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：

    <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

    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

        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

        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）：

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　

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

5.删除节点

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

　删除包含子节点的节点

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

6.查询节点

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

读取属性：

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 

//  /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

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