众所周知，ZooKeeper中的ZNode是树形结构，现在我需要给/app1结点设置watcher，监听/app1下增减、删除和修改的结点，并将相应的事件使用log4j记录到日志文件中。ZNode的变化可以直接通过event.getType来获取。使用zk.exists(PATH, wc);来为PATH结点设置watcher，所有结点都可以使用wc做watcher。
代码如下：
package com.iflytek.cpcloud.zookeeper; import java.io.IOException;
import java.util.List; import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.log4j.PropertyConfigurator;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.Watcher.Event.EventType; public class WatchClient implements Runnable { private static final Log LOG = LogFactory.getLog(WatchClient.class);
public static final int CLIENT_PORT = 2181;
public static final String PATH = "/app1";// 所要监控的结点
private static ZooKeeper zk;
private static List<String> nodeList;// 所要监控的结点的子结点列表 public static void main(String[] args) throws Exception {
PropertyConfigurator.configure("F:\\test\\conf\\log4j.properties");
WatchClient client = new WatchClient();
Thread th = new Thread(client);
th.start();
} public WatchClient() throws IOException { zk = new ZooKeeper("192.168.255.133:" + CLIENT_PORT, 21810,
new Watcher() {
public void process(WatchedEvent event) {
}
});
} /**
* 设置watch的线程
*/
@Override
public void run() { Watcher wc = new Watcher() {
@Override
public void process(WatchedEvent event) {
// 结点数据改变之前的结点列表
List<String> nodeListBefore = nodeList;
// 主结点的数据发生改变时
if (event.getType() == EventType.NodeDataChanged) {
LOG.info("Node data changed:" + event.getPath());
}
if (event.getType() == EventType.NodeDeleted){
LOG.info("Node deleted:" + event.getPath());
}
if(event.getType()== EventType.NodeCreated){
LOG.info("Node created:"+event.getPath());
} // 获取更新后的nodelist
try {
nodeList = zk.getChildren(event.getPath(), false);
} catch (KeeperException e) {
System.out.println(event.getPath()+" has no child, deleted.");
} catch (InterruptedException e) {
e.printStackTrace();
}
List<String> nodeListNow = nodeList;
// 增加结点
if (nodeListBefore.size() < nodeListNow.size()) {
for (String str : nodeListNow) {
if (!nodeListBefore.contains(str)) {
LOG.info("Node created:" + event.getPath() + "/" + str);
}
}
}
}
}; /**
* 持续监控PATH下的结点
*/
while (true) {
try {
zk.exists(PATH, wc);//所要监控的主结点
} catch (KeeperException | InterruptedException e) {
e.printStackTrace();
}
try {
nodeList = zk.getChildren(PATH, wc);
} catch (KeeperException | InterruptedException e) {
e.printStackTrace();
}
// 对PATH下的每个结点都设置一个watcher for (String nodeName : nodeList) {
try {
zk.exists(PATH + "/" + nodeName, wc);
} catch (KeeperException | InterruptedException e) {
e.printStackTrace();
}
} try {
Thread.sleep(3000);// sleep一会，减少CUP占用率
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
该项目使用maven构建。pom.xml文件如下：
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.iflytek.cpcloud</groupId>
<artifactId>zookeeper-test</artifactId>
<version>0.1.0-SNAPSHOT</version> <dependencies>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.1.1</version>
</dependency>
<dependency>
<groupId>commons-cli</groupId>
<artifactId>commons-cli</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
</dependency>
<dependency>
<groupId>org.apache.zookeeper</groupId>
<artifactId>zookeeper</artifactId>
<version>3.4.5</version>
</dependency>
</dependencies> <build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2-beta-5</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build> </project>