package com.github.jedis.lock;

import redis.clients.jedis.Jedis;

/**
 * Redis distributed lock implementation.
 */
public class JedisLock {

    Jedis jedis;

    /**
     * Lock key path.
     */
    String lockKey;

    /**
     * Lock expiration in miliseconds.
     * 锁超时，防止线程在入锁以后，无限的执行等待
     */
    int expireMsecs = 60 * 1000;

    /**
     * Acquire timeout in miliseconds.
     * 锁等待，防止线程饥饿
     */
    int timeoutMsecs = 10 * 1000;

    boolean locked = false;

    /**
     * Detailed constructor with default acquire timeout 10000 msecs and lock expiration of 60000 msecs.
     *
     * @param jedis
     * @param lockKey lock key (ex. account:1, ...)
     */
    public JedisLock(Jedis jedis, String lockKey) {
        this.jedis = jedis;
        this.lockKey = lockKey;
    }

    /**
     * Detailed constructor with default lock expiration of 60000 msecs.
     *
     * @param jedis
     * @param lockKey      lock key (ex. account:1, ...)
     * @param timeoutMsecs acquire timeout in miliseconds (default: 10000 msecs)
     */
    public JedisLock(Jedis jedis, String lockKey, int timeoutMsecs) {
        this(jedis, lockKey);
        this.timeoutMsecs = timeoutMsecs;
    }

    /**
     * Detailed constructor.
     *
     * @param jedis
     * @param lockKey      lock key (ex. account:1, ...)
     * @param timeoutMsecs acquire timeout in miliseconds (default: 10000 msecs)
     * @param expireMsecs  lock expiration in miliseconds (default: 60000 msecs)
     */
    public JedisLock(Jedis jedis, String lockKey, int timeoutMsecs, int expireMsecs) {
        this(jedis, lockKey, timeoutMsecs);
        this.expireMsecs = expireMsecs;
    }

    /**
     * Detailed constructor with default acquire timeout 10000 msecs and lock expiration of 60000 msecs.
     *
     * @param lockKey lock key (ex. account:1, ...)
     */
    public JedisLock(String lockKey) {
        this(null, lockKey);
    }

    /**
     * Detailed constructor with default lock expiration of 60000 msecs.
     *
     * @param lockKey      lock key (ex. account:1, ...)
     * @param timeoutMsecs acquire timeout in miliseconds (default: 10000 msecs)
     */
    public JedisLock(String lockKey, int timeoutMsecs) {
        this(null, lockKey, timeoutMsecs);
    }

    /**
     * Detailed constructor.
     *
     * @param lockKey      lock key (ex. account:1, ...)
     * @param timeoutMsecs acquire timeout in miliseconds (default: 10000 msecs)
     * @param expireMsecs  lock expiration in miliseconds (default: 60000 msecs)
     */
    public JedisLock(String lockKey, int timeoutMsecs, int expireMsecs) {
        this(null, lockKey, timeoutMsecs, expireMsecs);
    }

    /**
     * @return lock key
     */
    public String getLockKey() {
        return lockKey;
    }

    /**
     * Acquire lock.
     *
     * @return true if lock is acquired, false acquire timeouted
     * @throws InterruptedException in case of thread interruption
     */
    public synchronized boolean acquire() throws InterruptedException {
        return acquire(jedis);
    }

    /**
     * Acquire lock.
     *
     * @param jedis
     * @return true if lock is acquired, false acquire timeouted
     * @throws InterruptedException in case of thread interruption
     */
    public synchronized boolean acquire(Jedis jedis) throws InterruptedException {
        //锁等待，防止线程饥饿
        int timeout = timeoutMsecs;
        while (timeout >= 0) {
            //锁超时，防止线程在入锁以后，无限的执行等待(为什么加1:因为可能有相同时间的操作,这样做不完美,但是实用)
            long expires = System.currentTimeMillis() + expireMsecs + 1;
            String expiresStr = String.valueOf(expires); //锁到期时间
            if (jedis.setnx(lockKey, expiresStr) == 1) {
                // lock acquired
                locked = true;
                return true;
            }

            String currentValueStr = jedis.get(lockKey); //redis里的时间
            if (currentValueStr != null && Long.parseLong(currentValueStr) < System.currentTimeMillis()) {
                //判断是否为空，不为空的情况下，如果被其他线程设置了值，则第二个条件判断是过不去的
                // lock is expired

