java - 如何使用 Java 将数据保存到 Firebase(桌面)

Question

我正在尝试使用用 Java 编写的桌面应用程序将数据保存到 Firebase。但是，由于某种原因它不起作用，我一直在遵循此处提供的文档:https://firebase.google.com/docs/database/admin/save-data 。找不到任何有关此事的视频教程，所有视频都与网络或移动设备相关。基本上我想创建一个名为 Venda 的对象，它有 3 个属性(ID、数据、valor)，然后将其保存在 Firebase 上。谢谢!

主要方法如下:

public class Main {

    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("--------- Begin of Output ---------");
        Firebase firebase = new Firebase();
        VendasCRUD venda = new VendasCRUD(firebase);
        venda.createVenda(new Venda(0, "23/05/1993", 45.67));
        System.out.println("----------- End of Output -----------");
    }

}

Firebase 连接:

public class Firebase {

    public Firebase() throws FileNotFoundException, IOException {
        FileInputStream serviceAccount = new FileInputStream("C:\\Users\\Alex\\Documents\\NetBeansProjects\\SEMS\\src\\main\\java\\br\\com\\sems\\firebase\\sems-firebase.json");

        FirebaseOptions options = new FirebaseOptions.Builder()
                .setCredentials(GoogleCredentials.fromStream(serviceAccount))
                .setDatabaseUrl("https://sems-firebase.firebaseio.com/")
                .build();

        FirebaseApp.initializeApp(options);
    }

    public DatabaseReference getDataBaseReference() {
        return FirebaseDatabase.getInstance().getReference();
    }

}

文达级:

public class Venda {

    public int ID;
    public String data;
    public double valor;

    public Venda(int ID, String data, double valor) {
        this.ID = ID;
        this.data = data;
        this.valor = valor;
    }

    @Override
    public String toString() {
        return ID + "," + data + "," + valor;
    }

}

数据库信息:

目前，出于测试目的，规则设置为公开。

<小时/>

更新:

好吧，在尝试了 FrankvanPuffelen 评论中的建议后，我仍然无法从 Firebase 保存或读取数据。我出于测试目的编写了一个更简单的代码。这是代码:

public class Main {

    private static final String DATABASE_URL = "https://sems-firebase.firebaseio.com/";
    private static DatabaseReference database;
    private static boolean finished = false;

    public static void startListeners() {
        database.child("posts").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                Post post = dataSnapshot.getValue(Post.class);
                System.out.println(post);
                finished = true;
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                System.out.println("The read failed: " + databaseError.getCode());
            }
        });
        while(!finished);
    }

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

        try {
            FileInputStream serviceAccount = new FileInputStream("sems-firebase.json");
            FirebaseOptions options = new FirebaseOptions.Builder()
                    .setCredentials(GoogleCredentials.fromStream(serviceAccount))
                    .setDatabaseUrl(DATABASE_URL)
                    .build();



        FirebaseApp defaultApp =  FirebaseApp.initializeApp(options);
        FirebaseDatabase defaultDatabase = FirebaseDatabase.getInstance(defaultApp);

        System.out.println(defaultDatabase.getReference().toString());

    } catch (IOException e) {
        System.out.println("ERROR: invalid service account credentials. See README.");
        System.out.println(e.getMessage());

        System.exit(1);
    }

    // Shared Database reference
    database = FirebaseDatabase.getInstance().getReference();

    // Start listening to the Database
    startListeners();

}

}

所以我一直在做的是，我运行代码，然后转到数据库网址并手动编辑帖子，我希望得到我刚刚在控制台上编辑的帖子的打印，但没有任何反应。

这是数据库的快照:

<小时/>

更新2

我相信这里提出的建议:Why Firebase Java SDK can't terminate after set?已弃用，因为如果我尝试代码如下所示:

我尝试将其修改为:

public static void startListeners() throws InterruptedException {
    DatabaseReference database = FirebaseDatabase.getInstance().getReference("posts/adad2131/author");
    CountDownLatch done = new CountDownLatch(1);
    database.setValue("Test", new DatabaseReference.CompletionListener() {
        @Override
        public void onComplete(DatabaseError de, DatabaseReference dr) {
            done.countDown();
        }
    });
    done.await();
}

