如何使用Java程序将数据写入firebase

我正在尝试将数据写入现有的Firebase数据库，但没有写入数据。

是否有一个示例Java程序将数据写入某个Firebase数据库，我可以使用它？

我所做的就是以下内容：

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 users = new HashMap(); users.put("A", "Jaap"); System.out.println(users); db.setValue(users); System.out.println(db); } 

}

‘testdata’是数据库根目录下的现有子节点。

第二版计划

 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."); } } }); 

它会停止并显示以下消息：

 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

请注意

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

哪些没有记录。

以下课程有效。

 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(); } }