redis RedisTemplate实现分布式锁

独角兽企业重金招聘Python工程师标准>>>

话不多说，上代码：

import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.redis.core.RedisCallback;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.core.ValueOperations;import org.ponent; import java.util.Objects;import java.util.concurrent.TimeUnit; /** * Description: 通用Redis帮助类 * User: zhouzhou * Date: -09-05 * Time: 15:39 */@Componentpublic class CommonRedisHelper { public static final String LOCK_PREFIX = "redis_lock"; public static final int LOCK_EXPIRE = 300; // ms@Autowired RedisTemplate redisTemplate; /*** 最终加强分布式锁** @param key key值* @return 是否获取到*/ public boolean lock(String key){ String lock = LOCK_PREFIX + key; // 利用lambda表达式 return (Boolean) redisTemplate.execute((RedisCallback) connection -> { long expireAt = System.currentTimeMillis() + LOCK_EXPIRE + 1; 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 + 1).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);} }

如何使用呢,导入工具类后:

明星出轨Service{public List get明星出轨(String id){List list = getRedis(id);if(list == null){boolean flag = CommonRedisHelper.lock(id);if(flag){list = findListBydB(id);redis.set(id).value(list);CommonRedisHelper.delete(id);}else{Threed.sleep(5000);return this.get明星出轨(id);}}return list;}}

加锁成功执行完逻辑后, 必须解锁, 否则只能靠锁机制来解锁了不建议这么做。在web开发时，我们使用redis更多是使用redisTemplate，所以了解redisTemplate实现分布式锁势在必行。

PS：现在添加另一个更保持原子性的redis分布式锁的工具类

public class RedisTool {@AutowiredRedisTemplate redisTemplate;private static final Long SUCCESS = 1L;/*** 获取锁* @param lockKey* @param value* @param expireTime：单位-秒* @return*/public boolean getLock(String lockKey, String value, int expireTime){boolean ret = false;try{String script = "if redis.call('setNx',KEYS[1],ARGV[1]) then if redis.call('get',KEYS[1])==ARGV[1] then return redis.call('expire',KEYS[1],ARGV[2]) else return 0 end end";RedisScript<String> redisScript = new DefaultRedisScript<>(script, String.class);Object result = redisTemplate.execute(redisScript, Collections.singletonList(lockKey),value,expireTime);if(SUCCESS.equals(result)){return true;}}catch(Exception e){}return ret;}/*** 释放锁* @param lockKey* @param value* @return*/public boolean releaseLock(String lockKey, String value){String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";RedisScript<String> redisScript = new DefaultRedisScript<>(script, String.class);Object result = redisTemplate.execute(redisScript, Collections.singletonList(lockKey),value);if(SUCCESS.equals(result)) {return true;}return false;}}

在使用上有一些小不同，可以根据业务进行融合

明星出轨Service{public List get明星出轨(String id){List list = getRedis(id);if(list == null){boolean flag = redisTool.getLock("lockKey_"+id,id,1000 * 60);if(flag){list = findListBydB(id);redis.set(id).value(list);redisTool.releaseLock("lockKey_"+id,id);}else{Threed.sleep(5000);return this.get明星出轨(id);}}return list;}}

PS：我们有发现一种新的分布式锁，这个方法也可以实现分布式锁

boolean flag = redisTemplate.opsForValue().setIfAbsent(key,value);