首選 安裝zookeeper，解壓  啟動， 看是否能正常啟動， 其中配置檔案中 需要copy zoo_sample 一份 命名成 zoo.cfg

然後啟動起來，  其次是修改你的ip和埠

然後小實現

private ZooKeeper zk;
private String root = "/locks";//根
private String lockName;
private String waitNode;//等待前一個鎖
private String myZnode;//當前鎖
private CountDownLatch latch;//計數器
private CountDownLatch connectedSignal
 
=new CountDownLatch(1);
private int sessionTimeout = 30000;
/**
 * 建立分散式鎖,使用前請確認config配置的zookeeper服務可用
 * @param config 192.168.1.90:2181
 * @param lockName 競爭資源標誌,lockName中不能包含單詞_lock_
 */
public DistributedLock(String config, String lockName){
    this.lockName = lockName;
// 建立一個與伺服器的連線
try {
        zk = new 
 
ZooKeeper(config, sessionTimeout, this);
connectedSignal.await();
Stat stat = zk.exists(root, false);//此去不執行 Watcher
if(stat == null){
            // 建立根節點
zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}
    } catch (IOException e) {
        System.out.println(e);
} catch 
 
(KeeperException e) {
        System.out.println(e);
} catch (InterruptedException e) {
        System.out.println(e);
}
}

設定監聽器

/**
 * zookeeper節點監聽器
 */
public void process(WatchedEvent event){
    //建立連線
if(event.getState() == Event.KeeperState.SyncConnected){
        connectedSignal.countDown();
        return ;
}
    if(this.latch !=null ){
        this.latch.countDown();
}


    return ;
}

預設呼叫鎖方法

public void lock() {
    try {
        if(this.tryLock()){
            System.out.println("Thread " + Thread.currentThread().getId() + " " +myZnode + " get lock true");
            return;
}
        else{
            waitForLock(waitNode, sessionTimeout);//等待鎖
}
    } catch (KeeperException e) {
        System.out.println(e);
} catch (InterruptedException e) {
        System.out.println(e);
}
}

public boolean tryLock() {
    try {
        String splitStr = "_lock_";
        if(lockName.contains(splitStr))
            System.out.println("lockName can not contains \\u000B");
//建立臨時子節點
myZnode = zk.create(root + "/" + lockName + splitStr, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
System.out.println(myZnode + " is created ");
//取出所有子節點
List<String> subNodes = zk.getChildren(root, false);
//取出所有lockName的鎖
List<String> lockObjNodes = new ArrayList<String>();
        for (String node : subNodes) {
            String _node = node.split(splitStr)[0];
            if(_node.equals(lockName)){
                lockObjNodes.add(node);
}
        }
        Collections.sort(lockObjNodes);
        if(myZnode.equals(root+"/"+lockObjNodes.get(0))){
            //如果是最小的節點,則表示取得鎖
System.out.println(myZnode + "==" + lockObjNodes.get(0));
            return true;
}
        //如果不是最小的節點，找到比自己小1的節點
String subMyZnode = myZnode.substring(myZnode.lastIndexOf("/") + 1);
waitNode = lockObjNodes.get(Collections.binarySearch(lockObjNodes, subMyZnode) - 1);//找到前一個子節點
} catch (KeeperException e) {
        System.out.println(e);
} catch (InterruptedException e) {
        System.out.println(e);
}
    return false;
}
public boolean tryLock(long time, TimeUnit unit) {
    try {
        if(this.tryLock()){
            return true;
}
        return waitForLock(waitNode,time);
} catch (Exception e) {
        e.printStackTrace();
}
    return false;
}

判斷節點數  是否是最小的

private boolean waitForLock(String lower, long waitTime) throws InterruptedException, KeeperException {
    Stat stat = zk.exists(root + "/" + lower,true);//同時註冊監聽。
    //判斷比自己小一個數的節點是否存在,如果不存在則無需等待鎖,同時註冊監聽
if(stat != null){
        System.out.println("Thread " + Thread.currentThread().getId() + " waiting for " + root + "/" + lower);
        this.latch = new CountDownLatch(1);
        this.latch.await(waitTime, TimeUnit.MILLISECONDS);//等待，這裡應該一直等待其他執行緒釋放鎖
this.latch = null;
}
    return true;
}
public void unlock() {
    try {
        System.out.println("unlock " + myZnode);
zk.delete(myZnode,-1);
myZnode = null;
zk.close();
} catch (InterruptedException e) {
        e.printStackTrace();
} catch (KeeperException e) {
        e.printStackTrace();
}
}

最後測試

public static void main(String[] args){
    DistributedLock lock   = new DistributedLock("192.168.1.90:2181","lock");
lock.lock();
//共享資源
if(lock != null)
        lock.unlock();
}