package com.central.common.redis.lock;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.data.redis.connection.RedisStringCommands;
import org.springframework.data.redis.connection.ReturnType;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.types.Expiration;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
/**
* redis分布式锁实现
*
* @author zlt
* @date 2018/5/29 14:16
*
* Blog: https://zlt2000.gitee.io
* Github: https://github.com/zlt2000
*
* @deprecated 建议使用Redisson的实现方式 {@link RedissonDistributedLock}
*/
@Slf4j
@ConditionalOnClass(RedisTemplate.class)
@Deprecated
public class RedisDistributedLock {
@Autowired
private RedisTemplate redisTemplate;
private ThreadLocal lockFlag = new ThreadLocal<>();
private static final String UNLOCK_LUA;
/*
* 通过lua脚本释放锁,来达到释放锁的原子操作
*/
static {
UNLOCK_LUA = "if redis.call(\"get\",KEYS[1]) == ARGV[1] " +
"then " +
" return redis.call(\"del\",KEYS[1]) " +
"else " +
" return 0 " +
"end ";
}
public RedisDistributedLock(RedisTemplate redisTemplate) {
super();
this.redisTemplate = redisTemplate;
}
/**
* 获取锁
*
* @param key 锁的key
* @param expire 获取锁超时时间
* @param retryTimes 重试次数
* @param sleepMillis 获取锁失败的重试间隔
* @return 成功/失败
*/
public boolean lock(String key, long expire, int retryTimes, long sleepMillis) {
boolean result = setRedis(key, expire);
// 如果获取锁失败,按照传入的重试次数进行重试
while ((!result) && retryTimes-- > 0) {
try {
log.debug("get redisDistributeLock failed, retrying..." + retryTimes);
Thread.sleep(sleepMillis);
} catch (InterruptedException e) {
log.warn("Interrupted!", e);
Thread.currentThread().interrupt();
}
result = setRedis(key, expire);
}
return result;
}
private boolean setRedis(final String key, final long expire) {
try {
boolean status = redisTemplate.execute((RedisCallback) connection -> {
String uuid = UUID.randomUUID().toString();
lockFlag.set(uuid);
byte[] keyByte = redisTemplate.getStringSerializer().serialize(key);
byte[] uuidByte = redisTemplate.getStringSerializer().serialize(uuid);
boolean result = connection.set(keyByte, uuidByte, Expiration.from(expire, TimeUnit.MILLISECONDS), RedisStringCommands.SetOption.ifAbsent());
return result;
});
return status;
} catch (Exception e) {
log.error("set redisDistributeLock occured an exception", e);
}
return false;
}
/**
* 释放锁
* @param key 锁的key
* @return 成功/失败
*/
public boolean releaseLock(String key) {
// 释放锁的时候,有可能因为持锁之后方法执行时间大于锁的有效期,此时有可能已经被另外一个线程持有锁,所以不能直接删除
try {
// 使用lua脚本删除redis中匹配value的key,可以避免由于方法执行时间过长而redis锁自动过期失效的时候误删其他线程的锁
// spring自带的执行脚本方法中,集群模式直接抛出不支持执行脚本的异常,所以只能拿到原redis的connection来执行脚本
Boolean result = redisTemplate.execute((RedisCallback) connection -> {
byte[] scriptByte = redisTemplate.getStringSerializer().serialize(UNLOCK_LUA);
return connection.eval(scriptByte, ReturnType.BOOLEAN, 1
, redisTemplate.getStringSerializer().serialize(key)
, redisTemplate.getStringSerializer().serialize(lockFlag.get()));
});
return result;
} catch (Exception e) {
log.error("release redisDistributeLock occured an exception", e);
} finally {
lockFlag.remove();
}
return false;
}
}