CompletionService 使用场景

	// 根据业务入参获取业务执行的beanId
			List<String> beanIdList = getBeanIdList(infoTypeList);
			Map<String, Object> resultMap = new HashMap<>();
			int size = beanIdList.size();
            final CountDownLatch latch = new CountDownLatch(size);
            List<Future<Map<String, Object>>> futureTaskList = new ArrayList<>(size);
            ExecutorService executorService = Executors.newFixedThreadPool(size);
            CompletionService<Map<String, Object>> completionService = new ExecutorCompletionService(executorService);
            /**并行查询开始**/
            for (int i = 0; i < size; i++) {
                final String beanId = beanIdList.get(i);
                futureTaskList.add(completionService.submit(new Callable<Map<String, Object>>() {
                    @Override
                    public Map<String, Object> call() {
                        Map<String, Object> tempMap = new HashMap<>();
                        try {
                            tempMap.putAll(((QueryService) SpringContextUtil.getBean(beanId)).query(paramMap));
                            latch.countDown();
                        } catch (BeansException e) {
                            latch.countDown();
                        }
                        return tempMap;
                    }
                }));
            }
			// 等待所有任务执行完成		
            latch.await();
            /**并行查询结束**/
            for (Future<Map<String, Object>> mapFuture : futureTaskList) {
                resultMap.putAll(mapFuture.get());
            }
			
			/**/ 阻塞获取任务结果可以去掉CountDownLatch
			for (Future<Map<String, Object>> mapFuture : futureTaskList) {
                resultMap.putAll(completionService.take().get());
            }*/