Redis可重入锁java实现

可重入性是指线程在持有锁的情况下再次请求加锁，如果一个锁支持同一个线程的多次加锁，那么这个锁就是可重入的，redis分布式锁如果要支持可重入，需要对客户端的set方法进行包装，使用线程的ThreadLocal变量存储当前持有锁的计数

public class RedisWithReentrantLock{
  private ThreadLocal> 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 currentLockers(){
    Map 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;
  }
}