Java多線程實戰

private static ThreadPoolExecutor service = new ThreadPoolExecutor(50, 200,
            30L, TimeUnit.MINUTES,
            new LinkedBlockingQueue<Runnable>());

    private static ConcurrentHashMap<Long, Future<Zuji2YearCongratulationDto>> futures = new ConcurrentHashMap<Long, Future<Zuji2YearCongratulationDto>>();

    @Override
    public Zuji2YearCongratulationDto getUserData(final long uid) {
        final int ttl = 20 * 60;
        final String key = "zuji2year:" + uid;
        //嘗試從緩存中取
        Zuji2YearCongratulationDto dto = getZuji2YearCongratulationDtoFromCache(key);
        if (dto != null) {
            return dto;
        }

        LogDto logDto = new LogDto();
        logDto.setPath("db");
        logDto.setActiveThreadCountBefore(service.getActiveCount());
        logDto.setQueueCountBefore(service.getQueue().size());
        logDto.setCompleteCountBefore(service.getCompletedTaskCount());
        logDto.setLargestPoolSizeBefore(service.getLargestPoolSize());


        Future<Zuji2YearCongratulationDto> future = futures.get(uid);

        //判斷是否在隊列中
        if (future == null) {
            //若是再也不隊列中，則加入取數據的隊列
            future = service.submit(new Callable<Zuji2YearCongratulationDto>() {
                @Override
                public Zuji2YearCongratulationDto call() throws Exception {
                    Zuji2YearCongratulationDto dto = getZuji2YearCongratulationDtoFromCache(key);
                    if (dto == null) {
                        dto = getZuji2YearCongratulationDto(uid);
                        jedisTemplate.setex(key, new JsonSerializer().serialize(dto), ttl);
                    }
                    return dto;
                }
            });
            futures.put(uid, future);
        }

        //加入隊列之後，每隔100ms判斷是否取到了數據，最多判斷100次，也就是最多等待10s
        int tryCount = 0;
        while (!future.isDone() && tryCount++ < 100) {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {

            }
        }


        try {
            dto = future.get(1, TimeUnit.SECONDS);
            if (dto != null) {
                futures.remove(uid);
            }
        } catch (Exception e) {
        }

        logDto.setActiveThreadCountAfter(service.getActiveCount());
        logDto.setQueueCountAfter(service.getQueue().size());
        logDto.setCompleteCountAfter(service.getCompletedTaskCount());
        logDto.setLargestPoolSizeAfter(service.getLargestPoolSize());
        logDto.setEndTime(System.currentTimeMillis());
        log.info(new JsonSerializer().serialize(logDto));
        return dto;
    }