Zookeeper开源客户端框架Curator简介与示例
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简介
Curator最初由Netflix的Jordan Zimmerman开发, Curator提供了一套Java类库， 可以更容易的使用ZooKeeper.
所谓ZooKeeper技巧(ZooKeeper Recipes)，也可以称之为解决方案， 或者叫实现方案， 是指ZooKeeper的使用方法， 比如分布式的配置管理， Leader选举等
Curator作为Apache ZooKeeper天生配套的组件。ZooKeeper的Java开发者自然而然的会选择它在项目中使用。
官网链接：http://curator.apache.org/
提供的功能组件
Framework 提供了一套高级的API， 简化了ZooKeeper的操作。 它增加了很多使用ZooKeeper开发的特性，可以处理ZooKeeper集群复杂的连接管理和重试机制
Client是ZooKeeper客户端的一个替代品, 提供了一些底层处理和相关的工具方法
Recipes实现了通用ZooKeeper的recipe, 该组件建立在Framework的基础之上
Utilities各种工具类
Errors异常处理, 连接, 恢复等.
Extensionscurator-recipes包实现了通用的技巧，这些技巧在ZooKeeper文档中有介绍。为了避免是这个包(package)变得巨大， recipes/applications将会放入一个独立的extension包下。并使用命名规则curator-x-name.
Curator 编译好的类库被发布到Maven Center中。Curator包含几个artifact. 你可以根据你的需要在你的项目中加入相应的依赖。对于大多数开发者来说，引入curator-recipes这一个就足够了
<dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-recipes</artifactId> <version>2.6.0</version></dependency> <dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-client</artifactId> <version>2.6.0</version></dependency><dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-framework</artifactId> <version>2.6.0</version></dependency>
代码示例
import java.util.List;import java.util.Map;import java.util.concurrent.TimeUnit;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.framework.api.CuratorEvent;import org.apache.curator.framework.api.CuratorListener;import org.apache.curator.framework.api.CuratorWatcher;import org.apache.curator.framework.api.GetChildrenBuilder;import org.apache.curator.framework.api.GetDataBuilder;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.curator.utils.ZKPaths;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.Watcher.Event.KeeperState;import org.apache.zookeeper.data.Stat;import com.google.common.base.Charsets;import com.google.common.base.Objects;import com.google.common.base.Strings;import com.google.common.collect.Lists;import com.google.common.collect.Maps;/** * DateTime: 2015年1月9日 上午9:14:08 * */public class CuratorTest { private static String zkAddress = "hadoop02:2181,hadoop03:2181,hadoop04:2181"; public static void main(String[] args) throws Exception { CuratorUtil curator = new CuratorUtil(zkAddress); curator.createNode("/zkroot/test1", "你好abc11"); curator.createNode("/zkroot/test2", "你好abc22"); curator.updateNode("/zkroot/test2", "你好abc22"); List<String> list = curator.listChildren("/zkroot"); Map<String, String> map = curator.listChildrenDetail("/zkroot"); // curator.deleteNode("/zkroot"); // curator.destory(); System.out.println("========================================="); for (String str : list) { System.out.println(str); } System.out.println("========================================="); for (Map.Entry<String, String> entry : map.entrySet()) { System.out.println(entry.getKey() + "=>" + entry.getValue()); } // 增加监听 curator.addWatch("/zkroot", false); TimeUnit.SECONDS.sleep(600); }}class CuratorUtil { private CuratorFramework client; public CuratorUtil(String zkAddress) { client = CuratorFrameworkFactory.newClient(zkAddress, new ExponentialBackoffRetry(1000, 3)); client.getCuratorListenable().addListener(new NodeEventListener()); client.start(); } /** * 创建node * * @param nodeName * @param value * @return */ public boolean createNode(String nodeName, String value) { boolean suc = false; try { Stat stat = getClient().checkExists().forPath(nodeName); if (stat == null) { String opResult = null; if (Strings.isNullOrEmpty(value)) { opResult = getClient().create().creatingParentsIfNeeded().forPath(nodeName); } else { opResult = getClient().create().creatingParentsIfNeeded() .forPath(nodeName, value.getBytes(Charsets.UTF_8)); } suc = Objects.equal(nodeName, opResult); } } catch (Exception e) { e.printStackTrace(); } return suc; } /** * 更新节点 * * @param nodeName * @param value * @return */ public boolean updateNode(String nodeName, String value) { boolean suc = false; try { Stat stat = getClient().checkExists().forPath(nodeName); if (stat != null) { Stat opResult = getClient().setData().forPath(nodeName, value.getBytes(Charsets.UTF_8)); suc = opResult != null; } } catch (Exception e) { e.printStackTrace(); } return suc; } /** * 删除节点 * * @param nodeName */ public void deleteNode(String nodeName) { try { getClient().delete().deletingChildrenIfNeeded().forPath(nodeName); } catch (Exception e) { e.printStackTrace(); } } /** * 找到指定节点下所有子节点的名称与值 * * @param node * @return */ public Map<String, String> listChildrenDetail(String node) { Map<String, String> map = Maps.newHashMap(); try { GetChildrenBuilder childrenBuilder = getClient().getChildren(); List<String> children = childrenBuilder.forPath(node); GetDataBuilder dataBuilder = getClient().getData(); if (children != null) { for (String child : children) { String propPath = ZKPaths.makePath(node, child); map.put(child, new String(dataBuilder.forPath(propPath), Charsets.UTF_8)); } } } catch (Exception e) { e.printStackTrace(); } return map; } /** * 列出子节点的名称 * * @param node * @return */ public List<String> listChildren(String node) { List<String> children = Lists.newArrayList(); try { GetChildrenBuilder childrenBuilder = getClient().getChildren(); children = childrenBuilder.forPath(node); } catch (Exception e) { e.printStackTrace(); } return children; } /** * 增加监听 * * @param node * @param isSelf * true 为node本身增加监听 false 为node的子节点增加监听 * @throws Exception */ public void addWatch(String node, boolean isSelf) throws Exception { if (isSelf) { getClient().getData().watched().forPath(node); } else { getClient().getChildren().watched().forPath(node); } } /** * 增加监听 * * @param node * @param isSelf * true 为node本身增加监听 false 为node的子节点增加监听 * @param watcher * @throws Exception */ public void addWatch(String node, boolean isSelf, Watcher watcher) throws Exception { if (isSelf) { getClient().getData().usingWatcher(watcher).forPath(node); } else { getClient().getChildren().usingWatcher(watcher).forPath(node); } } /** * 增加监听 * * @param node * @param isSelf * true 为node本身增加监听 false 为node的子节点增加监听 * @param watcher * @throws Exception */ public void addWatch(String node, boolean isSelf, CuratorWatcher watcher) throws Exception { if (isSelf) { getClient().getData().usingWatcher(watcher).forPath(node); } else { getClient().getChildren().usingWatcher(watcher).forPath(node); } } /** * 销毁资源 */ public void destory() { if (client != null) { client.close(); } } /** * 获取client * * @return */ public CuratorFramework getClient() { return client; }}// 监听器final class NodeEventListener implements CuratorListener { @Override public void eventReceived(CuratorFramework client, CuratorEvent event) throws Exception { System.out.println(event.toString() + "......................."); final WatchedEvent watchedEvent = event.getWatchedEvent(); if (watchedEvent != null) { System.out.println(watchedEvent.getState() + "=======================" + watchedEvent.getType()); if (watchedEvent.getState() == KeeperState.SyncConnected) { switch (watchedEvent.getType()) { case NodeChildrenChanged: // TODO break; case NodeDataChanged: // TODO break; default: break; } } } }http://my.oschina.net/cloudcoder/blog?disp=2&p=1&catalog=418649
http://supben.iteye.com/blog/2094077
package com.cyyun;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.curator.utils.CloseableUtils;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.data.Stat;public class CrudExamples {private static CuratorFramework client = get();private static final String PATH = "/crud";public static void main(String[] args) {try {client.start();client.create().forPath(PATH, "I love messi".getBytes());byte[] bs = client.getData().forPath(PATH);System.out.println("新建的节点，data为:" + new String(bs));// 注册观察者，当节点变动时触发client.getData().usingWatcher(new Watcher() {@Overridepublic void process(WatchedEvent event) {System.out.println("node is changed");}}).inBackground().forPath(PATH);client.setData().forPath(PATH, "I love football".getBytes());// 注册观察者，当节点变动时触发client.getData().usingWatcher(new Watcher() {@Overridepublic void process(WatchedEvent event) {System.out.println("node is changed");}}).inBackground().forPath(PATH);client.setData().forPath(PATH, "I love foot2222ball".getBytes());System.out.println(new String(client.getData().forPath(PATH)));// 由于是在background模式下获取的data，此时的bs可能为nullbyte[] bs2 = client.getData().watched().inBackground().forPath(PATH);System.out.println("修改后的data为"+ new String(bs2 != null ? bs2 : new byte[0]));client.delete().forPath(PATH);Stat stat = client.checkExists().forPath(PATH);// Stat就是对zonde所有属性的一个映射， stat=null表示节点不存在！System.out.println(stat);} catch (Exception e) {e.printStackTrace();} finally {CloseableUtils.closeQuietly(client);}}public static CuratorFramework get() {String zookeeperConnectionString = "127.0.0.1:4180,127.0.0.1:5180,127.0.0.1:6180";CuratorFramework client = CuratorFrameworkFactory.builder().connectString(zookeeperConnectionString).sessionTimeoutMs(30000).connectionTimeoutMs(30000).canBeReadOnly(false).retryPolicy(new ExponentialBackoffRetry(1000, Integer.MAX_VALUE)).namespace("zk").defaultData(null).build();return client;}}
