1 注册中心的原理

2 环境准备

需要一台linux
linux安装zookeeper，教程详情
https://blog.csdn.net/qq_41520636/article/details/114959972

3 下载ZooInspector可视化工具

下载地址： https://issues.apache.org/jira/secure/attachment/12436620/ZooInspector.zip
Zookeeper之ZKClient入门 - 图3

双击zookeeper-dev-ZooInspector.jar打开
Zookeeper之ZKClient入门 - 图4

输入ip和过期时间
Zookeeper之ZKClient入门 - 图5

建立连接，里面的dubbo是我前面练习产生的数据，如果没有使用过zookeeper，那么服务地址只有zookeeper这个文件目录。

Zookeeper之ZKClient入门 - 图6

4 ZKClient的使用

导入pom.xml

        <dependency>
            <groupId>com.101tec</groupId>
            <artifactId>zkclient</artifactId>
            <version>0.11</version>
        </dependency>

注意：在注册中心的服务地址是唯一的，不能重复创建。

4.1 创建持久化节点

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        // 创建会话
        ZkClient zkClient = new ZkClient(ZKServer);
        //    1.创建持久化节点（创建后，即便客户端与服务端断开连接，该节点依然存在）
        zkClient.createPersistent("/http");
    }
}

结果

23:44:47.104 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df001b, packet:: clientPath:null serverPath:null finished:false header:: 1,1 replyHeader:: 1,95,0 request:: ‘/http,,v{s{31,s{‘world,’anyone}}},0 response:: ‘/http

Zookeeper之ZKClient入门 - 图7

4.2 创建普通节点

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        // 创建会话
        ZkClient zkClient = new ZkClient(ZKServer);
        String s = zkClient.create(uri, "/dubbo/123", CreateMode.EPHEMERAL);
    }
}

结果

23:50:22.145 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df001c, packet:: clientPath:null serverPath:null finished:false header:: 1,1 replyHeader:: 1,98,0 request:: ‘/dubbo/com.hikktn.service.TestService,#ffffffacffffffed05740a2f647562626f2f313233,v{s{31,s{‘world,’anyone}}},1 response:: ‘/dubbo/com.hikktn.service.TestService

Zookeeper之ZKClient入门 - 图8
几秒钟后，数据已经失效

Zookeeper之ZKClient入门 - 图9

4.3 创建临时节点

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        // 创建会话
        ZkClient zkClient = new ZkClient(ZKServer);
        zkClient.createEphemeral("/dubbo/localhost:8888");
    }
}

结果

00:03:14.657 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df001e, packet:: clientPath:null serverPath:null finished:false header:: 1,1 replyHeader:: 1,104,0 request:: ‘/dubbo/localhost:8888,,v{s{31,s{‘world,’anyone}}},1 response:: ‘/dubbo/localhost:8888

也会在几秒钟后失效。

Zookeeper之ZKClient入门 - 图10

4.4 创建普通节点-写入序列化对象数据

import java.io.Serializable;
public class User implements Serializable {
    private Integer id;
    private String name;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        // 创建会话
        ZkClient zkClient = new ZkClient(ZKServer,10000,10000,new SerializableSerializer());
        User user =new User();
        user.setId(1);
        user.setName("张三");
        String path = zkClient.create("/dubbo/com.hikktn.service.TestService", user, CreateMode.PERSISTENT);
        System.out.println(path);
    }
}

结果

00:07:43.369 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df001f, packet:: clientPath:null serverPath:null finished:false header:: 1,1 replyHeader:: 1,107,0 request:: ‘/dubbo/com.hikktn.service.TestService,#ffffffacffffffed057372015636f6d2e68696b6b746e2e7574696c732e55736572ffffffa62b36ffffff8652ffffffdeffffffb0582024c026964740134c6a6176612f6c616e672f496e74656765723b4c046e616d65740124c6a6176612f6c616e672f537472696e673b787073720116a6176612e6c616e672e496e746567657212ffffffe2ffffffa0ffffffa4fffffff7ffffff81ffffff8738201490576616c756578720106a6176612e6c616e672e4e756d626572ffffff86ffffffacffffff951dbffffff94ffffffe0ffffff8b200787000017406ffffffe5ffffffbcffffffa0ffffffe4ffffffb8ffffff89,v{s{31,s{‘world,’anyone}}},0 response:: ‘/dubbo/com.hikktn.service.TestService

Zookeeper之ZKClient入门 - 图11

4.5 获取子节点内容

Zookeeper之ZKClient入门 - 图12

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        // 创建会话
        ZkClient zkClient = new ZkClient(ZKServer,5000,100000);
        List<String> children = zkClient.getChildren("/dubbo/localhost:8888");
        children.forEach((k) ->{
            System.out.println(k);
        });
    }
}

