zookeeper分布式锁实例_zk的分布式所代码实例

<dependency>
	<groupId>com.101tec</groupId>
	<artifactId>zkclient</artifactId>
	<version>0.10</version>
</dependency>

如果有一把锁，被多个人给竞争，此时多个人会排队，第一个拿到锁的人会执行，然后释放锁；后面的每个人都会去监听**排在自己前面**的那个人创建的 node 上，一旦某个人释放了锁，排在自己后面的人就会被 zookeeper 给通知，一旦被通知了之后，就 ok 了，自己就获取到了锁，就可以执行代码了。
```java
public class ZooKeeperDistributedLock {
 
    //private ZooKeeper zk;
    private ZkClient zk;
    private String locksRoot = "/locks";
    private String productId;
    private String waitNode;
    private String lockNode;
    private CountDownLatch latch;
    private int sessionTimeout = 30000;
 
    public ZooKeeperDistributedLock() {
 
        try {
                                         
            String address="192.168.31.187:2181,192.168.31.19:2181,192.168.31.227:2181";
            zk = new ZkClient(address, sessionTimeout, sessionTimeout);
        } catch (IOException e) {
            throw new LockException(e);
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
    }
 
 
    public void acquireDistributedLock() {
        try {
            if (this.tryLock()) {
                return;
            } else {
                waitForLock(waitNode, sessionTimeout);
                acquireDistributedLock();
            }
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
    }
 
    public boolean tryLock() {
        try {
 		   
            lockNode = this.client.createEphemeralSequential(locksRoot+ "/", "1");
   
            // 看看刚创建的节点是不是最小的节点
	    // locks：10000000000，10000000001，10000000002
            List<String> locks = zk.getChildren(locksRoot);
            Collections.sort(locks);
	
            if(lockNode.equals(locksRoot+"/"+ locks.get(0))){
                System.out.println(Thread.currentThread().getName() + ":获取锁成功");
                //如果是最小的节点,则表示取得锁
                return true;
            }
	
            //如果不是最小的节点，找到比自己小1的节点
	  int previousLockIndex = -1;
            for(int i = 0; i < locks.size(); i++) {
		if(lockNode.equals(locksRoot + “/” + locks.get(i))) {
	         	    previousLockIndex = i - 1;
		    break;
		}
	   }
	   
	   this.waitNode = locks.get(previousLockIndex);
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
        return false;
    }
 
    private boolean waitForLock(String waitNode, long waitTime) throws 
        InterruptedException, KeeperException {
        Stat stat = zk.exists(locksRoot + "/" + waitNode, true);
        this.latch = new CountDownLatch(1);
        
        IZkDataListener listener = new IZkDataListener() {
 	    @Override			
            public void handleDataChange(String arg0, Object arg1) throws Exception { 			
            } 			
            @Override			
            public void handleDataDeleted(String arg0) 
                throws Exception {	            
                    System.out.println("节点被删除了，开始抢锁");
	            cdl.countDown();
            } 		
        };	
	
        // 完成watcher注册		
        this.client.subscribeDataChanges(beforePath, listener);
 
        if (stat != null) {
            this.latch.await(waitTime, TimeUnit.MILLISECONDS);
            this.latch = null;
        }
 
        // 取消注册
	this.client.unsubscribeDataChanges(beforePath, listener);
        return true;
    }
 
    public void unlock() {
        try {
            // 删除/locks/10000000000节点
            // 删除/locks/10000000001节点
            System.out.println("unlock " + lockNode);
            zk.delete(lockNode);
            System.out.println(Thread.currentThread().getName() 
                + "所有锁释放成功:删除zk节点");
            lockNode = null;
            zk.close();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }
    }
 
    public class LockException extends RuntimeException {
        private static final long serialVersionUID = 1L;
 
        public LockException(String e) {
            super(e);
        }
 
        public LockException(Exception e) {
            super(e);
        }
    }
}

public class OrderCodeGenerator {
 
    private int i = 0;
 
    public String getOrderCode() {
 
	Date now = new Date();
 
	SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss-");
 
	return sdf.format(now) + ++i;
 
    }
}

 
public class OrderServiceImplWithZkDis implements OrderService {
 
 
	private static OrderCodeGenerator org = new OrderCodeGenerator();
 
 
	private Lock lock = new ZooKeeperDistributedLock();
 
 
	@Override
 
	public void createOrder() {
 
		String orderCode = null;
 
 		try {
 
			lock.acquireDistributedLock();
 
 			orderCode = org.getOrderCode();
 
			//TestReLock();
 
			System.out.println(Thread.currentThread().getName() + "生成订单：" + orderCode);
 
		} catch (Exception e) {
 
			e.printStackTrace();
 
		} finally {
 
			lock.unlock();
 
		}
 
	}
 
 
        /**
	public void TestReLock() {
 
		lock.acquireDistributedLock();
 
		System.out.println(Thread.currentThread().getName() + "测试重入锁成功...");
 
		lock.unlock();
 
	}
        **/ 
 
 
	public static void main(String[] args) {
 
		int num = 5;
 
		CyclicBarrier cyclicBarrier = new CyclicBarrier(num);
 
		for (int i = 0; i < num; i++) {
 
			new Thread(new Runnable() {
 
				@Override
 
				public void run() {
 
					OrderService orderService = new OrderServiceImplWithZkDis();
 
					System.out.println(Thread.currentThread().getName() + "： 我准备好了");
 
					try {
						cyclicBarrier.await();
 
					} catch (Exception e) {
 
						e.printStackTrace();
 
					}
 
 					orderService.createOrder();
 
				}
 
			}).start();
 
		}
 
	}
 
 }

Thread-2：我准备好了
Thread-3：我准备好了
Thread-1：我准备好了
Thread-5：我准备好了
Thread-4：我准备好了
Thread-4：获取锁成功
Thread-4生成订单：2018-07-12-13-12-09-1
Thread-4所有锁释放成功：删除ZK节点
节点删除了，开始抢锁
Thread-5：获取锁成功
Thread-5生成订单：2018-07-12-13-12-11-2
Thread-5所有锁释放成功：删除ZK节点
节点删除了，开始抢锁
Thread-2：获取锁成功
Thread-2生成订单：2018-07-12-13-12-14-3
Thread-2所有锁释放成功：删除ZK节点
节点删除了，开始抢锁
Thread-3：获取锁成功
Thread-3生成订单：2018-07-12-13-12-17-4
Thread-3所有锁释放成功：删除ZK节点
节点删除了，开始抢锁
Thread-1：获取锁成功
Thread-1生成订单：2018-07-12-13-12-21-5
Thread-1所有锁释放成功：删除ZK节点
节点删除了，开始抢锁