自定义分布式锁注解

定义redis分布式锁方法

https://www.cnblogs.com/wangyingshuo/p/14510524.html

public interface DistributedLock extends Lock {

    /**
     * 尝试获取分布式锁
     *
     * @param lockKey       锁
     * @param requestId     请求标识
     * @param expireSeconds 锁有效时间
     * @param overTime      超时时间
     * @param timeUnit      时间单位
     * @return 是否获取成功
     * @throws InterruptedException 中断异常
     */
    boolean tryLock(String lockKey, String requestId, int expireSeconds, int overTime, TimeUnit timeUnit) throws InterruptedException;


    /**
     * 尝试获取分布式分段锁
     * @param lockKey
     * @param segments 分段标识
     * @param requestId
     * @param expireSeconds
     * @param overTime
     * @param timeUnit
     * @return 返回成功加锁的段
     * @throws InterruptedException
     */
    String tryLock(String lockKey, List<String> segments , String requestId, int expireSeconds, int overTime, TimeUnit timeUnit) throws InterruptedException ;


        /**
         * 释放分布式锁
         *
         * @param lockKey   锁
         * @param requestId 请求标识
         */
    boolean unlock(String lockKey, String requestId);
}

实现加锁的方法

加锁本质是为了实现互斥，只让一个访问资源。redis分布式锁是根据lockKey这个key去查是否有对应的value,如果值不存在，说明并没有人访问资源，则加锁成功。如果值存在，说明已经有人在访问资源，则加锁失败。

@Component
public class RedisDistributedLock implements DistributedLock {

    /**
     * 成功
     */
    private final static Long SUCCESS = 1L;
    /**等待200ms*/
    private final static Long WAIT_TIME = 200L;


    /**分段锁间的时间间隔*/
    private final static Long SEGMENT_WAIT_TIME = 5L;


    private final static Long WAIT_TIME_1 = 50L;


    /**
     * 缓存
     */
    @Autowired
    private RedisTemplate<String, Object> redisTemplate;

    @Override
    public void lock() {
        throw new UnsupportedOperationException();
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        throw new InterruptedException();
    }

    @Override
    public boolean tryLock() {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean tryLock(String lockKey, String requestId, int expireSeconds, int overTime, TimeUnit timeUnit) throws InterruptedException {
        long lastTime = System.nanoTime();
        // 获取锁的超时时间
        long timeout = timeUnit.toNanos(overTime);
        for (; ; ) {
            boolean isGet = tryGetDistributedLock(lockKey, requestId, expireSeconds, timeUnit);

            // 获取成功
            if (isGet) {
                return true;
            }
            long now = System.nanoTime();

            // 超时
            if (timeout <= 0) {
                throw new DefinitelyRuntimeException("当前活动火热,稍后再试...");
            }
            //等待WAIT_TIME
            Thread.sleep(WAIT_TIME);

            timeout -= now - lastTime;
            lastTime = now;

            // 线程已被销毁
            if (Thread.interrupted()) {
                throw new InterruptedException();
            }
        }
    }


    public String tryLock(String lockKey, List<String> segments , String requestId, int expireSeconds, int overTime, TimeUnit timeUnit) throws InterruptedException {

        long lastTime = System.nanoTime();
        // 获取锁的超时时间
        long timeout = timeUnit.toNanos(overTime);
        for (; ; ) {
            for (int i = 0; i < segments.size(); i++) {
                boolean sucess = tryGetDistributedLock(lockKey + segments.get(i), requestId, expireSeconds, timeUnit);
                if (sucess) {
                    return  segments.get(i);
                }
                long now = System.nanoTime();
                // 超时
                if (timeout <= 0) {
                    throw new DefinitelyRuntimeException("加锁超时");
                }
                //等待WAIT_TIME
                Thread.sleep(SEGMENT_WAIT_TIME);

                timeout -= now - lastTime;
                lastTime = now;

                // 线程已被销毁
                if (Thread.interrupted()) {
                    throw new InterruptedException();
                }
            }
            //等待WAIT_TIME
            Thread.sleep(WAIT_TIME_1);
        }
    }




    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean unlock(String lockKey, String requestId) {
        return releaseDistributedLock(lockKey, requestId);
    }

    @Override
    public void unlock() {
        throw new UnsupportedOperationException();
    }

    @SuppressWarnings("NullableProblems")
    @Override
    public Condition newCondition() {
        throw new UnsupportedOperationException();
    }

    /**
     * 尝试获取分布式锁
     *
     * @param lockKey       锁
     * @param requestId     请求标识
     * @param expireSeconds 缓存有效时间
     * @param timeUnit      时间单位
     * @return 是否获取成功
     */
    private boolean tryGetDistributedLock(String lockKey, String requestId, int expireSeconds, TimeUnit timeUnit) {
        // 设置锁，不存在时才能设置成功，表示被锁住
        if (redisTemplate == null) {
            return false;
        }
        Boolean isLock = redisTemplate.opsForValue().setIfAbsent(lockKey, requestId, expireSeconds, timeUnit);

        if (isLock != null && isLock) {
            return true;
        }
        return false;
    }

