//zookeeper，工具類
public class ZkUUtils {

    private static ZooKeeper zK;
    private static DefaultWatch defaultWatch = new DefaultWatch();
    private static CountDownLatch cc = new CountDownLatch(1);

    public static ZooKeeper getZk(){
        try {
            zK = new ZooKeeper("1277.0.0.1:2181/testConfig2",3000,defaultWatch);
            defaultWatch.setCountDownLatch(cc);
            cc.await();
        } 
 
catch (Exception e) {
            e.printStackTrace();
        }
        return zK;
    }
}

//預設監聽
@Data
public class DefaultWatch implements Watcher {

    CountDownLatch countDownLatch;

    @Override
    public void process(WatchedEvent event) {
        switch (event.getState()) {
            case
 
 Unknown:
                break;
            case Disconnected:
                break;
            case NoSyncConnected:
                break;
            case SyncConnected:
                countDownLatch.countDown();
                break;
            case AuthFailed:
                break;
            
 
case ConnectedReadOnly:
                break;
            case SaslAuthenticated:
                break;
            case Expired:
                break;
            case Closed:
                break;
        }
    }
}

//測試config

@Data
public class PConfig {
    private String config;
}

//基於zk回撥的配置熱更
@Data
public class PConfigWatchCallBack implements Watcher, AsyncCallback.StatCallback, AsyncCallback.DataCallback {

    private PConfig pConfig;

    private ZooKeeper zk;

    private CountDownLatch cc;

    @Override
    public void process(WatchedEvent event) {
        switch (event.getType()) {
            case None:
                break;
            case NodeCreated:
                zk.getData("/PTestConfig", this,this,"CCC");
                break;
            case NodeDeleted:
                pConfig.setConfig("");
                cc = new CountDownLatch(1);
                break;
            case NodeDataChanged:
                zk.getData("/PTestConfig", this,this,"CCC");
                break;
            case NodeChildrenChanged:
                break;
            case DataWatchRemoved:
                break;
            case ChildWatchRemoved:
                break;
            case PersistentWatchRemoved:
                break;
        }
    }



    //StatCallback
    @Override
    public void processResult(int rc, String path, Object ctx, Stat stat) {
        if(Objects.nonNull(stat)){
            zk.getData("/PTestConfig", this,this,"CCC");
        }
    }


    @Override
    public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
        String cfg = new String(data);
        pConfig.setConfig(cfg);
        cc.countDown();
    }

    public void await(){
        zk.exists("/PTestConfig",this,this,"AAA");
        try {
            cc.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

//測試類
public class PTestConfigMain {

    private ZooKeeper zk;

    @Before
    public void getZk(){
        zk = ZkUUtils.getZk();
    }

    @After
    public void close(){
        try {
            zk.close();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }


    @Test
    public void testConfig() throws InterruptedException {
        PConfigWatchCallBack pConfigWatchCallBack = new PConfigWatchCallBack();
        PConfig config = new PConfig();
        pConfigWatchCallBack.setPConfig(config);
        pConfigWatchCallBack.setZk(zk);
        CountDownLatch countDownLatch = new CountDownLatch(1);
        pConfigWatchCallBack.setCc(countDownLatch);

        pConfigWatchCallBack.await();

        while(true){
            if(config.getConfig().equals("")){
                System.out.println("配置被刪了");
                pConfigWatchCallBack.await();
            }else{
                System.out.println(config.getConfig());
            }
            TimeUnit.SECONDS.sleep(2);
        }

    }

}

在zookeeper中建立根節點，/testConfig2

在testConfig2下設定配置，PTestConfig，程式碼回去讀取節點PTestConfig的data，將資料讀到config類中，當節點被刪除後，測試類中配置提取會阻塞，節點建立或者修改時，會更新

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