java

关注公众号 jb51net

关闭
首页 > 软件编程 > java > java连接zookeeper

java连接zookeeper的实现示例

作者：曹朋羽

ZooKeeper官方提供了Java API,可以通过Java代码来连接zookeeper服务进行操作,本文就来介绍一下java连接zookeeper的实现示例,具有一定的参考价值,感兴趣的可以了解一下

API

ZooKeeper官方提供了Java API，可以通过Java代码来连接zookeeper服务进行操作。可以连接、创建节点、获取节点数据、监听节点变化等操作，具体有以下几个重要的类：

添加依赖

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.7.2</version>
</dependency>

操作例子

String host = "localhost:2181";
//建立连接
zooKeeper = new ZooKeeper(host, 2000, null);
String path = "/test";
Watcher watcher = new Watcher() {
  @Override
  public void process(WatchedEvent watchedEvent) {
    System.out.println("Node changed: " + watchedEvent.getPath());
    System.out.println(watchedEvent);
  }
};
//获取节点状态 如果不存在返回null
Stat stat = zooKeeper.exists(path, false);
if(null != stat){
	System.out.println(stat.getCzxid()+"-"+stat.getAversion());
}

//创建节点 包含版本、时间、数据长度等信息
zooKeeper.create(path,"123".getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
//添加watcher
zooKeeper.addWatch(path, watcher, AddWatchMode.PERSISTENT);

//获取节点数据
byte[] data = zooKeeper.getData(path, false, null);
System.out.println(new String(data));

zooKeeper.create(path+"/1","child1".getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
//获取子节点
List<String> children = zooKeeper.getChildren(path, false);
System.out.println("childs size:"+children.size());
//删除子节点
zooKeeper.delete(path+"/1",-1);
zooKeeper.close();

zkClient

zkClient封装了zookeeper的官方api，简化了一些繁琐的操作，并提供了一些额外的功能，提高了开发效.

添加依赖

<dependency>
    <groupId>com.101tec</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.11</version>
</dependency>

zkclient对节点数据的操作进行了序列化， 这里先准备一个string类型的序列化类。需要实现ZkSerializer接口

public class ZkStringSerializer implements ZkSerializer {
    @Override
    public byte[] serialize(Object o) throws ZkMarshallingError {
        return String.valueOf(o).getBytes();
    }

    @Override
    public Object deserialize(byte[] bytes) throws ZkMarshallingError {
        return new String(bytes);
    }
}

基本操作

ZkClient zkClient = new ZkClient("localhost:2181");
//自定义序列化 否则报错
zkClient.setZkSerializer(new ZkStringSerializer());
String path = "/test";
//判断节点是否存在
boolean exist = zkClient.exists(path);
System.out.println(exist);
if(!exist){//创建节点
    zkClient.create(path,"123", CreateMode.PERSISTENT);
}
//读取节点数据
System.out.println((String) zkClient.readData(path));
zkClient.writeData(path,"456");//设置节点数据
System.out.println((String) zkClient.readData(path));
zkClient.delete(path);//删除节点

zkClient.close();

节点变化事件

String path = "/test";
/**
 * 节点变化事件
 * 只监听节点增减，不监听数据变化事件
 */
zkClient.subscribeChildChanges(path, new IZkChildListener() {
    @Override
    public void handleChildChange(String parentPath, List<String> children) throws Exception {
        System.out.println("节点"+parentPath+"发生变化");
        System.out.println(children);
    }
});
//节点操作，观察handleChildChange接收到对应事件
Thread.sleep(2000);
zkClient.createPersistent(path);
Thread.sleep(2000);
zkClient.createPersistent(path+"/child1");
Thread.sleep(2000);
zkClient.writeData(path+"/child1","123");
Thread.sleep(2000);
zkClient.delete(path+"/child1");
Thread.sleep(2000);
zkClient.delete(path);
Thread.sleep(100000);

节点数据变化事件

    String path = "/test";
    /**
     * 节点变化事件,只检测当前节点，感知不到其子节点
     * 节点被删除或节点数据变化
     */
    zkClient.subscribeDataChanges(path, new IZkDataListener() {
        @Override
        public void handleDataChange(String s, Object o) throws Exception {
            System.out.println("节点："+s+"数据变为:"+o);
        }

        @Override
        public void handleDataDeleted(String s) throws Exception {
            System.out.println("节点："+s+"删除");
        }
    });

    Thread.sleep(2000);
    zkClient.createPersistent(path);
    Thread.sleep(2000);
    zkClient.createPersistent(path+"/child1");
    Thread.sleep(2000);
    zkClient.delete(path+"/child1");
    Thread.sleep(2000);
    zkClient.writeData(path,"123");
    Thread.sleep(2000);
    zkClient.delete(path);
    Thread.sleep(100000);
}

Curator

curator是另一个java连接zookeeper类库。功能更加强大。提供了连接重试、分布式锁、选举、队列等多种实际场景的用例。这里先简单搞个使用例子。

添加依赖

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>5.1.0</version>
</dependency>

curator-framework是基础的依赖，一些特定的使用方式需要添加不同的依赖，有curator-recipes、curator-x-discovery、curator-x-async等。

基本操作

//创建连接
CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", new ExponentialBackoffRetry(1000, 3));
client.start();
String path = "/test";
client.checkExists().forPath(path);//判断是否存在
client.create().forPath(path, "123".getBytes());//创建节点
byte[] data = client.getData().forPath(path);//获取数据
System.out.println(new String(data));
client.setData().forPath(path, "456".getBytes());//设置数据
client.delete().forPath(path);//删除节点

client.close();

节点监听

CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", new ExponentialBackoffRetry(1000, 3));
client.start();
String path = "/test";
NodeCache  nodeCache = new NodeCache(client,path);
//添加监听
nodeCache.getListenable().addListener(new NodeCacheListener() {
    @Override
    public void nodeChanged() throws Exception {
        ChildData data = nodeCache.getCurrentData();
        if (data != null) {
            System.out.println("Node changed: " + data.getPath() + ", value: " + new String(data.getData()));
        } else {
            System.out.println("Node deleted: " + nodeCache.getPath());
        }
    }
});
nodeCache.start();
client.create().forPath(path);
client.setData().forPath(path, "123".getBytes());
client.delete().forPath(path);
client.close();

这里NodeCache被标识@Deprecated，也不知道被什么方式代替了，后面再研究。先简单使用。

到此这篇关于java连接zookeeper的实现示例的文章就介绍到这了,更多相关java连接zookeeper内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

您可能感兴趣的文章:
阅读全文