连接测试

import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class ZKEnvTest {
    public static void main(String[] args) throws Exception{
        // 参数1：连接的地址；参数2：会话超时时间；参数3：事件处理器
        ZooKeeper zk = new ZooKeeper("linux01:2181,linux02:2181,linux03:2181", 2000, null);
        Stat stat = zk.exists("/demo", false);

        if(stat == null){
            System.out.println("/demo 不存在");
        }else{
            System.out.println("/demo 存在");
        }
        zk.close();
    }
}

数据操作

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.util.List;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class DataDemo {

    ZooKeeper zk = null;

    @Before
    public void init() throws Exception {
        zk = new ZooKeeper("linux01:2181,linux02:2181,linux03:2181", 2000, null);
    }

    // 创建znode
    @Test
    public void testCreate() throws Exception {

        // ByteArrayOutputStream数据不在文件里，而是在内存里
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        DataOutputStream dout = new DataOutputStream(bout);
        dout.writeInt(1288);

        byte[] data = bout.toByteArray();

        // zk.create(path,data,acl,createMode)
        // 参数1：路径；参数2：值；参数3：权限；参数4：创建模式；返回值：路径（+序号）
        String s = zk.create("/demo", data, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

        System.out.println(s);
    }

    // 获取znode的value数据
    @Test
    public void getData() throws Exception {

        // zk.getData(path,watch,stat)
        // 参数1：路径；参数2：是否注册监听；参数3：元数据（指定版本）
        byte[] data = zk.getData("/demo", false, null);

        ByteArrayInputStream bin = new ByteArrayInputStream(data);
        DataInputStream din = new DataInputStream(bin);

        int value = din.readInt();
        System.out.println(value);
    }

    // 获取指定路径下的子节点
    @Test
    public void getChildren() throws Exception {

        // zk.getChildren(path,watch)
        // 参数1：路径；参数2：是否注册监听
        List<String> lst = zk.getChildren("/", null);
        System.out.println(lst);

    }

    // 修改一个节点的value值
    @Test
    public void setData() throws Exception {

        // zk.setData(path,data,version)
        // 参数1：路径；参数2：值；参数3：版本（-1：更改所有版本）
        zk.setData("/demo", "字符串".getBytes(), -1);

        byte[] data = zk.getData("/demo", false, null);
        String s = new String(data);
        System.out.println(s);
    }

    // 删除一个znode
    @Test
    public void deleteNode() throws Exception {

        // zk.delete(path,version);
        // 参数1：路径；参数23：版本（-1：删除所有版本）
        zk.delete("/demo", -1);

        // Directory not empty for /demo若有子节点无法删除, rmr可以删除
    }

    @After
    public void close() throws Exception {
        zk.close();
    }

}

递归删除有子节点的节点

import java.util.List;

import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class RecursiveDelete {

    public static void main(String[] args) throws Exception {
        recursiveDelete("/demo");
    }

    public static void recursiveDelete(String path) throws Exception	{

        ZooKeeper zk = new ZooKeeper("linux01:2181,linux02:2181,linux03:2181", 2000, null);

        List<String> children = zk.getChildren(path, false);
        for (String string : children) {
            Stat stat = zk.exists(path + "/" + string, null);
            if(stat != null) {
                recursiveDelete(path + "/" + string);
            }
        }

        zk.delete(path, -1);

        zk.close();

    }
}

注册监听

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.junit.Before;
import org.junit.Test;

public class WatchDemo {

    ZooKeeper zk = null;

    @Before
    public void init() throws Exception {

        zk = new ZooKeeper("linux01:2181,linux02:2181,linux03:2181", 2000, new Watcher() {

            @Override
            public void process(WatchedEvent event) {// 连接一旦成功，方法会被调用一次
                System.out.println(event.getPath());// 事件发生的节点路径
                System.out.println(event.getState());// 事件发生时，客户端的连接状态
                System.out.println(event.getType());// 事件的类型
            }
        });
    }


    // 方式1：在注册监听时，传入boolean参数，事件的回调逻辑使用构造zk客户端时传入的回调逻辑
    // 监听节点的value变化事件
    @Test
    public void testWatchDataChanged() throws Exception {

        byte[] data = zk.getData("/demo", true, null);
        // zk对象是一个多线程的工作逻辑，对事件的监听是开启了一个另外的线程在工作

        Thread.sleep(Long.MAX_VALUE);
    }

    // 方式2：在注册监听时，传入Watcher对象，事件的回调逻辑使用此传入的Watcher
    @Test
    public void testWatchDataChanged2() throws Exception {

        byte[] data = zk.getData("/demo", new Watcher() {

            @Override
            public void process(WatchedEvent event) {

                System.out.println("处理事件");
            }
        }, null);

        Thread.sleep(Long.MAX_VALUE);
    }

    // 监听节点的子节点增减事件
    @Test
    public void TestWatchChildrenChanged() throws Exception {

        zk.getChildren("/demo", true);
        Thread.sleep(Long.MAX_VALUE);
    }

    // 监听节点被创建或被删除事件
    @Test
    public void testWatchStat() throws Exception {

        zk.exists("/demo", true);
        Thread.sleep(Long.MAX_VALUE);
    }

}

持续监听

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.junit.Before;
import org.junit.Test;

public class ContinueWatch {
	
	ZooKeeper zk = null;
	
	@Before
	public void init() throws Exception {
		zk = new ZooKeeper("linux01:2181,linux02:2181,linux03:2181", 2000, new Watcher() {
			@Override
			public void process(WatchedEvent event) {
				if(event.getType() == Event.EventType.NodeDataChanged) {
					try {
						// 处理事件
						System.out.println(event.getPath() + "-->" +event.getType());
						// 重新注册监听
						zk.getData("/demo", true, null);
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			}
		});
	}
	
	@Test
	public void continueWatch() throws Exception {
		zk.getData("/demo", true, null);
		Thread.sleep(Long.MAX_VALUE);
	}
}

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.junit.Before;
import org.junit.Test;

public class ContinueWatch {
	
	ZooKeeper zk = null;
	
	@Before
	public void init() throws Exception {
		zk = new ZooKeeper("linux01:2181,linux02:2181,linux03:2181", 2000, null);
	}
	
	@Test
	public void continueWatch() throws Exception {
		zk.getData("/demo", new Watcher() {
			@Override
			public void process(WatchedEvent event) {
				
				try {
					System.out.println(event.getPath() + "-->" +event.getType());
					zk.getData("/demo", this, null);
				} catch (KeeperException | InterruptedException e) {
					e.printStackTrace();
				}
			}
		}, null);
		
		Thread.sleep(Long.MAX_VALUE);
	}
}

Zookeeper的API使用