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一、简介

Zookeeper 可作为注册中心，实现服务注册与发现，当服务启动后，就会注册到 Zookeeper，然后保存该服务的地址以以及一些基本的信息，其他服务可从注册中心获取到该服务的地址，进行 RPC 远程调用，和 Eureka 作为注册中心同理，Eureka 和 Zookeeper 的区别在于 Eureka 保证 AP，也就是保证高可用和分区容错，Zookeeper 保证 CP，也就是保证一致性和分区容错。

二、实例

1、创建 SpringBoot 项目添加依赖

   			
    
     org.springframework.boot
    			
    
     spring-boot-starter-web
    			
    				
     					
      
       org.springframework.boot
      					
      
       spring-boot-starter-logging
      				
     			
    		
   		
   			
    
     com.101tec
    			
    
     zkclient
    			
    
     0.8
    		
   	

2、编写服务注册代码

编写一个类实现 ApplicationRunner 接口，然后注册到 Spring 容器中，当我们启动 Spring 项目后，就会执行以下代码把该服务注册到 Zookeeper，我们可以修改 yml 配置文件中的端口号，分别注册多个实例。

@Componentpublic class MyApplicationRunner implements ApplicationRunner {
       @Value("${server.port}")    private String port;    private static CountDownLatch countDownLatch = new CountDownLatch(1);    @Override    public void run(ApplicationArguments args) throws Exception {
           ZooKeeper zooKeeper = new ZooKeeper("10.13.1.171:2181", 5000, new Watcher() {
               @Override            public void process(WatchedEvent watchedEvent) {
                   //获取连接状态                Event.KeeperState state = watchedEvent.getState();                if (state == Event.KeeperState.SyncConnected) {
                       System.out.println("zk连接成功");                    countDownLatch.countDown();                }            }        });        countDownLatch.await();        String parentPath = "/user-service";        Stat exits = zooKeeper.exists(parentPath, null);        if (exits == null) {
               zooKeeper.create(parentPath,"user".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);        }        String path = "http://127.0.0.1"+port;        zooKeeper.create(parentPath+"/"+port,path.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);        System.out.println("服务注册成功！");    }}

3、编写服务发现代码

public class ZkTest {
       //计数器    private static CountDownLatch countDownLatch = new CountDownLatch(1);    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
           /**         * 1、连接地址         * 2、超时时间         * 3、事件通知         */        ZooKeeper zooKeeper = new ZooKeeper("10.13.1.171:2181", 5000, new Watcher() {
               @Override            public void process(WatchedEvent watchedEvent) {
                   //获取连接状态                Event.KeeperState state = watchedEvent.getState();                if (state == Event.KeeperState.SyncConnected) {
                       System.out.println("zk连接成功");                    countDownLatch.countDown();                }            }        });        countDownLatch.await();        String path = "/user-service";        List
   
     children = zooKeeper.getChildren(path, null, new Stat());        for (int i = 0; i < children.size(); i++) {
               String pathChildren = path + "/" + children.get(i);            byte[] data = zooKeeper.getData(pathChildren, null, new Stat());            System.out.println("服务地址：" + new String(data));        }    }}
   

四、代码下载

https://github.com/huangliangyun/Spring-Boot-2.X/tree/master/spring-boot-zookeeper

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