Jedis分散式鎖實現

package com.wdzj.redis.distributed.lock;

import java.util.UUID;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.exceptions.JedisException;

/**
 * Jedis分散式鎖實現
 * 
 * @author wuwenyu
 *
 */
public class JedisLock {

    private static final Lock NO_LOCK = new Lock(new UUID(0l, 0l), 0l);

    private static final int ONE_SECOND = 1000;

    // 鎖過期時間
    public static final int DEFAULT_EXPIRY_TIME_MILLIS = 60 * ONE_SECOND;
    private final int lockExpiryInMillis;

    // 等待獲取鎖時間
    public static final int DEFAULT_ACQUIRE_TIMEOUT_MILLIS = 10 * ONE_SECOND;
    private final int acquiryTimeoutInMillis;

    // 過獲取過程中的間隔時間
    public static final int DEFAULT_ACQUIRY_RESOLUTION_MILLIS = 100;

    // jedis連接池
    private final JedisPool pool;

    // 加鎖路徑
    private final String lockKeyPath;

    // 抓取鎖UUID 鎖標識
    private final UUID lockUUID;

    private Lock lock = null;

    public JedisLock(JedisPool pool, String lockKey) {
        this(pool, lockKey, DEFAULT_ACQUIRE_TIMEOUT_MILLIS,
                DEFAULT_EXPIRY_TIME_MILLIS);
    }

    public JedisLock(JedisPool pool, String lockKey, int acquireTimeoutMillis) {
        this(pool, lockKey, acquireTimeoutMillis, DEFAULT_EXPIRY_TIME_MILLIS);
    }

    public JedisLock(JedisPool pool, String lockKey, int acquireTimeoutMillis,
            int expiryTimeMillis) {
        this.pool = pool;
        this.lockKeyPath = lockKey;
        this.acquiryTimeoutInMillis = acquireTimeoutMillis;
        this.lockExpiryInMillis = expiryTimeMillis + 1;
        this.lockUUID = UUID.randomUUID();
    }

    /**
     * 獲取redis分散式鎖
     * @return
     * @throws Exception
     */
    public synchronized boolean acquire() throws Exception {
        Jedis jedis = null;
        try {
            jedis = pool.getResource();
            int timeout = acquiryTimeoutInMillis;
            while (timeout >= 0) {
                final Lock newLock = new Lock(lockUUID,
                        System.currentTimeMillis() + lockExpiryInMillis);
                if (jedis.setnx(lockKeyPath, newLock.toString()) == 1) {
                    this.lock = newLock;
                    return true;
                }

                final String currentValueStr = jedis.get(lockKeyPath);
                final Lock currentLock = Lock.fromString(currentValueStr);
                if (currentLock.isExpiredOrMine(lockUUID)) {
                    String oldValueStr = jedis.getSet(lockKeyPath,
                            newLock.toString());
                    if (oldValueStr != null
                            && oldValueStr.equals(currentValueStr)) {
                        this.lock = newLock;
                        return true;
                    }
                }

                timeout -= DEFAULT_ACQUIRY_RESOLUTION_MILLIS;
                Thread.sleep(DEFAULT_ACQUIRY_RESOLUTION_MILLIS);
            }
        } catch (JedisException e) {
            if (jedis != null) {
                pool.returnBrokenResource(jedis);
            }
        } finally {
            if (jedis != null) {
                pool.returnResource(jedis);
            }
        }

        return false;
    }

    /**
     * 釋放redis分散式鎖
     * @throws Exception
     */
    public synchronized void release() throws Exception{
        if (this.lock != null) {
            Jedis jedis = null;
            try {
                jedis = pool.getResource();
                jedis.del(lockKeyPath);
            } catch (JedisException e) {
                if (jedis != null) {
                    pool.returnBrokenResource(jedis);
                }
            } finally {
                if (jedis != null) {
                    pool.returnResource(jedis);
                }
                this.lock = null;
            }
            
        }
    }

    protected static class Lock {
        private UUID uuid;
        private long expiryTime;

        protected Lock(UUID uuid, long expiryTimeInMillis) {
            this.uuid = uuid;
            this.expiryTime = expiryTimeInMillis;
        }

        protected static Lock fromString(String text) {
            try {
                String[] parts = text.split(":");
                UUID theUUID = UUID.fromString(parts[0]);
                long theTime = Long.parseLong(parts[1]);
                return new Lock(theUUID, theTime);
            } catch (Exception any) {
                return NO_LOCK;
            }
        }

        public UUID getUUID() {
            return uuid;
        }

        public long getExpiryTime() {
            return expiryTime;
        }

        @Override
        public String toString() {
            return uuid.toString() + ":" + expiryTime;
        }

        boolean isExpired() {
            return getExpiryTime() < System.currentTimeMillis();
        }

        boolean isExpiredOrMine(UUID otherUUID) {
            return this.isExpired() || this.getUUID().equals(otherUUID);
        }
    }

}