详解基于redis实现分布式锁

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface StockLock {

    /**
     * 
     * @Description 锁key的前缀
     * @Date 15:25 2020年03月25日, 0025
     * @Param []
     * @return java.lang.String
     */
    String prefix() default "";
    /**
     *
     * @Description key的分隔符
     * @Date 15:27 2020年03月25日, 0025
     * @Param []
     * @return java.lang.String
     */
    String delimiter() default ":";
}

@Target({ElementType.PARAMETER , ElementType.METHOD , ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface StockParam {
    /*
    * @Description 组成key
    * @Date 11:11 2020年03月26日, 0026
    * @Param []
    * @return java.lang.String[]
    */
    String[] names() default {""};
}

@Around("execution(public * *(..)) && @annotation(com.ay.framework.order.redis.product.StockLock)")

RedisAtomicLong entityIdCounter = new RedisAtomicLong(lockKey, redisTemplate.getConnectionFactory());
    if (redisTemplate.hasKey(CoreConstants.UPDATEPRODUCTREDISLOCKKEY + lockKey)) {
        //表示lockKey的库存信息有变动。此时无法进行交易
        throw new BusinessException("库存变动。暂无法交易");
    }
    Long increment = entityIdCounter.decrementAndGet();
    if (increment >= 0) {
        try {
            Object proceed = pjp.proceed();
        } catch (Throwable throwable) {
            //所占资源需要释放回资源池
            while (!redisLock.tryGetLock(CoreConstants.UPDATEPRODUCTREDISLOCKKEY + lockKey, "")) {

            }
            //表示lockKey的库存信息有变动。此时无法进行交易
            long l = entityIdCounter.incrementAndGet();
            if (l < 1) {
                redisTemplate.opsForValue().set(lockKey,1);
            }
            redisLock.unLock(CoreConstants.UPDATEPRODUCTREDISLOCKKEY + lockKey);
            throwable.printStackTrace();
        }
    } else {
        redisTemplate.opsForValue().set(lockKey,0);
        throw new BusinessException("库存不足！无法操作");
    }

public Boolean tryGetLock(String key , String value) {
    return tryGetLock(key, value, -1, TimeUnit.DAYS);
}
public Boolean tryGetLock(String key , String value, Integer expire) {
    return tryGetLock(key, value, expire, TimeUnit.SECONDS);
}
public Boolean tryGetLock(String key , String value, Integer expire , TimeUnit timeUnit) {
    ValueOperations operations = redisTemplate.opsForValue();
    if (operations.setIfAbsent(key, value)) {
        //说明 redis没有该key , 换言之 加锁成功  设置过期时间防止死锁
        if (expire > 0) {
            redisTemplate.expire(key, expire, timeUnit);
        }
        return true;
    }
    return false;
}

public Boolean unLock(String key) {
    return redisTemplate.delete(key);
}

@Component()
@Primary
public class StockKeyGenerator implements CacheKeyGenerator {
    @Override
    public String getLockKey(ProceedingJoinPoint pjp) {
        //获取方法签名
        MethodSignature signature = (MethodSignature) pjp.getSignature();
        Method method = signature.getMethod();
        //获取方法cacheLock注解
        StockLock stockLock = method.getAnnotation(StockLock.class);
        //获取方法参数
        Object[] args = pjp.getArgs();
        Parameter[] parameters = method.getParameters();
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < parameters.length; i++) {
            StockParam stockParam = parameters[i].getAnnotation(StockParam.class);
            Object arg = args[i];
            if (arg instanceof Map) {
                Map<String, Object> temArgMap = (Map<String, Object>) arg;
                String[] names = stockParam.names();
                for (String name : names) {
                    if (builder.length() > 0) {
                        builder.append(stockLock.delimiter());
                    }
                    builder.append(temArgMap.get(name));
                }
            }

        }
        return builder.toString();
    }
}