结果

00:28:21.647 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df0024, packet:: clientPath:null serverPath:null finished:false header:: 1,8 replyHeader:: 1,121,0 request:: ‘/dubbo/com.hikktn.service.TestService,F response:: v{‘localhost:8889,’localhost:8888}
localhost:8889
localhost:8888

4.6 获取序列化的内容

注意：必须是序列化的数据才能读取出来

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        ZkClient zkClient = new ZkClient(ZKServer,5000,100000,new SerializableSerializer());
        User user = zkClient.readData("/dubbo/com.hikktn.service.TestService");
        System.out.println(user.getId()+":"+user.getName());
    }
}

结果

00:33:21.553 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df0025, packet:: clientPath:null serverPath:null finished:false header:: 1,4 replyHeader:: 1,123,0 request:: ‘/dubbo/com.hikktn.service.TestService,F response:: #ffffffacffffffed057372015636f6d2e68696b6b746e2e7574696c732e55736572ffffffa62b36ffffff8652ffffffdeffffffb0582024c026964740134c6a6176612f6c616e672f496e74656765723b4c046e616d65740124c6a6176612f6c616e672f537472696e673b787073720116a6176612e6c616e672e496e746567657212ffffffe2ffffffa0ffffffa4fffffff7ffffff81ffffff8738201490576616c756578720106a6176612e6c616e672e4e756d626572ffffff86ffffffacffffff951dbffffff94ffffffe0ffffff8b200787000017406ffffffe5ffffffbcffffffa0ffffffe4ffffffb8ffffff89,s{107,107,1616170063293,1616170063293,0,2,0,0,183,2,110}
1:张三

4.7 订阅节点

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        ZkClient zkClient = new ZkClient(ZKServer,5000,100000,new SerializableSerializer());
        String uri ="/dubbo/com.hikktn.service.TestService";
        // 创建会话
        ZkClient zkClient = new ZkClient(zkServer,10000,10000,new SerializableSerializer());
        zkClient.subscribeChildChanges(uri, new IZkChildListener() {
            @Override
            public void handleChildChange(String parentPath, List<String> currentChilds) throws Exception {
                System.out.println("该节点里面有变化"+parentPath);
                System.out.println("该节点当前的子节点发生变化"+currentChilds);
            }
        });
        try {
            System.in.read();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

删除了节点：localhost:8888

Zookeeper之ZKClient入门 - 图13
结果

00:53:21.581 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df0028, packet:: clientPath:null serverPath:null finished:false header:: 3,3 replyHeader:: 3,132,0 request:: ‘/dubbo/com.hikktn.service.TestService,T response:: s{107,128,1616170063293,1616172655802,1,3,0,0,183,1,131}
00:53:21.584 [main-SendThread(192.168.135.20:2181)] DEBUG org.apache.zookeeper.ClientCnxn - Reading reply sessionid:0x100058112df0028, packet:: clientPath:null serverPath:null finished:false header:: 4,8 replyHeader:: 4,132,0 request:: ‘/dubbo/com.hikktn.service.TestService,T response:: v{‘localhost:8889}
该节点里面有变化/dubbo/com.hikktn.service.TestService
该节点当前的子节点发生变化[localhost:8889]

4.8 订阅节点内容出现变化

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        ZkClient zkClient = new ZkClient(ZKServer,5000,100000,new SerializableSerializer());
        String uri ="/dubbo/com.hikktn.service.TestService";
        // 创建会话
        ZkClient zkClient = new ZkClient(zkServer,10000,10000,new SerializableSerializer());
        zkClient.subscribeDataChanges(uri, new IZkDataListener() {
            @Override
            public void handleDataChange(String path, Object data) throws Exception {
                System.out.println("节点里面的数据发生变化的地址"+path);
                System.out.println("节点里面的数据发生变化具体内容"+data.toString());
            }
            @Override
            public void handleDataDeleted(String path) throws Exception {
                System.out.println("节点里面的数据被删除了"+path);
            }
        });
    }
}

4.9 更新和删除节点

public class ZKUtils {
    public static void main(String[] args) {
        // uri
        String ZKServer = "192.168.135.20:2181";
        ZkClient zkClient = new ZkClient(ZKServer,5000,100000,new SerializableSerializer());
        String uri ="/dubbo/com.hikktn.service.TestService";
        // 创建会话
        ZkClient zkClient = new ZkClient(zkServer,10000,10000,new SerializableSerializer());
        // 判断节点是否存在
        boolean exists = zkClient.exists(uri);
        if (exists){
            User user =new User();
            user.setId(2);
            user.setName("李四");
            // 写入节点（会直接覆盖）
            zkClient.writeData(uri,user);
        }else {
            // 删除节点
            zkClient.delete(uri);
            zkClient.deleteRecursive(uri);
        }
    }
}