中间件 ZK分布式专题与Dubbo微服务入门 6-9 获取zk子节点列表

0　　　　课程地址

https://coding.imooc.com/lesson/201.html#mid=12725

 

1　　　　重点关注

1.1　　　　本节内容

获取zk子节点数据demo，有其余一些比较简单的demo没有演练，用到这块的话，也可以再看下视频

 

1.2　　　　关键代码

    public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
        for (String s : children) {
            System.out.println(s);
        }
        System.out.println("ChildrenCallback:" + path);
        System.out.println((String)ctx);    
        System.out.println(stat.toString());
    }

 

2　　　　课程内容

2.1　　　　额外学习之byte转String方法

                byte[] resByte = zkServer.getZookeeper().getData("/imooc", false, stat);
                String result = new String(resByte);

 

 

 

3　　　　Coding

3.1　　　　获取zk节点数据

• 启动服务端

    进入到
cd /usr/local/zookeeper/bin

 
    重启zookeeper服务端
./zkServer.sh restart

 

• 主类

package com.imooc.zk.demo;

import java.io.IOException;
import java.util.List;
import java.util.concurrent.CountDownLatch;

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;

/**
 * @Description: zookeeper 获取子节点数据的demo演示
 */
public class ZKGetChildrenList implements Watcher {

    private ZooKeeper zookeeper = null;
    
    public static final String zkServerPath = "172.26.139.4:2181";
    public static final Integer timeout = 5000;
    
    public ZKGetChildrenList() {}
    
    public ZKGetChildrenList(String connectString) {
        try {
            zookeeper = new ZooKeeper(connectString, timeout, new ZKGetChildrenList());
        } catch (IOException e) {
            e.printStackTrace();
            if (zookeeper != null) {
                try {
                    zookeeper.close();
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }
    
    private static CountDownLatch countDown = new CountDownLatch(1);
    
    public static void main(String[] args) throws Exception {
    
        ZKGetChildrenList zkServer = new ZKGetChildrenList(zkServerPath);
        
        /**
         * 参数：
         * path：父节点路径
         * watch：true或者false，注册一个watch事件
         */
//        List<String> strChildList = zkServer.getZookeeper().getChildren("/imooc", true);
//        for (String s : strChildList) {
//            System.out.println(s);
//        }
        
        // 异步调用
        String ctx = "{'callback':'ChildrenCallback'}";
        zkServer.getZookeeper().getChildren("/imooc", true, new Children2CallBack(), ctx);
        
        countDown.await();
    }
    
    @Override
    public void process(WatchedEvent event) {
        try {
            if(event.getType()==EventType.NodeChildrenChanged){
                System.out.println("NodeChildrenChanged");
                ZKGetChildrenList zkServer = new ZKGetChildrenList(zkServerPath);
                List<String> strChildList = zkServer.getZookeeper().getChildren(event.getPath(), false);
                for (String s : strChildList) {
                    System.out.println(s);
                }
                countDown.countDown();
            } else if(event.getType() == EventType.NodeCreated) {
                System.out.println("NodeCreated");
            } else if(event.getType() == EventType.NodeDataChanged) {
                System.out.println("NodeDataChanged");
            } else if(event.getType() == EventType.NodeDeleted) {
                System.out.println("NodeDeleted");
            } 
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public ZooKeeper getZookeeper() {
        return zookeeper;
    }
    public void setZookeeper(ZooKeeper zookeeper) {
        this.zookeeper = zookeeper;
    }
    
}

 

• 回调类：

package com.imooc.zk.demo;


import java.util.List;

import org.apache.zookeeper.AsyncCallback.Children2Callback;
import org.apache.zookeeper.data.Stat;

public class Children2CallBack implements Children2Callback {

    @Override
    public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
        for (String s : children) {
            System.out.println(s);
        }
        System.out.println("ChildrenCallback:" + path);
        System.out.println((String)ctx);    
        System.out.println(stat.toString());
    }


}

 

• 打印日志

aaa
abc
ChildrenCallback:/imooc
{'callback':'ChildrenCallback'}
25,147,1704774619142,1712011283195,2,8,0,0,3,2,50

 

• linux客户端更新数据

--启动客户端
zkCli.sh

[zk: localhost:2181(CONNECTED) 0] ls /
[imooc2, names, zookeeper, imooc3, imooc, testnode, imooc5]

--查看节点imooc
[zk: localhost:2181(CONNECTED) 3] get /imooc
520
cZxid = 0x19
ctime = Tue Jan 09 12:30:19 CST 2024
mZxid = 0x93
mtime = Tue Apr 02 06:41:23 CST 2024
pZxid = 0x32
cversion = 8
dataVersion = 2
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 3
numChildren = 2

 

• 验证：

linux客户端标红部分和日志打印部分能对应上，时间转化后也可以看下