线程池的使用示例-批量查询

1.使用countDown

 1 public Map<Long, User> batchQueryUserInfo(List<Long> userIds) {
 2     List<List<Long>> userIdPartitions = Lists.partition(userIds, 50);
 3     List<User> userList = new ArrayList<>();
 4 
 5     CountDownLatch latch = new CountDownLatch(userIdPartitions.size());
 6     userIdPartitions.forEach(userIdsPartition -> {
 7         executorService.submit(()->{
 8             try {
 9                 List<User> userInfoList = userService.batchQuery(userIdsPartition.stream().map(String::valueOf).collect(Collectors.toList()));
10                 userList.addAll(userInfoList);
11             } catch (Exception e) {
12                 //log
13                 return;
14             } finally {
15                 latch.countDown();
16             }
17         });
18     });
19     try {
20         latch.await(1, TimeUnit.SECONDS);
21     } catch (Exception e) {
22         //log
23     }
24     return userList.stream().collect(Collectors.toMap(user -> Long.parseLong(user.getUserId()), v->v));
25 }

2.Future.get

future.get方法会阻塞，效率不如CountDownLatch。

 1 public Map<Long, User> batchQueryUserInfo(List<Long> empIds) {
 2     List<List<Long>> userIdPartitions = Lists.partition(userIds, 50);
 3     List<User> userList = new ArrayList<>();
 4 
 5     List<Future<List<User>>> futureList = new ArrayList<>();
 6     userIdPartitions.forEach(userIdsPartition -> {
 7         Future<List<User>> future = executorService.submit(() -> {
 8             List<User> userInfoList = null;
 9             try {
10                 userInfoList = userService.batchQuery(userIdsPartition.stream().map(String::valueOf).collect(Collectors.toList()));
11             } catch (Exception e) {
12                 //log
13             }
14             return userInfoList;
15         });
16         futureList.add(future);
17 
18     });
19     long timeLimit = 1;
20     for (Future<List<User>> future : futureList) {
21         try {
22             userList.addAll(future.get(timeLimit, TimeUnit.MILLISECONDS));
23         } catch (Exception e) {
24             //log
25         }
26     }
27     return userList.stream().collect(Collectors.toMap(user -> Long.parseLong(user.getUserId()), v->v));
28 }