Redis分布式锁实现可重入性

Redis分布式锁实现可重入性思路： ThreadLock + 引用计数

什么是锁的可重入性？ 重入就是说某个线程已经获得某个锁，可以再次获取锁而不会出现死锁。

Java版本的可重入锁：

import java.util.HashMap;
import java.util.Map;

public class RedisWithReentrantLock {
    private ThreadLocal<Map> lockers = new ThreadLocal<>();
    private Jedis jedis;
    public RedisWithReentrantLock(Jedis jedis) {
        this.jedis = jedis;
    }
    private boolean _lock(String key) {
        return jedis.set(key, "", "nx", "ex", 5L) != null;
    }
    private void _unlock(String key) {
        jedis.del(key);
    }
    private Map <String, Integer> currentLockers() {
        Map <String, Integer> refs = lockers.get();
        if (refs != null) {
            return refs;
        }
        lockers.set(new HashMap<>());
        return lockers.get();
    }
    public boolean lock(String key) {
        Map refs = currentLockers();
        Integer refCnt = refs.get(key);
        if (refCnt != null) {
            refs.put(key, refCnt + 1);
            return true;
        }
        boolean ok = this._lock(key);
        if (!ok) {
            return false;
        }
        refs.put(key, 1);
        return true;
    }
    public boolean unlock(String key) {
        Map refs = currentLockers();
        Integer refCnt = refs.get(key);
        if (refCnt == null) {
            return false;
        }
        refCnt -= 1;
        if (refCnt > 0) {
            refs.put(key, refCnt);
        } else {
            refs.remove(key);
            this ._unlock(key);
        }
        return true;
    }
    public static void main(String[] args) {
        Jedis jedis = new Jedis();
        RedisWithReentrantLock redis = new RedisWithReentrantLock(jedis);
        System.out.println(redis.lock("codehole"));
        System.out.println(redis.lock("codehole"));
        System.out.println(redis.unlock("codehole"));
        System.out.println(redis.unlock("codehole"));
    }
}