【ZooKeeper Notes 3】ZooKeeper Java API 使用样例

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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，关于ZooKeeper的典型使用场景，请查看这个文章《ZooKeeper典型使用场景一览》

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<br>  * ZK Api Version: 3.4.3   */ 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();         }      }  }

输出结果：

收到事件通知：SyncConnected  节点创建成功, Path: /nileader, content: 我是节点初始内容  获取数据成功，path：/nileader 数据内容: 我是节点初始内容  更新数据成功，path：/nileader, stat: 42950186407,42950186408,1350820182392,1350820182406,1,0,0,232029990722229433,18,0,42950186407  获取数据成功，path：/nileader 数据内容: 更新后的数据  删除节点成功，path：/nileader

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