java Firebase：延迟退出直到写入完成 [英] java Firebase: delay exit until writes finish

问题描述

我有一个用Java编写的服务器，它可以在监听，处理和更新Firebase数据时接收关闭信号。由于Firebase线程是Java中的守护线程，我想为主线程添加一些延迟，以允许写操作完成。

I have a server written in Java that can receive a shut down signal while it's listening to, processing, and updating Firebase data. Since the Firebase threads are daemon threads in Java, I wanted to add some delay to the main thread to allow write operations to complete.

我当前的想法是锁存方法：使用一些并发计数器来跟踪挂起的写操作，并让主线程退出时没有。计数器将在 onComplete（）回调中更新，所以我想知道：

My current idea is the latch approach: use some concurrent counter to track pending writing operations, and let the main thread exit when there are none. The counter would get updated in onComplete() callbacks, so I was wondering:

在Firebase客户端，可能 onComplete（）回调永远不会被调用？是否有合理的死锁危险？

In the Firebase client, when might onComplete() callbacks never get called? Is there reasonable danger of deadlock?

推荐答案

取自这个google群组讨论。这使用布尔 done （在这种情况下为线程安全操作的AtomicBoolean）和 while 循环。 >

Taken from this google group discussion. This uses a boolean done (an AtomicBoolean for thread safe ops in this case) and a while loop.

import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;

import java.util.Date;
import java.util.concurrent.atomic.AtomicBoolean;

public class Demo {

    public static void main(String[] args) {
        final AtomicBoolean done = new AtomicBoolean(false);
        Firebase ref = new Firebase("https://testjava.firebaseio-demo.com/");
        ref.setValue(new Date().toString(), new Firebase.CompletionListener() {
            @Override
            public void onComplete(FirebaseError firebaseError, Firebase firebase) {
                done.set(true);
            }
        });
        while (!done.get());
    }
}

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