點(diǎn)的變更包括添加，刪除，子節(jié)點(diǎn)數(shù)據(jù)數(shù)據(jù)變更這三類。

? 3.TreeCache，TreeCacheListener，TreeCacheEvent，TreeCacheSelector

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3.節(jié)點(diǎn)監(jiān)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?yàn)槭菧y試，沒有加他們。//CloseableUtils.closeQuietly(nodeCache);/// CloseableUtils.closeQuietly(client);// CloseableUtils.closeQuietly(server);
      }     }public static void addListener(NodeCache nodeCache){//監(jiān)聽類型：節(jié)點(diǎn)是否存在，節(jié)點(diǎn)數(shù)據(jù)內(nèi)容改變，不監(jiān)聽節(jié)點(diǎn)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(chuàng)建了一個(gè)節(jié)點(diǎn)，然后創(chuàng)建用這個(gè)節(jié)點(diǎn)路徑來創(chuàng)建NodeCache，啟動(dòng)NodeCache，添加NodeCacheListener。然后調(diào)用setData來修改節(jié)點(diǎn)數(shù)據(jù)。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(jié)點(diǎn)監(jiān)聽：

?PathChildrenCache的構(gòu)造函數(shù)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(dāng)對子節(jié)點(diǎn)調(diào)用setData時(shí)，PathChildrenCache會(huì)受到這個(gè)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(gè)參數(shù)cacheData設(shè)置為true，這樣當(dāng)對子節(jié)點(diǎn)調(diào)用setData時(shí)，會(huì)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(chuàng)建父節(jié)點(diǎn)System.out.println(client.create().creatingParentsIfNeeded().withMode(CreateMode.PERSISTENT).forPath(path,"init".getBytes()));Thread.sleep(1000);//創(chuàng)建子節(jié)點(diǎn)String childPath1=ZKPaths.makePath(path, "a");childPath1=client.create().withMode(CreateMode.PERSISTENT).forPath(childPath1,"1".getBytes());Thread.sleep(1000);//對子節(jié)點(diǎn)賦值client.setData().forPath(childPath1,"aaa".getBytes());Thread.sleep(1000);//刪除子節(jié)點(diǎn)
         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(jié)合到一起了。他不僅可以對子節(jié)點(diǎn)和父節(jié)點(diǎn)同時(shí)進(jìn)行監(jiān)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(chuàng)建父節(jié)點(diǎn)client.create().creatingParentsIfNeeded().withMode(CreateMode.PERSISTENT).forPath(path,"init".getBytes());Thread.sleep(1000);//創(chuàng)建子節(jié)點(diǎn)String childPath1=ZKPaths.makePath(path, "a");childPath1=client.create().withMode(CreateMode.PERSISTENT).forPath(childPath1,"1".getBytes());Thread.sleep(1000);//對子節(jié)點(diǎn)賦值client.setData().forPath(childPath1,"aaa".getBytes());Thread.sleep(1000);//對子節(jié)點(diǎn)賦值client.setData().forPath(path,"aaa".getBytes());Thread.sleep(1000);//刪除子節(jié)點(diǎn)
         client.delete().forPath(childPath1);client.delete().deletingChildrenIfNeeded().forPath("/francis");Thread.sleep(2000);}catch(Exception e){e.printStackTrace();}finally{//這里因?yàn)槭菧y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(zhuǎn)載于:https://www.cnblogs.com/francisYoung/p/5483777.html

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