但是 onComplete 方法永远不会被执行，程序也永远不会完成。至于这里提出的建议:java Firebase: delay exit until writes finish也可能已被弃用，因为 CompletionListener() 似乎不再存在于 Firebase 中，但我可以在 DatabaseReference 中找到它，因此我将代码修改为:

private static final String DATABASE_URL = "https://sems-firebase.firebaseio.com/";

public static void startListeners() throws InterruptedException {
    DatabaseReference database = FirebaseDatabase.getInstance().getReference("posts/adad2131/author");
    final AtomicBoolean done = new AtomicBoolean(false);
    database.setValue("Test", new DatabaseReference.CompletionListener() {
        @Override
        public void onComplete(DatabaseError de, DatabaseReference dr) {
            done.set(true);
        }
    });
    while (!done.get());
}

像以前一样，onComplete 方法永远不会被执行，程序也永远不会完成或在数据库中设置数据。这是我尝试修改的帖子的快照:

<小时/>

更新3

所以我简化了代码以方便使用。为了确保我从项目的服务帐户面板生成了新的私钥，以下是我初始化应用程序的方法:

    try {
        FileInputStream serviceAccount = new FileInputStream("sems-firebase-firebase-adminsdk-gamnp-874087bbd1.json");
        FirebaseOptions options = new FirebaseOptions.Builder()
                .setCredentials(GoogleCredentials.fromStream(serviceAccount))
                .setDatabaseUrl("https://sems-firebase.firebaseio.com/")
                .build();

        FirebaseApp.initializeApp(options);

    } catch (IOException e) {
        System.out.println("ERROR: invalid service account credentials.");
        System.out.println(e.getMessage());

        System.exit(1);
    }

这是数据库的快照，我试图更改的值是 ID 为“adad2131”的帖子的作者字段。

我尝试使用“posts/adad2131/author”、“/posts/adad2131/author”或简单的“adad2131/author”引用该字段，也许我引用错了？

完整代码如下:

public class Main {

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

        try {
            FileInputStream serviceAccount = new FileInputStream("sems-firebase-firebase-adminsdk-gamnp-874087bbd1.json");
            FirebaseOptions options = new FirebaseOptions.Builder()
                    .setCredentials(GoogleCredentials.fromStream(serviceAccount))
                    .setDatabaseUrl("https://sems-firebase.firebaseio.com/")
                    .build();

            FirebaseApp.initializeApp(options);

        } catch (IOException e) {
            System.out.println("ERROR: invalid service account credentials.");
            System.out.println(e.getMessage());

            System.exit(1);
        }

        //Try to change data in Firebase
        CountDownLatch done = new CountDownLatch(1);
        FirebaseDatabase.getInstance().getReference("posts/adad2131/author").setValue("Test", new DatabaseReference.CompletionListener() {
            @Override
            public void onComplete(DatabaseError de, DatabaseReference dr) {
                done.countDown();
            }
        });
        done.await();

    }
}

诗。我也在使用 admin sdk 5.9

Answer 1

我刚刚使用 Firebase Admin SDK 5.9 将您的代码复制到项目中并运行它，它写入数据库时​​没有出现任何问题。

CountDownLatch done = new CountDownLatch(1);
FirebaseDatabase.getInstance().getReference("49723347").setValue("Test", new DatabaseReference.CompletionListener() {
    @Override
    public void onComplete(DatabaseError de, DatabaseReference dr) {
        done.countDown();
    }
});
done.await();

您可以在此处查看结果:https://stackoverflow.firebaseio.com/49723347.json

引用49723347是我数据库中的路径(它是您的问题的ID)。我没有做任何其他更改。

看来问题不在我们一直在查看的代码中。以下是我初始化应用程序的方法:

FileInputStream serviceAccount = new FileInputStream("stackoverflow-3d9889aaeddb.json");

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

FirebaseApp.initializeApp(options);

您确定该配置适合您要编写的项目吗？