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import cn.com.tpig.cache.redis.RedisService;
import cn.com.tpig.utils.SpringUtils;

//redis分散式鎖
public final class RedisLockUtil {

    private static final int defaultExpire = 60;

    private RedisLockUtil() {
        //
    }

    /**
     * 加鎖
     * @param key redis key
     * @param expire 過期時間，單位秒
     * @return true:加鎖成功，false，加鎖失敗
     */
    public static boolean lock(String key, int expire) {

        RedisService redisService = SpringUtils.getBean(RedisService.class);
        long status = redisService.setnx(key, "1");

        if(status == 1) {
            redisService.expire(key, expire);
            return true;
        }

        return false;
    }

    public static boolean lock(String key) {
        return lock2(key, defaultExpire);
    }

    /**
     * 加鎖
     * @param key redis key
     * @param expire 過期時間，單位秒
     * @return true:加鎖成功，false，加鎖失敗
     */
    public static boolean lock2(String key, int expire) {

        RedisService redisService = SpringUtils.getBean(RedisService.class);

        long value = System.currentTimeMillis() + expire;
        long status = redisService.setnx(key, String.valueOf(value));

        if(status == 1) {
            return true;
        }
        long oldExpireTime = Long.parseLong(redisService.get(key, "0"));
        if(oldExpireTime < System.currentTimeMillis()) {
            //超時
            long newExpireTime = System.currentTimeMillis() + expire;
            long currentExpireTime = Long.parseLong(redisService.getSet(key, String.valueOf(newExpireTime)));
            if(currentExpireTime == oldExpireTime) {
                return true;
            }
        }
        return false;
    }

    public static void unLock1(String key) {
        RedisService redisService = SpringUtils.getBean(RedisService.class);
        redisService.del(key);
    }

    public static void unLock2(String key) {    
        RedisService redisService = SpringUtils.getBean(RedisService.class);    
        long oldExpireTime = Long.parseLong(redisService.get(key, "0"));   
        if(oldExpireTime > System.currentTimeMillis()) {        
            redisService.del(key);    
        }
   }
}

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public void drawRedPacket(long userId) {
    String key = "draw.redpacket.userid:" + userId;

    boolean lock = RedisLockUtil.lock2(key, 60);
    if(lock) {
        try {
            //領取操作
        } finally {
            //釋放鎖
            RedisLockUtil.unLock(key);
        }
    } else {
        new RuntimeException("重複領取獎勵");
    }
}

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import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class DistributedLock implements Lock, Watcher{
    private ZooKeeper zk;
    private String root = "/locks";//根
    private String lockName;//競爭資源的標誌
    private String waitNode;//等待前一個鎖
    private String myZnode;//當前鎖
    private CountDownLatch latch;//計數器
    private int sessionTimeout = 30000;
    private List<Exception> exception = new ArrayList<Exception>();

    /**
     * 建立分散式鎖,使用前請確認config配置的zookeeper服務可用
     * @param config 127.0.0.1:2181
     * @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);
            Stat stat = zk.exists(root, false);
            if(stat == null){
                // 建立根節點
                zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
            }
        } catch (IOException e) {
            exception.add(e);
        } catch (KeeperException e) {
            exception.add(e);
        } catch (InterruptedException e) {
            exception.add(e);
        }
    }

    /**
     * zookeeper節點的監視器
     */
    public void process(WatchedEvent event) {
        if(this.latch != null) {
            this.latch.countDown();
        }
    }

    public void lock() {
        if(exception.size() > 0){
            throw new LockException(exception.get(0));
        }
        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) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
    }

    public boolean tryLock() {
        try {
            String splitStr = "_lock_";
            if(lockName.contains(splitStr))
                throw new LockException("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);
            System.out.println(myZnode + "==" + lockObjNodes.get(0));
            if(myZnode.equals(root+"/"+lockObjNodes.get(0))){
                //如果是最小的節點,則表示取得鎖
                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);
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(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;
    }

    private boolean waitForLock(String lower, long waitTime) throws InterruptedException, KeeperException {
        Stat stat = zk.exists(root + "/" + lower,true);
        //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);
            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();
        }
    }

    public void lockInterruptibly() throws InterruptedException {
        this.lock();
    }

    public Condition newCondition() {
        return null;
    }

    public class LockException extends RuntimeException {
        private static final long serialVersionUID = 1L;
        public LockException(String e){
            super(e);
        }
        public LockException(Exception e){
            super(e);
        }
    }
}