利用Zookeeper臨時(shí)節(jié)點(diǎn)(客戶端異常斷開連接后臨時(shí)節(jié)點(diǎn)自動(dòng)移除)或者Redis SETNX(set if not exists)(設(shè)置ttl)可以實(shí)現(xiàn)分布式鎖，這里先利用zk實(shí)現(xiàn)一個(gè)

1.啟動(dòng)zk

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2.代碼中watch節(jié)點(diǎn)

?　　2.1 Maven引入zk & zk client

　　2.2 代碼和注釋

import org.I0Itec.zkclient.ZkClient;

import java.util.concurrent.CountDownLatch;

public class ZKDistributeLockTest {

    public static void main(String[] args) {
        // 使用CountDownLunch控制線程同時(shí)執(zhí)行
        CountDownLatch countDownLatch = new CountDownLatch(1);
        // 開啟3個(gè)線程模擬分布式環(huán)境，分布式環(huán)境下每個(gè)進(jìn)程都是一個(gè)單獨(dú)的zkClient
        Thread t1 = new Thread(new TestThread(countDownLatch));
        Thread t2 = new Thread(new TestThread(countDownLatch));
        Thread t3 = new Thread(new TestThread(countDownLatch));
        t1.start();
        t2.start();
        t3.start();

        System.out.println("休眠1秒后執(zhí)行..."   System.currentTimeMillis());
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 倒計(jì)時(shí)結(jié)束
        countDownLatch.countDown();
    }


}

// 線程，嘗試在zk上創(chuàng)建臨時(shí)節(jié)點(diǎn)，創(chuàng)建成功則獲得鎖(執(zhí)行權(quán))
class TestThread implements Runnable {
    // 共享變量
    private static Integer CNT = 0;
    private ZkClient zkClient;
    private CountDownLatch countDownLatch;
    public TestThread(CountDownLatch countDownLatch) {
        this.countDownLatch = countDownLatch;
    }

    // 連接zk
    private void connect() {
        String threadName = Thread.currentThread().getName();
        try {
            System.out.println(threadName   " 等待執(zhí)行...");
            // 等待倒計(jì)時(shí)結(jié)束
            countDownLatch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(threadName   " 請(qǐng)求連接zk..."   System.currentTimeMillis());
        zkClient = new ZkClient("192.168.1.217:2181", 20000);
        System.out.println(threadName   " 連接成功...");
        // 輸出目錄信息測(cè)試
//        List<String> children = zkClient.getChildren("/");
//        children.forEach(System.out::println);
    }

    @Override
    public void run() {
        // 初始化連接(在各個(gè)線程里開啟連接，模擬分布式環(huán)境)
        connect();
        String threadName = Thread.currentThread().getName();

        // 競(jìng)爭(zhēng)鎖
        while (true) {
            try {
                System.out.println(threadName   " 開始競(jìng)爭(zhēng)鎖...");
                // 創(chuàng)建zk臨時(shí)節(jié)點(diǎn)
                zkClient.createEphemeral("/dl", "test");
                System.out.println(threadName   " 獲得鎖?。?！");
                // 獲得鎖后修改共享變量
                CNT   ;
                System.out.println(threadName   " 釋放了鎖..."   CNT);
                zkClient.delete("/dl");
                Thread.sleep(2000);
            } catch (Exception e) {
                // 創(chuàng)建臨時(shí)節(jié)點(diǎn)失敗，表示未獲得鎖
                System.out.println(threadName   " 未獲得鎖，將重試?。。?);
//                System.out.println(e.getMessage());
                try {
                    Thread.sleep(1500);
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }
}

3.測(cè)試結(jié)果

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