为什么Firebase Java SDK设置后无法终止? [英] Why Firebase Java SDK can't terminate after set?

问题描述

我想构建一个简单的应用程序，以将Firebase数据库中的某些键设置为某个值.因为它是异步的，所以我创建了CountDownLatch并等待它完成，但是它从未完成.

I want to build simple app that sets some key in a firebase database to some value. Because it is async, I create CountDownLatch and wait for it to complete, but it never completes.

这是我的代码:

package me.ibrohim.adler;

import com.google.firebase.FirebaseApp;
import com.google.firebase.FirebaseOptions;
import com.google.firebase.auth.FirebaseCredentials;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.tasks.OnCompleteListener;
import com.google.firebase.tasks.Task;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.function.Consumer;

public class Main {

    public static void main(String [] args) throws InterruptedException {

        FileInputStream serviceAccount = null;

        try {

            serviceAccount = new FileInputStream("/home/ibrohim/.adler/adminsdk.json");

            FirebaseOptions options = new FirebaseOptions.Builder()
                    .setCredential(FirebaseCredentials.fromCertificate(serviceAccount))
                    .setDatabaseUrl("https://[my app].firebaseio.com/")
                    .build();

            FirebaseApp.initializeApp(options);

        } catch (IOException e) {

            e.printStackTrace();

        } finally {

            if (serviceAccount != null) try {

                serviceAccount.close();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }


        CountDownLatch done = new CountDownLatch(1);

//        new Thread(() -> {
//            try {
//                Thread.sleep(1000);
//                done.countDown();
//            }
//            catch (Exception e){
//                System.err.println(e);
//            }
//        }).start();

        FirebaseDatabase
                .getInstance()
                .getReference("[some path]")
                .setValue("[some value]")
                .addOnCompleteListener(task -> done.countDown());

        done.await();

    }

}

推荐答案

我刚刚在IntelliJ中运行了这段代码:

I just ran this code in IntelliJ:

CountDownLatch done = new CountDownLatch(1);
database.getReference("45253891").setValue("[some value]")
        .addOnCompleteListener(task -> done.countDown());
done.await();

它运行起来没有任何问题. (请参见结果此处)

And it ran without any problem. (see the result here)

我不确定您系统中正在发生什么.您确定能打到setValue()电话吗?

I'm not sure what's going on in your system. Are you sure you reach the setValue() call?

更新:Doug Stevenson在评论中展示了如何确保完成后退出JVM:

Update: in the comments Doug Stevenson shows how you can ensure the JVM exits when you're done:

我通常在等待之后添加System.exit(0)，以在知道完成后强制停止操作.

I typically add System.exit(0) after the await to force things to stop when I know they're done.

因此，它使用CountDownLatch或类似的同步原语，但在其后添加System.exit(0).

So this uses a CountDownLatch or similar synchronization primitive like above, but then adds a System.exit(0) after it.

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