1.使用什么API可以创建ZK（ZooKeeper）连接？
2.如何关闭ZK（ZooKeeper）连接？
3.如何创建节点？
4.如何读取数据？
5.如何删除指定节点？
6.如何收到来自Server的Watcher通知后的处理？
ZooKeeper是一个分布式的，开放源码的分布式应用程序协调服务框架，包含一组简单的原语集合。通过这些原语言的组合使用，能够帮助我们解决更高层次的分布式问题。
本文主要针对ZooKeeper提供的Java API，通过实际代码讲述如何使用API。
package com.taobao.taokeeper.research.sample;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import common.toolkit.java.util.ObjectUtil;
/**
* ZooKeeper Java Api 使用样例
* ZK Api Version: 3.4.3
*
* @author nileader/nileader@gmail.com
*/
public class JavaApiSample implements Watcher {
private static final int SESSION_TIMEOUT = 10000;
private static final String CONNECTION_STRING = “test.zookeeper.connection_string:2181”;
private static final String ZK_PATH = “/nileader”;
private ZooKeeper zk = null;
private CountDownLatch connectedSemaphore = new CountDownLatch( 1 );
/**
* 创建ZK连接
* @param connectString ZK服务器地址列表
* @param sessionTimeout Session超时时间
*/
public void createConnection( String connectString, int sessionTimeout ) {
this.releaseConnection();
try {
zk = new ZooKeeper( connectString, sessionTimeout, this );
connectedSemaphore.await();
} catch ( InterruptedException e ) {
System.out.println( “连接创建失败，发生 InterruptedException” );
e.printStackTrace();
} catch ( IOException e ) {
System.out.println( “连接创建失败，发生 IOException” );
e.printStackTrace();
}
}
/**
* 关闭ZK连接
*/
public void releaseConnection() {
if ( !ObjectUtil.isBlank( this.zk ) ) {
try {
this.zk.close();
} catch ( InterruptedException e ) {
// ignore
e.printStackTrace();
}
}
}
/**
* 创建节点
* @param path 节点path
* @param data 初始数据内容
* @return
*/
public boolean createPath( String path, String data ) {
try {
System.out.println( “节点创建成功, Path: ”
+ this.zk.create( path, //
data.getBytes(), //
Ids.OPEN_ACL_UNSAFE, //
CreateMode.EPHEMERAL )
+ “, content: ” + data );
} catch ( KeeperException e ) {
System.out.println( “节点创建失败，发生KeeperException” );
e.printStackTrace();
} catch ( InterruptedException e ) {
System.out.println( “节点创建失败，发生 InterruptedException” );
e.printStackTrace();
}
return true;
}
/**
* 读取指定节点数据内容
* @param path 节点path
* @return
*/
public String readData( String path ) {
try {
System.out.println( “获取数据成功，path：” + path );
return new String( this.zk.getData( path, false, null ) );
} catch ( KeeperException e ) {
System.out.println( “读取数据失败，发生KeeperException，path: ” + path );
e.printStackTrace();
return “”;
} catch ( InterruptedException e ) {
System.out.println( “读取数据失败，发生 InterruptedException，path: ” + path );
e.printStackTrace();
return “”;
}
}
/**
* 更新指定节点数据内容
* @param path 节点path
* @param data 数据内容
* @return
*/
public boolean writeData( String path, String data ) {
try {
System.out.println( “更新数据成功，path：” + path + “, stat: ” +
this.zk.setData( path, data.getBytes(), -1 ) );
} catch ( KeeperException e ) {
System.out.println( “更新数据失败，发生KeeperException，path: ” + path );
e.printStackTrace();
} catch ( InterruptedException e ) {
System.out.println( “更新数据失败，发生 InterruptedException，path: ” + path );
e.printStackTrace();
}
return false;
}
/**
* 删除指定节点
* @param path 节点path
*/
public void deleteNode( String path ) {
try {
this.zk.delete( path, -1 );
System.out.println( “删除节点成功，path：” + path );
} catch ( KeeperException e ) {
System.out.println( “删除节点失败，发生KeeperException，path: ” + path );
e.printStackTrace();
} catch ( InterruptedException e ) {
System.out.println( “删除节点失败，发生 InterruptedException，path: ” + path );
e.printStackTrace();
}
}
public static void main( String[] args ) {
JavaApiSample sample = new JavaApiSample();
sample.createConnection( CONNECTION_STRING, SESSION_TIMEOUT );
if ( sample.createPath( ZK_PATH, “我是节点初始内容” ) ) {
System.out.println();
System.out.println( “数据内容: ” + sample.readData( ZK_PATH ) + “\n” );
sample.writeData( ZK_PATH, “更新后的数据” );
System.out.println( “数据内容: ” + sample.readData( ZK_PATH ) + “\n” );
sample.deleteNode( ZK_PATH );
}
sample.releaseConnection();
}
/**
* 收到来自Server的Watcher通知后的处理。
*/
@Override
public void process( WatchedEvent event ) {
System.out.println( “收到事件通知：” + event.getState() +”\n” );
if ( KeeperState.SyncConnected == event.getState() ) {
connectedSemaphore.countDown();
}
}
}
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