Zookeeper:Curator增删改查API

1.介绍

What is Curator?

Curator n ˈkyoor͝ˌātər: a keeper or custodian of a museum or other collection - A ZooKeeper Keeper.

Apache Curator is a Java/JVM client library for Apache ZooKeeper, a distributed coordination service. It includes a highlevel API framework and utilities to make using Apache ZooKeeper much easier and more reliable. It also includes recipes for common use cases and extensions such as service discovery and a Java 8 asynchronous DSL.

curator官网

2.连接对象创建

maven依赖：

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<dependencies>     <dependency>         <groupId>org.apache.zookeeper</groupId>         <artifactId>zookeeper</artifactId>         <version>3.4.10</version>     </dependency>     <dependency>         <groupId>org.apache.curator</groupId>         <artifactId>curator-recipes</artifactId>         <version>2.6.0</version>     </dependency>     <dependency>         <groupId>org.apache.curator</groupId>         <artifactId>curator-framework</artifactId>         <version>2.6.0</version>         <exclusions>             <exclusion>                 <groupId>org.apache.zookeeper</groupId>                 <artifactId>zookeeper</artifactId>             </exclusion>         </exclusions>     </dependency>     <dependency>         <groupId>junit</groupId>         <artifactId>junit</artifactId>         <version>4.7</version>         <scope>test</scope>     </dependency> </dependencies>

　连接对象创建的代码

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public static void main(String[] args) {     CuratorFramework ct = CuratorFrameworkFactory.builder()             //ip:端口             .connectString("192.168.10.132:2181,192.168.10.133:2181,192.168.10.135:2181")//连接集群             //超时时间             .sessionTimeoutMs(5000)             //连接断开5秒后，会进行一次重连             .retryPolicy(new RetryOneTime(5000))             //命名空间，该命名空间作为父节点             .namespace("ct").build();     //打开连接     ct.start();     //是否连接成功     System.out.println(ct.isStarted());     //关闭连接     ct.close(); }

重连策略：

RetryOneTime(int sleepMsBetweenRetry)：只重连一次

RetryNTimes(int n, int sleepMsBetweenRetries)：重连n次

RetryUntilElapsed(int maxElapsedTimeMs, int sleepMsBetweenRetries)：每sleepMsBetweenRetries毫秒重连一次，总等待时间超过maxElapsedTimeMs毫秒后停止重连

ExponentialBackoffRetry(int baseSleepTimeMs, int maxRetries)：重连maxRetries次，重连间隔基于baseSleepTimeMs计算
计算公式如下：baseSleepTimeMs*Math.max(1,random.nextInt(1<<(retryCount+1)))。

3.创建节点

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ct.create()         //节点类型         .withMode(CreateMode.PERSISTENT)         //节点权限         .withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)         //节点路径和数据         .forPath("/node1","node1".getBytes());

　支持递归创建节点

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ct.create()         //父节点不存在则创建         .creatingParentsIfNeeded()         //节点类型         .withMode(CreateMode.PERSISTENT)         //节点权限         .withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)         //节点路径和数据         .forPath("/node2/node2","node2".getBytes());

　异步方式创建（删除、更新、查询省略）：

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ct.create()         //父节点不存在则创建         .creatingParentsIfNeeded()         //节点类型         .withMode(CreateMode.PERSISTENT)         //节点权限         .withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)         //异步回调         .inBackground(new BackgroundCallback() {             public void processResult(CuratorFramework client, CuratorEvent event) throws Exception {                 System.out.println(event.getPath()+":"+event.getType());             }         })         //节点路径和数据         .forPath("node3","node3".getBytes());

4.更新节点　

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1	ct.setData().withVersion(-1).forPath("/node3","node33".getBytes());

5.删除节点

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1	ct.delete().withVersion(-1).forPath("/node3");

　删除包含子节点的节点

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//递归删除 ct.delete()          .deletingChildrenIfNeeded()          .withVersion(-1).forPath("/node2");

6.查询节点

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//查询 byte[] bytes = ct.getData().forPath("/node1"); System.out.println(new String(bytes));

读取属性：

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Stat stat = new Stat(); byte[] bytes = ct.getData()      .storingStatIn(stat).forPath("/node1"); System.out.println(new String(bytes)); System.out.println(stat);

7.查询子节点数据 

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//  /ct/node1/node2 List<String> list = ct.getChildren().forPath("/node1"); for (String s : list) {        System.out.println(s); }

8.判断节点是否存在

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1 2	//如果节点不存在，则返回值为null Stat stat = ct.checkExists().forPath("/node11");