直接上代码

中间存在一个bug,可能导致死锁.

import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.dao.DataAccessException;import org.springframework.data.redis.connection.RedisConnection;import org.springframework.data.redis.core.RedisCallback;import org.springframework.data.redis.core.RedisTemplate;import redis.clients.jedis.Jedis;import java.util.Objects;import java.util.UUID;import java.util.concurrent.ConcurrentHashMap;/** * Created by wenshiliang on 2017/6/5. * 不太可靠的基于redis的分布式锁 * setnx一个跟随jvm的uuid到redis,成功,认为占用锁成功,设置thread. * * 释放锁:判断是不是当前thread占用的,判断是不是当前jvm占用的,是,del redis key. * * * bug: 当异常退出jvm时,可能导致lock未释放.一般情况下设置了redis value的有效时长.如果在setnx后,expire前异常中断了jvm.可能会导致死锁. */public class RedisLock {    public static final int LOCK_DEATH_TIME = 300;//lock锁住时长,防止死锁,单位seconds    private static final Logger LOGGER = LoggerFactory.getLogger(RedisLock.class);    private final static String UID = UUID.randomUUID().toString();    private final static ConcurrentHashMap
    
      LOCK_MAP = new ConcurrentHashMap<>();    private RedisTemplate
     
       redisTemplate;    private Thread exclusiveOwnerThread;    private String key;    static {        //钩子,退出jvm时,移除lock        Runtime.getRuntime().addShutdownHook(new Thread(() -> {            System.out.println("redis lock shutdown hook");            LOCK_MAP.entrySet().forEach(entry -> {                entry.getKey().forceRelease();            });        }));    }    public RedisLock(RedisTemplate
      
        redisTemplate, String key) {        this.redisTemplate = redisTemplate;        this.key = key;    }    public void acquire() {        int i=1;        while (!acquire(1000)){            if(i++>300){                LOGGER.warn("lock acquire wait");            }        };    }    /**     * 获得锁     * @param time 毫秒     * @return     */    public boolean acquire(final long time) {        if (Objects.equals(Thread.currentThread(), exclusiveOwnerThread)) {            String result = redisTemplate.opsForValue().get(key);            if (UID.equals(result)) {                return true;            }            setExclusiveOwnerThread(null);        }        boolean flag = false;        long start = System.currentTimeMillis();        while (!flag && start <= System.currentTimeMillis() + time) {            flag = redisTemplate.execute(new RedisCallback
       
        () {                @Override                public Boolean doInRedis(RedisConnection connection) throws DataAccessException {                    Jedis jedis = (Jedis) connection.getNativeConnection();                    if (jedis.setnx(key, UID) == 1L) {                        jedis.expire(key, LOCK_DEATH_TIME);//300秒过期,防止死锁.如果在这步前jvm挂了,会导致一直死锁.                        LOCK_MAP.put(RedisLock.this,1);                        setExclusiveOwnerThread(Thread.currentThread());                        return true;                    }                    return false;                }            });        }        return flag;    }    public void release() {        if (Objects.equals(Thread.currentThread(), exclusiveOwnerThread)) {            String result = redisTemplate.opsForValue().get(key);            if (UID.equals(result)) {                LOCK_MAP.remove(this);                setExclusiveOwnerThread(null);                redisTemplate.delete(key);            }        }    }    protected void setExclusiveOwnerThread(Thread thread) {        exclusiveOwnerThread = thread;    }    private void forceRelease() {        String result = redisTemplate.opsForValue().get(key);        if (UID.equals(result)) {            LOCK_MAP.remove(this);            setExclusiveOwnerThread(null);            redisTemplate.delete(key);            LOGGER.info("force release lock: " + key);        }    }}