    /**
     * 释放分布式锁
     *
     * @param lockKey   锁
     * @param requestId 请求标识
     * @return 是否释放成功
     */
    private boolean releaseDistributedLock(String lockKey, String requestId) {
        // 用脚本来保证同步操作
        String script =
                "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
        RedisScript<Long> redisScript = new DefaultRedisScript<>(script, Long.class);
        Long result = redisTemplate.execute(redisScript, Collections.singletonList(lockKey), requestId);
        return SUCCESS.equals(result);
    }
}

自定义一个加锁注解

/**
 * 分布式锁注解
 *
 */
@Documented
@Inherited
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Dl {

    /**
     * 锁定的缓存key名称，若为空，则为类完整名 + 方法名 + 后缀
     *
     * @return 锁定的缓存key名称
     */
    String value() default "";

    /**
     * 缓存key后缀参数所在位置，与{@link #spEl()}属性冲突，优先级低于{@link #spEl()}
     *
     * @return 位置
     */
    int suffixKeyIndex() default -1;

    /**
     * 同步锁定的时间，单位秒，默认60
     *
     * @return 同步锁定的时间
     */
    int lockTimeSeconds() default 60;

    /**
     * 获取锁的超时时间
     *
     * @return 获取锁的超时时间
     */
    int overTime() default 60;

    /**
     * 时间单位
     *
     * @return 时间单位
     */
    TimeUnit timeUnit() default TimeUnit.SECONDS;

    /**
     * 缓存key后缀的spEl表达式，与{@link #suffixKeyIndex()}属性冲突，优先级高于{@link #suffixKeyIndex()}
     *
     * @return 缓存key后缀的spEl表达式
     */
    String spEl() default "";
}

增加切面，指向自定义的锁注解

当每次使用Dl注解的时候，都会调用下面的distributedLock()方法，即添加了注解的方法都会加分布式锁。

@Aspect
@Component
@Order(-1)
@ConditionalOnBean(DistributedLock.class)
public class DistributedAspect {

    /**
     * 分布式锁
     */
    @Autowired
    private DistributedLock distributedLock;

    /**
     * @param proceedingJoinPoint proceedingJoinPoint
     */
    @Around("@annotation(com.nascent.ecrp.mall.springframework.distribute.Dl)")
    public Object distributedLock(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
        String requestId = UUID.randomUUID().toString();
        MethodSignature methodSignature = (MethodSignature) proceedingJoinPoint.getSignature();
        Method method = methodSignature.getMethod();
        Dl distributedKey = method.getAnnotation(Dl.class);
        String lockKey = distributedKey.value();

        if (StringUtils.isBlank(lockKey)) {
            // 若默认的key为空，则生成一个
            lockKey = method.getDeclaringClass().getName() + ":" + method.getName();
        }
        // 解析缓存key的后缀
        int suffixKeyIndex = distributedKey.suffixKeyIndex();
        String suffixKey = "";
        String spEl = distributedKey.spEl();

        if (StringUtils.isNotBlank(spEl)) {
            suffixKey = ":" + SpElUtils
                .getValue(spEl, proceedingJoinPoint.getArgs(), methodSignature.getParameterNames());

        } else if (suffixKeyIndex > -1) {
            Object[] args = proceedingJoinPoint.getArgs();
            suffixKey += ":" + args[suffixKeyIndex];
        }
        lockKey += suffixKey;
        lockKey = "distributed_lock:" + lockKey;
        try {
            if (distributedLock.tryLock(lockKey, requestId, distributedKey.lockTimeSeconds(), distributedKey.overTime(), distributedKey.timeUnit())) {
                return proceedingJoinPoint.proceed();

            } else {
                throw new DefinitelyRuntimeException("系统挤爆了，请稍后再试");
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new DefinitelyRuntimeException(e);

        } finally {
            distributedLock.unlock(lockKey, requestId);
        }
    }
}

方法中如何使用自定义的注解

 @Override
    @Dl(value = "submit", spEl = "#customer.openId")
    @Transactional
    public BeanCommonResult cancelLike(FreeTrialReportLikeMobileRequest request, Customer customer) {

        WmActivityFreeTrialLogDO freeTrialLog = WmActivityFreeTrialLogDao.dao().findLogByParticipateId(request.getTrialLogGuid());
        if (freeTrialLog == null) {
            throw new BaseRuntimeException("参数有误");
        }

        WmActivityFreeTrialReportLikeLog log = trialReportLikeLogMapper.selectByUserActLog(request.getTrialLogGuid(), customer.getOpenId());

        Date now = new Date();
        if (log == null) {
            throw new BaseRuntimeException("点赞记录不存在");
        } else {
            if (Constants.Globals.GLOBALS_NO.equals(log.getState())) {
                throw new BaseRuntimeException("请勿重复提交");
            }
        }
        log.setState(0);
        log.setUpdateTime(now);
        trialReportLikeLogMapper.updateByPrimaryKeySelective(log);


        //点赞数量 自减
        WmActivityFreeTrialLogDao.dao().incrLikeCount(freeTrialLog.getGuid(), -1);

        return new BeanCommonResult();
    }

参考文章
SpringBoot中使用Aspect实现切面，超详细
@Aspect 注解使用详解
如何实现自定义注解