分布鎖實(shí)現(xiàn)方案和優(yōu)缺點(diǎn)先占坑
鎖重入待實(shí)現(xiàn)！！初斑！

//核心邏輯
tryLock()：搶鎖
       1 創(chuàng)建臨時(shí)序列節(jié)點(diǎn)，創(chuàng)建后阻塞，
       2 zk.create()成功后蔫耽，在回調(diào)函數(shù)中，通過(guò)zk.getChildren()獲取當(dāng)前根目錄下序列節(jié)點(diǎn)帕棉，
       3 在回調(diào)函數(shù)中判斷自己是否是第一節(jié)點(diǎn)针肥，是則獲得鎖，不是香伴，則watch前一個(gè)節(jié)點(diǎn)慰枕，
       4 如果前一個(gè)節(jié)點(diǎn)被刪除，則zk.getChildren()即纲，重復(fù)3具帮，4步驟；
work(): 搶鎖成功后的業(yè)務(wù)邏輯
unLock():釋放鎖

遺留問(wèn)題低斋，如何設(shè)計(jì)鎖重入蜂厅？

/**
 * @author haowq 2021/4/7 14:58
 */
public class WatchCallback implements Watcher, AsyncCallback.StringCallback, AsyncCallback.Children2Callback , AsyncCallback.StatCallback {
    private ZooKeeper zk;
    private String pathName;
    private String threadName;
    //Getter Setter
    private CountDownLatch latch = new CountDownLatch(1);

    public ZooKeeper getZk() {
        return zk;
    }

    public void setZk(ZooKeeper zk) {
        this.zk = zk;
    }


    public void tryLock(){
        //創(chuàng)建序列節(jié)點(diǎn)
        try {
            System.out.println(threadName + "create lock ....");
            zk.create("/lock",threadName.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL,this,"AsyncCallback.StringCallback");
            //阻塞，搶鎖膊畴，搶鎖操作在回調(diào)函數(shù)中完成
            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

    public void unLock(){
        try {
            zk.delete(pathName,-1);
            System.out.println(threadName + " over work....");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }

    }


    public void process(WatchedEvent event) {
        //如果第一個(gè)哥們掘猿，那個(gè)鎖釋放了，其實(shí)只有第二個(gè)收到了回調(diào)事件４娇纭稠通！
        //如果衬衬，不是第一個(gè)哥們，某一個(gè)改橘，掛了滋尉，也能造成他后邊的收到這個(gè)通知，從而讓他后邊那個(gè)跟去watch掛掉這個(gè)哥們前邊的飞主。狮惜。。
        switch (event.getType()) {
            case None:
            case NodeDataChanged:
            case NodeChildrenChanged:
            case NodeCreated:
                break;
            case NodeDeleted:
                zk.getChildren("/",false,this ,"syncCallback.Children2Callbac");
                break;
        }

    }

    // AsyncCallback.StringCallback
    @Override
    public void processResult(int rc, String path, Object ctx, String name) {
        System.out.println(name);
        pathName = name;
        //節(jié)點(diǎn)創(chuàng)建成功碌识，需要查看自己得序列號(hào) 判斷是否獲得鎖
        zk.getChildren(pathName,this,this,"Children2Callback");

    }


    //AsyncCallback.Children2Callbac
    @Override
    public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
        //查看自己的序列
        Collections.sort(children);

        String substring = path.substring(1);
        int i = children.indexOf(substring);
        //如果序列最小 獲得鎖
        if(i ==0){
            //yes
            System.out.println(threadName +" i am first....");
            try {
                zk.setData("/",threadName.getBytes(),-1);
                latch.countDown();
            } catch (KeeperException | InterruptedException e) {
                e.printStackTrace();
            }
        }else{
            //Watch 上一個(gè)序列點(diǎn)
            zk.exists("/"+children.get(i-1),this, this,"Children2Callback");
        }

    }

    //AsyncCallback.StatCallback
    @Override
    public void processResult(int rc, String path, Object ctx, Stat stat) {

    }
}