redis实现分布式锁。springboot下注入redisTemplate，redis的expire、delete等操作需要用redisTemplate而不能用opsForValue等。

RedisHelper.java

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;

@Component("redisHelper")
public class RedisHelper {


    @Autowired
    private RedisTemplate redisTemplate;

    public static final String LOCK_PREFIX = "redis_lock";

    /**
     * 分布式锁
     *
     * @param key key值
     * @param lock_expire 锁的过期时间，单位是毫秒
     * @return 是否获取到锁，true为获取到锁,false为未获取到。
     */
    public boolean lock(String key,int lock_expire) {
        String lock = LOCK_PREFIX + key;
        return (Boolean) redisTemplate.execute((RedisCallback) connection -> {

            long expireAt = System.currentTimeMillis() + lock_expire;
            Boolean acquire = connection.setNX(lock.getBytes(), String.valueOf(expireAt).getBytes());
            if (acquire) {
                return true;
            } else {
                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
                        byte[] oldValue = connection.getSet(lock.getBytes(), String.valueOf(System.currentTimeMillis() + lock_expire).getBytes());
                        // 防止死锁
                        return Long.parseLong(new String(oldValue)) < System.currentTimeMillis();
                    }
                }
            }
            return false;
        });
    }

    /**
     * 删除锁
     * @param key
     */
    public void delete(String key) {
        redisTemplate.delete(key);
    }
}