Zookeeper API for JAVA实战与应用

package com.zookeeper.watcher;

import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.log4j.Logger;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Stat;

public class ZKClient implements Watcher{
private static final Logger logger = Logger.getLogger(ZKClient.class);

//定义session失效时间
private static final int SESSION_TIMEOUT = 10000;
//zookeeper服务器地址
private static final String ZOOKEEPER_ADDRESS = "192.168.56.1:2181";

//ZooKeeper变量
private ZooKeeper zk = null;
//定义原子变量
AtomicInteger seq = new AtomicInteger();
//信号量设置，用于等待zookeeper连接建立之后，通知阻塞程序继续向下执行
private CountDownLatch connectedSemaphore = new CountDownLatch(1);

public static void main(String[] args) throws InterruptedException {
String parentPath= "/test"; //父节点
String childrenPath = "/test/children"; //子节点

ZKClient test = new ZKClient();
//创建链接
test.createConnection();

boolean isSuccess = test.createNode(parentPath, "abc", Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
if (isSuccess) {
//读取数据
String result = test.getNodeData(parentPath, true);
logger.info("更新前数据：" + result);

//更新数据
isSuccess = test.updateNode(parentPath, String.valueOf(System.currentTimeMillis()));
if(isSuccess){
logger.info("更新后数据：" + test.getNodeData(parentPath, true));
}

// 创建子节点
isSuccess = test.createNode(childrenPath, String.valueOf(System.currentTimeMillis()), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
if(isSuccess){
test.updateNode(childrenPath, String.valueOf(System.currentTimeMillis()));
}

//读取子节点
List<String> childrenList = test.getChildren(parentPath, true);
if(childrenList!=null && !childrenList.isEmpty()){
for(String children : childrenList){
System.out.println("子节点：" + children);
}
}
}

Thread.sleep(1000);
//创建临时有序子节点
test.createNode(childrenPath, String.valueOf(System.currentTimeMillis()), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
test.createNode(childrenPath, String.valueOf(System.currentTimeMillis()), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
test.createNode(childrenPath, String.valueOf(System.currentTimeMillis()), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);

// 读取子节点，并删除
List<String> childrenList = test.getChildren(parentPath, true);
if (childrenList != null && !childrenList.isEmpty()) {
for (String children : childrenList) {
System.out.println("子节点：" + children);
test.deleteNode(parentPath + "/" + children);
}
}

//删除父节点
if (test.exists(childrenPath, false) != null) {
test.deleteNode(childrenPath);
}

//释放链接
Thread.sleep(1000);
test.releaseConnection();
}

/**
* 创建节点
*
* @param path 节点路径
* @param data 数据内容
* @param acl 访问控制列表
* @param createMode znode创建类型
* @return
*/
public boolean createNode(String path, String data, List<ACL> acl, CreateMode createMode) {
try {
//设置监控(由于zookeeper的监控都是一次性的，所以每次必须设置监控)
exists(path, true);
String resultPath = this.zk.create(path, data.getBytes(), acl, createMode);
logger.info(String.format("节点创建成功，path: %s，data: %s", resultPath, data));
} catch (Exception e) {
logger.error("节点创建失败", e);
return false;
}

return true;
}

/**
* 更新指定节点数据内容
*
* @param path 节点路径
* @param data 数据内容
* @return
*/
public boolean updateNode(String path, String data) {
try {
Stat stat = this.zk.setData(path, data.getBytes(), -1);
logger.info("更新节点数据成功，path：" + path + ", stat: " + stat);
} catch (Exception e) {
logger.error("更新节点数据失败", e);
return false;
}

return true;
}

/**
* 删除指定节点
*
* @param path
*            节点path
*/
public void deleteNode(String path) {
try {
this.zk.delete(path, -1);
logger.info("删除节点成功，path：" + path);
} catch (Exception e) {
logger.error("删除节点失败", e);
}
}

