JAVA-各种场景获取锁

1、synchronized锁(并发竞争低，适用于单体服务。不考虑性能和效率,正常情况下完成降级)

--使用双重判断机制

synchronized (){

        }

2、ReentrantLock()锁(使用于单体服务，提高并发能力,通过阻塞来提高性能,支持多线程)

private final ReentrantLock lock=new ReentrantLock();


if(lock.tryLock()){
            try {

              

            } finally {
                //要主动释放锁
                lock.unlock();
            }
        }

3、redis 锁(可用做分布式)

 @Autowired
 private StringRedisTemplate redisTemplate;


   Boolean locak = redisTemplate.opsForValue().setIfAbsent("locak", uuid, 300, TimeUnit.SECONDS);

 if (locak) {
}//锁有时间可以不用手动释放


//redis自带脚本-判断纸盒和删除操作为原子操作删除锁

 String script = "if redis.call('get',KEYS[1]) == ARGV[1] then return redis.call('del',KEYS[1]) else return 0 end";
                //删除锁
                Long locak1 = redisTemplate.execute(new DefaultRedisScript(script, Long.class)
                        , Arrays.asList("locak"), uuid);

4、redissonClient锁(可用做分布式)

  @Resource
  RedissonClient redissonClient;

 RLock lock = redissonClient.getLock("catalogJson-lock");
        lock.lock();


 try {
            //业务逻辑
        } finally {
             lock.unlock();
        }

 4.1 redissonClient写锁(可用做分布式)

RReadWriteLock lock = redissonClient.getReadWriteLock("rw-lock");
        RLock rLock = lock.writeLock();


try {
            rLock.lock();
            //业务逻辑
            }else{

                
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            rLock.unlock();
        }

4.2 redissonClient读锁(可用做分布式)

RReadWriteLock lock = redissonClient.getReadWriteLock("rw-lock");
        RLock rLock = lock.readLock();


try {
            rLock.lock();
            //业务逻辑
            }else{

                
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            rLock.unlock();
        }