zk 08之：Curator之一：zk客户端Curator
Curator是Netflix公司开源的一个Zookeeper客户端，与Zookeeper提供的原生客户端相比，Curator的抽象层次更高，简化了Zookeeper客户端编程。
它包含以下几个组件：
| Component | description |
|---|---|
| Recipes | Implementations of some of the common ZooKeeper “recipes”. The implementations are built on top of the Curator Framework. |
| Framework | The Curator Framework is a high-level API that greatly simplifies using ZooKeeper. It adds many features that build on ZooKeeper and handles the complexity of managing connections to the ZooKeeper cluster and retrying operations. |
| Utilities | Various utilities that are useful when using ZooKeeper. |
| Client | A replacement for the bundled ZooKeeper class that takes care of some low-level housekeeping and provides some useful utilities. |
| Errors | How Curator deals with errors, connection issues, recoverable exceptions, etc. |
| Extensions | The curator-recipes package implements the common recipes that are described in the ZooKeeper documentation. To avoid bloating that package, recipes/applications that have a vertical appeal will be put in separate “extension” packages using the naming convention curator-x-name. |
示例：
<?xml version="1.0"?> <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <modelVersion>4.0.0</modelVersion> <groupId>com.sf.zkclient</groupId> <artifactId>zkclient</artifactId> <version>0.0.1-SNAPSHOT</version> <name>zkclient</name> <url>http://maven.apache.org</url> <properties> <curator.version>2.11.1</curator.version> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId> <version>3.4.8</version> <exclusions> <exclusion> <artifactId>slf4j-log4j12</artifactId> <groupId>org.slf4j</groupId> </exclusion> <exclusion> <artifactId>log4j</artifactId> <groupId>log4j</groupId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-framework</artifactId> <version>${curator.version}</version> </dependency> <dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-client</artifactId> <version>${curator.version}</version> <exclusions> <exclusion> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>18.0</version> </dependency> </dependencies> </project>
java代码：
示例一：常见的添加、修改、删除示例：
public static void test() throws Exception { String address = "localhost:2181"; CuratorFramework client = CuratorFrameworkFactory.newClient(address, new ExponentialBackoffRetry(1000, 3)); try{ client.start(); String path = "/yongjiu2/yongjiu3/test5"; //a. 创建永久性节点 client.create() .creatingParentContainersIfNeeded() .withMode(CreateMode.PERSISTENT) .withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE) .forPath(path, "hello, zk".getBytes()); System.out.println("b"); //b. 创建临时节点 client.create().withMode(CreateMode.EPHEMERAL).forPath("/temptest5", "hello".getBytes()); System.out.println("c"); //c.获取节点值 byte[] buf = client.getData().forPath(path); System.out.println("get data path:"+path+", data:"+new String(buf)); System.out.println("d"); //d.设置节点值 client.setData().inBackground().forPath(path, "ricky".getBytes()); System.out.println("e"); //e.checkExists Stat stat = client.checkExists().forPath(path); if(stat==null){ System.out.println("exec create path:"+path); }else { System.out.println("exec getData"); } System.out.println("f"); //f.删除节点 client.delete().deletingChildrenIfNeeded().forPath(path); byte[] buf2 = client.getData().forPath(path); System.out.println("get data path:"+path+", data:"+new String(buf2)); }finally { if(client!=null) client.close(); } }
示例二：临时节点不能有子节点、不能级联创建示例：
/** * 级联创建临时节点测试，结果会创建不成功，报错 * @throws Exception */ public static void test2() throws Exception { String address = "localhost:2181"; CuratorFramework client = CuratorFrameworkFactory.newClient(address, new ExponentialBackoffRetry(1000, 3)); try{ client.start(); String path = "/linshi"; //b. 创建临时节点 client.create().withMode(CreateMode.EPHEMERAL).forPath(path, "hello".getBytes()); byte[] buf = client.getData().forPath(path); System.out.println("get data path:"+path+", data:"+new String(buf)); //Zookeeper创建临时节点的时候，不能创建级联的节点，下面的create会报错 String path2 = "/linshi/test"; //b. 创建临时节点 client.create().withMode(CreateMode.EPHEMERAL).forPath(path2, "hello".getBytes()); //byte[] buf2 = client.getData().forPath(path2); //System.out.println("get data path:"+path2+", data:"+new String(buf2)); TimeUnit.SECONDS.sleep(100 * 1000); }finally { if(client!=null) client.close(); } }
示例三：3、临时节点何时失效演示（在会话结束时被移除）
/** * 临时节点什么时候失效？是在本次会话结束时 * @throws Exception */ public static void test3() throws Exception { String address = "localhost:2181"; CuratorFramework client = CuratorFrameworkFactory.newClient(address, new ExponentialBackoffRetry(1000, 3)); try{ client.start(); String path = "/linshi"; //b. 创建临时节点 client.create().withMode(CreateMode.EPHEMERAL).forPath(path, "hello".getBytes()); byte[] buf = client.getData().forPath(path); System.out.println("get data path:"+path+", data:"+new String(buf)); TimeUnit.SECONDS.sleep(100 * 1000); }finally { if(client!=null) client.close(); } }
