Javaプログラムでfirebaseにデータを書き込む方法

Question

既存のFirebaseデータベースにデータを書き込もうとしていますが、データは書き込まれません。

Firebaseデータベースにデータを書き込むJavaプログラムの例がありますか？私はSOFARを行っていることは以下の通りです

：

package org.nilostep.bota.dcp.export; 

import com.google.firebase.FirebaseApp; 
import com.google.firebase.FirebaseOptions; 
import com.google.firebase.auth.FirebaseCredentials; 
import com.google.firebase.database.*; 

import java.io.FileInputStream; 
import java.util.HashMap; 
import java.util.Map; 

public class ReadWriteFirebase { 

    private static final String DATABASE_URL = " (the url of my database) "; 


    public static void main(String[] args) throws Exception { 
    FileInputStream serviceAccount = 
      new FileInputStream("bota-6e0b33e3f1fe.json"); 

    FirebaseOptions options = new FirebaseOptions.Builder().setCredential(FirebaseCredentials.fromCertificate(serviceAccount)).setDatabaseUrl("https://bota-313fb.firebaseio.com").build(); 

    FirebaseApp.initializeApp(options); 

    DatabaseReference db = FirebaseDatabase.getInstance().getReference().child("testdata"); 

    Map<String, String> users = new HashMap<>(); 
    users.put("A", "Jaap"); 
    System.out.println(users); 
    db.setValue(users); 

    System.out.println(db); 
} 

}

'テストデータは、' データベース・ルート下の既存の子です。

プログラムの第2のバージョン

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

    FileInputStream serviceAccount = 
      new FileInputStream("bota-6e0b33e3f1fe.json"); 

    FirebaseOptions options = new FirebaseOptions.Builder() 
      .setCredential(FirebaseCredentials.fromCertificate(serviceAccount)) 
      .setDatabaseUrl(DATABASE_URL) 
      .build(); 

    FirebaseApp.initializeApp(options); 

    FirebaseDatabase db = FirebaseDatabase.getInstance(DATABASE_URL); 
    DatabaseReference ref = db.getReference().child("testdata"); 
    ref.setValueAsync("I'm writing data", new DatabaseReference.CompletionListener() { 
     @Override 
     public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) { 
      if (databaseError != null) { 
       System.out.println("Data could not be saved " + databaseError.getMessage()); 
      } else { 
       System.out.println("Data saved successfully."); 
      } 
     } 
    }); 

それは次のメッセージで停止：

Exception in thread "main" com.google.firebase.database.DatabaseException: Failed to parse node with class class org.nilostep.bota.dcp.export.ReadWriteFirebase$1 
at com.google.firebase.database.snapshot.NodeUtilities.NodeFromJSON(NodeUtilities.java:108) 
at com.google.firebase.database.snapshot.NodeUtilities.NodeFromJSON(NodeUtilities.java:33) 
at com.google.firebase.database.snapshot.PriorityUtilities.parsePriority(PriorityUtilities.java:38) 
at com.google.firebase.database.DatabaseReference.setValue(DatabaseReference.java:241) 
at com.google.firebase.database.DatabaseReference.setValueAsync(DatabaseReference.java:218) 
at org.nilostep.bota.dcp.export.ReadWriteFirebase.main(ReadWriteFirebase.java:44) 

Answer 1

注記載されていません

CountDownLatch, 
latch.countdown(), 
latch.await() 

を。

次のクラスが機能します。

import com.google.auth.oauth2.GoogleCredentials; 
import com.google.firebase.FirebaseApp; 
import com.google.firebase.FirebaseOptions; 
import com.google.firebase.database.DatabaseError; 
import com.google.firebase.database.DatabaseReference; 
import com.google.firebase.database.FirebaseDatabase; 

import java.io.IOException; 
import java.io.InputStream; 
import java.util.concurrent.CountDownLatch; 

public class Firebase { 

    private static final String DATABASE_URL = "YOUR_DB_URL"; 
    private FirebaseDatabase firebaseDatabase; 

    public Firebase() { 
     InputStream serviceAccount = this.getClass().getResourceAsStream("/bota-6e0b33e3f1fe.json"); 

     try { 
      FirebaseOptions options = new FirebaseOptions.Builder() 
       .setCredentials(GoogleCredentials.fromStream(serviceAccount)) 
       .setDatabaseUrl(DATABASE_URL) 
       .build(); 
      FirebaseApp.initializeApp(options); 
      firebaseDatabase = FirebaseDatabase.getInstance(DATABASE_URL); 

     } catch (IOException ioe) { 
      System.out.println(ioe.getMessage()); 
     } 
    } 

    public void update(Object value) { 
     update(value, "testdata"); 
    } 

    public void update(Object value, String key) { 
     try { 
      DatabaseReference ref = firebaseDatabase.getReference(key); 
      final CountDownLatch latch = new CountDownLatch(1); 
      ref.setValue(value, new DatabaseReference.CompletionListener() { 
       @Override 
       public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) { 
        if (databaseError != null) { 
         System.out.println("Data could not be saved " + databaseError.getMessage()); 
         latch.countDown(); 
        } else { 
         System.out.println("Data saved successfully."); 
         latch.countDown(); 
        } 
       } 
      }); 
      latch.await(); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 
    } 

    public void close() { 
     firebaseDatabase.getApp().delete(); 
    } 
}