使用 Zookeeper 的 Api 实现服务订阅

服务提供者

服务提供者中拷贝 Constants

服务提供者中拷贝 UserService

连接 Zk 集群

/***
     * 连接ZooKeeper集群
     */
    public ZooKeeper connectZk() {
        ZooKeeper zk = null;
        try {
            zk = new ZooKeeper(Constants.host, Constants.ZK_TIME_OUT, new Watcher() {
                @Override
                public void process(WatchedEvent event) {
                    // 判断是否连接zk集群
                    if (event.getState() == Event.KeeperState.SyncConnected) {
                        latch.countDown();//唤醒处于等待状态的连接
                    }
                }
            });
            latch.await(); //使当前线程处于等待状态
        } catch (Exception e) {
            e.printStackTrace();
        }
        return zk;
    }

注册 watcher

 /**
     * 观察/provider节点中的数据是否有变化
     *
     * @param zk
     */
    public void watchNode(ZooKeeper zk) {
        try {
            //观察/provider下面的结点是否有变化
            List<String> nodelist = zk.getChildren(Constants.ZK_REGISTER, new Watcher() {
                @Override
                public void process(WatchedEvent event) {
                    //子节点发生变化
                    if (event.getType() == Event.EventType.NodeChildrenChanged) {
                        watchNode(zk);
                    }
                }
            });
            //存放读取的地址数据
            List<String> datalist = new ArrayList<>();
            for (String node : nodelist) {
                byte[] data = zk.getData(Constants.ZK_REGISTER + "/" + node, false, null);
                datalist.add(new String(data));
            }
            //将datalist复制给urls
            urls = datalist;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

获取远程服务

/**
     * 获取rmi的远程服务对象
     */
    public <T> T lookupService(String url) {
        T remote = null;
        try {
            remote = (T) Naming.lookup(url);
        } catch (Exception e) {

            if (e instanceof ConnectException) {
                if (urls.size() != 0) {
                    url = urls.get(0);
                    return lookupService(url);
                }
            }
        }
        return remote;
    }

随机获取远程服务

**
     * 查找rmi服务，，通过随机算法，产生一个URL
     */
    public <T extends Remote> T lookup() {
        T service = null;
        int size = urls.size();
        if (size > 0) {
            String url = null;
            if (size == 1) {
                url = urls.get(0);
            } else {
                //产生随机数
                int random = ThreadLocalRandom.current().nextInt(size);
                url = urls.get(random);
            }
            System.out.println("==========" + url);
            service = lookupService(url);
        }
        return service;
    }

创建无参数构造方法、

 public ServiceConsumer(){
        ZooKeeper zk=connectZk();
        if (zk!=null){
            watchNode(zk);
        }
    }

创建启动类消费服务

package com.bjsxt.app;

import com.bjsxt.service.UserService;
import com.bjsxt.service.ServiceConsumer;

import java.rmi.RemoteException;

public class ZkClusterConsumerApp {
    public static void main(String[] args) throws RemoteException, InterruptedException {
        ServiceConsumer serviceConsumer=new ServiceConsumer();
        while (true){
            UserService userService=serviceConsumer.lookup();
            //调用远程的方法
            String result = userService.helloRem("zhangsan");
            System.out.println("result= "+result);
            Thread.sleep(3000);
        }
    }
}