一分钟学会系列：Redis实现分布式锁

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/t1g2q3/article/details/87694643

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;
import java.util.Objects;

/**
 * Redis+Connection实现简单的分布式锁
 * 未能获取到锁应该按照业务逻辑进行阻塞或者放弃
 * @author Array
 */
@Component
public class DistributeLockByRedisTemplate {


    public static final String LOCK_PREFIX = "redis_lock";
    public static final int LOCK_EXPIRE = 300;

    @Autowired
    RedisTemplate redisTemplate;


    /**
     * 加锁
     * @param key key值
     * @return 是否获取到
     */
    public boolean lock(String key) {

        String lock = LOCK_PREFIX + key;

        return (Boolean) redisTemplate.execute((RedisCallback) connection -> {

            long expireAt = System.currentTimeMillis() + LOCK_EXPIRE + 1;

            /**
             * SET IF NOT EXISTS
             * 如果当前没有任何人持有锁，占有锁
             */
            Boolean acquire = connection.setNX(lock.getBytes(),
                    String.valueOf(expireAt).getBytes());

            if (acquire) {
                return true;
            } else {
                /**
                 * 如果当前存在锁，检查是否已经过期
                 */
                byte[] value = connection.get(lock.getBytes());

                if (Objects.nonNull(value) && value.length > 0) {

                    long expireTime = Long.parseLong(new String(value));

                    if (expireTime < System.currentTimeMillis()) {
                        /**
                         * 如果锁已经过期，获取锁
                         */
                        byte[] oldValue = connection.getSet(lock.getBytes(), String.valueOf(System.currentTimeMillis() + LOCK_EXPIRE + 1).getBytes());
                        return Long.parseLong(new String(oldValue)) < System.currentTimeMillis();
                    }
                }
            }
            return false;
        });
    }

    /**
     * 手动释放锁
     *
     * @param key
     */
    public void delete(String key) {
        redisTemplate.delete(key);
    }

}