从Java线程返回值 [英] Return values from Java Threads

问题描述

我有一个Java线程如下：

I have a Java Thread like the following:

   public class MyThread extends Thread {
        MyService service;
        String id;
        public MyThread(String id) {
            this.id = node;
        }
        public void run() {
            User user = service.getUser(id)
        }
    }

我有大约300个id，每几秒钟 - 我启动线程来调用每个id。例如

I have about 300 ids, and every couple of seconds - I fire up threads to make a call for each of the id. Eg.

for(String id: ids) {
    MyThread thread = new MyThread(id);
    thread.start();
}

现在，我想从每个线程收集结果，批处理插入数据库，而不是每2秒进行300个数据库插入。

Now, I would like to collect the results from each threads, and do a batch insert to the database, instead of making 300 database inserts every 2 seconds.

任何想法我如何能做到这一点。

Any idea how I can accomplish this?

推荐答案

如果要在进行数据库更新之前收集所有结果，可以使用 invokeAll 方法。这会照顾您在一次提交任务时需要的记帐，例如 daveb 建议。

If you want to collect all of the results before doing the database update, you can use the invokeAll method. This takes care of the bookkeeping that would be required if you submit tasks one at a time, like daveb suggests.

private static final ExecutorService workers = Executors.newCachedThreadPool();

...

Collection<Callable<User>> tasks = new ArrayList<Callable<User>>();
for (final String id : ids) {
  tasks.add(new Callable<User>()
  {

    public User call()
      throws Exception
    {
      return svc.getUser(id);
    }

  });
}
/* invokeAll blocks until all service requests complete, 
 * or a max of 10 seconds. */
List<Future<User>> results = workers.invokeAll(tasks, 10, TimeUnit.SECONDS);
for (Future<User> f : results) {
  User user = f.get();
  /* Add user to batch update. */
  ...
}
/* Commit batch. */
...

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