                String oldValueStr = jedis.getSet(lockKey, expiresStr);
                //获取上一个锁到期时间，并设置现在的锁到期时间，
                //只有一个线程才能获取上一个线上的设置时间，因为jedis.getSet是同步的
                if (oldValueStr != null && oldValueStr.equals(currentValueStr)) {
                    //如过这个时候，多个线程恰好都到了这里，但是只有一个线程的设置值和当前值相同，他才有权利获取锁
                    // lock acquired
                    locked = true;
                    return true;
                }
            }
            timeout -= 100;
            Thread.sleep(100);
        }
        return false;
    }

    /**
     * Acqurired lock release.
     */
    public synchronized void release() {
        release(jedis);
    }

    /**
     * Acqurired lock release.
     */
    public synchronized void release(Jedis jedis) {
        if (locked) {
            jedis.del(lockKey);
            locked = false;
        }
    }
}

2.封装redis锁

•    实现参数的封装，一般都这么玩耍
•    实现修改为线程实现

<pre name="code" class="java">/**
 *  Copyright (c)  2011-2020 Panguso, Inc.
 *  All rights reserved.
 *
 *  This software is the confidential and proprietary information of Panguso, 
 *  Inc. ("Confidential Information"). You shall not
 *  disclose such Confidential Information and shall use it only in
 *  accordance with the terms of the license agreement you entered into with Panguso.
 */
package com.chinaso.phl.concurrent;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

import com.github.jedis.lock.JedisLock;

/**
 * 分布式锁的简单用法
 * @author  come from network
 * @date 2014-3-7
 */
public class SimpleLock {
    private static Logger    logger = LoggerFactory.getLogger(SimpleLock.class);

    private static JedisPool pool;
    private JedisLock        jedisLock;
    private String           lockKey;
    private Jedis            jedis;
    private int              timeoutMsecs;
    private int              expireMsecs;

    public SimpleLock(String lockKey) {
        this(lockKey, 3000, 300000);
    }

    public SimpleLock(String lockKey, int timeoutMsecs, int expireMsecs) {
        this.lockKey = lockKey;
        this.jedis = pool.getResource();
        this.timeoutMsecs = timeoutMsecs;
        this.expireMsecs = expireMsecs;
        this.jedisLock = new JedisLock(jedis, lockKey.intern(), timeoutMsecs, expireMsecs);
    }

    public void wrap(Runnable runnable) {
        long begin = System.currentTimeMillis();
        try {
            // timeout超时，等待入锁的时间，设置为3秒；expiration过期，锁存在的时间设置为5分钟
            logger.info("begin logck,lockKey={},timeoutMsecs={},expireMsecs={}", lockKey, timeoutMsecs, expireMsecs);
            if (jedisLock.acquire()) { // 启用锁
                runnable.run();
            } else {
               
                //logger.info("The time wait for lock more than [{}] ms ", timeoutMsecs);
            }
        } catch (Throwable t) {
            // 分布式锁异常
            logger.warn(t.getMessage(), t);
        } finally {
            this.lockRelease(jedisLock, jedis);
        }
        logger.info("[{}]cost={}", lockKey, System.currentTimeMillis() - begin);
    }

    /**
     * 释放锁,后期欲将离线计算的释放锁封装
     * 
     * @param lock
     * @param jedis
     * @author come from network
     * @date 2014-3-6
     */
    private void lockRelease(JedisLock lock,
                             Jedis jedis) {
        if (lock != null) {
            try {
                lock.release();// 则解锁
            } catch (Exception e) {
            }
        }
        if (jedis != null) {
            try {
                pool.returnResource(jedis);// 还到连接池里
            } catch (Exception e) {
            }
        }
        logger.info("release logck,lockKey={},timeoutMsecs={},expireMsecs={}", lockKey, timeoutMsecs, expireMsecs);
    }

    public static JedisPool getPool()
    {
        return pool;
    }

    public static synchronized void setPool(JedisPool pool)
    {
        SimpleLock.pool = pool;
    }

}

package com.chinaso.phl.concurrent;

import org.apache.commons.pool2.impl.GenericObjectPoolConfig;

import redis.clients.jedis.JedisPool;

/**
 * @author com from network
 * @date   2014-3-13
*/
public class SimpleLockTest {

    /**
     * @param args
     * @author com from network
     * @date   2014-3-13
    */
    public static void main(String[] args) {
        GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
        final JedisPool pool = new JedisPool(poolConfig, "192.168.142.237", 6379, 3000); //最后一个参数为密码
        SimpleLock.setPool(pool);//只需要初始化一次
        
        String key = "test";
        SimpleLock lock = new SimpleLock(key);
        lock.wrap(new Runnable() {
            @Override
            public void run() {
                //此处代码是锁上的
                System.out.println(111);
            }
        });
    }

}