/**
* 读取节点数据
*
* @param path 节点路径
* @param needWatch 是否监控这个目录节点，这里的 watcher是在创建ZooKeeper实例时指定的watcher
* @return
*/
public String getNodeData(String path, boolean needWatch) {
try {
Stat stat = exists(path, needWatch);
if(stat != null){
return new String(this.zk.getData(path, needWatch, stat));
}
} catch (Exception e) {
logger.error("读取节点数据内容失败", e);
}

return null;
}

/**
* 获取子节点
*
* @param path 节点路径
* @param needWatch  是否监控这个目录节点，这里的 watcher是在创建ZooKeeper实例时指定的watcher
* @return
*/
public List<String> getChildren(String path, boolean needWatch) {
try {
return this.zk.getChildren(path, needWatch);
} catch (Exception e) {
logger.error("获取子节点失败", e);
return null;
}
}

/**
* 判断znode节点是否存在
*
* @param path 节点路径
* @param needWatch 是否监控这个目录节点，这里的 watcher是在创建ZooKeeper实例时指定的watcher
* @return
*/
public Stat exists(String path, boolean needWatch) {
try {
return this.zk.exists(path, needWatch);
} catch (Exception e) {
logger.error("判断znode节点是否存在发生异常", e);
}

return null;
}

/**
* 创建ZK连接
*
* @param connectAddr
* @param sessionTimeout
*/
public void createConnection() {
this.releaseConnection();

try {
zk = new ZooKeeper(ZOOKEEPER_ADDRESS, SESSION_TIMEOUT, this);
logger.info("开始连接ZK服务器...");

//zk连接未创建成功进行阻塞
connectedSemaphore.await();
} catch (Exception e) {
logger.error("ZK连接创建失败", e);
}
}

/**
* 关闭ZK连接
*/
public void releaseConnection() {
if (this.zk != null) {
try {
this.zk.close();
logger.info("ZK连接关闭成功");
} catch (InterruptedException e) {
logger.error("ZK连接关闭失败", e);
}
}
}

@Override
public void process(WatchedEvent event) {
logger.info("进入process()方法...event = " + event);

if (event == null) {
return;
}

KeeperState keeperState = event.getState(); // 连接状态
EventType eventType = event.getType(); // 事件类型
String path = event.getPath(); // 受影响的path

String logPrefix = "【Watcher-" + this.seq.incrementAndGet() + "】";
logger.info(String.format("%s收到Watcher通知...", logPrefix));
logger.info(String.format("%s连接状态：%s", logPrefix, keeperState));
logger.info(String.format("%s事件类型：%s", logPrefix, eventType));
logger.info(String.format("%s受影响的path：%s", logPrefix, path));

if (KeeperState.SyncConnected == keeperState) {
if (EventType.None == eventType) {
// 成功连接上ZK服务器
logger.info(logPrefix + "成功连接上ZK服务器...");
connectedSemaphore.countDown();

} else if (EventType.NodeCreated == eventType) {
// 创建节点
logger.info(logPrefix + "节点创建");
this.exists(path, true);

} else if (EventType.NodeDataChanged == eventType) {
// 更新节点
logger.info(logPrefix + "节点数据更新");
logger.info(logPrefix + "数据内容: " + this.getNodeData(path, true));

} else if (EventType.NodeChildrenChanged == eventType) {
// 更新子节点
logger.info(logPrefix + "子节点变更");
logger.info(logPrefix + "子节点列表：" + this.getChildren(path, true));

} else if (EventType.NodeDeleted == eventType) {
// 删除节点
logger.info(logPrefix + "节点 " + path + " 被删除");
}

} else if (KeeperState.Disconnected == keeperState) {
logger.info(logPrefix + "与ZK服务器断开连接");
} else if (KeeperState.AuthFailed == keeperState) {
logger.info(logPrefix + "权限检查失败");
} else if (KeeperState.Expired == keeperState) {
logger.info(logPrefix + "会话失效");
}

}

}