如何使用Java(桌面)将数据保存到Firebase [英] How to save data to Firebase using Java (Desktop)
问题描述
我正在尝试使用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，我一直在这里查看提供的文档:
出于测试目的，目前规则已设置为公开.
更新:
尝试了FrankvanPuffelen的评论后，我仍然无法保存或读取Firebase中的数据.我为测试目的编写了一个更简单的代码.这是代码:
公共类Main {私有静态最终字符串DATABASE_URL ="https://sems-firebase.firebaseio.com/";私有静态DatabaseReference数据库；私人静态布尔完成=假;公共静态无效startListeners(){database.child("posts").addValueEventListener(new ValueEventListener(){@Override公共无效onDataChange(DataSnapshot dataSnapshot){发布post = dataSnapshot.getValue(Post.class);System.out.println(post);完成=真；}@Override公共无效onCancelled(DatabaseError databaseError){System.out.println(读取失败:" + databaseError.getCode());}});while(！完成);}公共静态void main(String [] args)抛出FileNotFoundException {尝试 {FileInputStream serviceAccount = new FileInputStream("sems-firebase.json");FirebaseOptions选项=新的FirebaseOptions.Builder().setCredentials(GoogleCredentials.fromStream(serviceAccount)).setDatabaseUrl(DATABASE_URL).建造();FirebaseApp defaultApp = FirebaseApp.initializeApp(options);FirebaseDatabase defaultDatabase = FirebaseDatabase.getInstance(defaultApp);System.out.println(defaultDatabase.getReference().toString());} catch(IOException e){System.out.println(错误:无效的服务帐户凭据.请参阅自述文件.");System.out.println(e.getMessage());System.exit(1);}//共享数据库参考数据库= FirebaseDatabase.getInstance().getReference();//开始监听数据库startListeners();} }
所以我一直在做的是，我运行代码，然后转到数据库url并手动编辑帖子，我希望得到我刚刚在控制台上编辑过的帖子的打印件，但是什么也没发生./p>
这是数据库的快照:
更新2
我相信这里提出的建议:
我试图对此进行修改:
公共静态void startListeners()抛出InterruptedException {DatabaseReference数据库= FirebaseDatabase.getInstance().getReference("posts/adad2131/author");CountDownLatch完成=新的CountDownLatch(1);database.setValue("Test"，新的DatabaseReference.CompletionListener(){@Override公共无效onComplete(DatabaseError de，DatabaseReference dr){done.countDown();}});done.await();} 但是onComplete方法永远不会执行，程序永远也不会完成.至于这里提出的建议:
更新3
因此，我已简化代码以简化使用.为了确保我从项目的服务帐户面板中生成了一个新的私钥，这是我初始化应用程序的方式:
尝试{FileInputStream serviceAccount = new FileInputStream("sems-firebase-firebase-adminsdk-gamnp-874087bbd1.json");FirebaseOptions选项=新的FirebaseOptions.Builder().setCredentials(GoogleCredentials.fromStream(serviceAccount)).setDatabaseUrl("https://sems-firebase.firebaseio.com/").建造();FirebaseApp.initializeApp(options);} catch(IOException e){System.out.println(错误:无效的服务帐户凭据.");System.out.println(e.getMessage());System.exit(1);} 这是数据库的快照，我要更改的值是ID为"adad2131"的帖子的author字段.
我尝试使用"posts/adad2131/author"，"/posts/adad2131/author"或只是"adad2131/author"引用该字段，也许我在引用错误吗?
这是完整的代码:
公共类Main {公共静态void main(String [] args)抛出FileNotFoundException，InterruptedException {尝试 {FileInputStream serviceAccount = new FileInputStream("sems-firebase-firebase-adminsdk-gamnp-874087bbd1.json");FirebaseOptions选项=新的FirebaseOptions.Builder().setCredentials(GoogleCredentials.fromStream(serviceAccount)).setDatabaseUrl("https://sems-firebase.firebaseio.com/").建造();FirebaseApp.initializeApp(options);} catch(IOException e){System.out.println(错误:无效的服务帐户凭据.");System.out.println(e.getMessage());System.exit(1);}//尝试更改Firebase中的数据CountDownLatch完成=新的CountDownLatch(1);FirebaseDatabase.getInstance().getReference("posts/adad2131/author").setValue("Test"，新的DatabaseReference.CompletionListener(){@Override公共无效onComplete(DatabaseError de，DatabaseReference dr){done.countDown();}});done.await();}} Ps.我也在使用admin sdk 5.9
我刚刚使用Firebase Admin SDK 5.9将您的代码复制到了一个项目中并运行了该代码，然后将其毫无问题地写入了数据库.
CountDownLatch完成=新的CountDownLatch(1);FirebaseDatabase.getInstance().getReference("49723347").setValue("Test"，新的DatabaseReference.CompletionListener(){@Override公共无效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
参考 49723347 是我数据库中的路径(这是您问题的ID).我没有进行其他更改.
所以看来问题出在我们一直关注的代码中.这是我初始化应用程序的方式:
FileInputStream serviceAccount = new FileInputStream("stackoverflow-3d9889aaeddb.json");FirebaseOptions选项=新的FirebaseOptions.Builder().setCredential(FirebaseCredentials.fromCertificate(serviceAccount)).setDatabaseUrl("https://stackoverflow.firebaseio.com/").建造();FirebaseApp.initializeApp(options); 您确定配置是针对您要编写的项目的吗?
I'm trying to save data to Firebase using a desktop application written in Java. However, for some reason it doesn't work, I've been folowing the documentation provided here: https://firebase.google.com/docs/database/admin/save-data. Couldn't find any video tutorials on the matter, all videos are web or mobile related. Basically I want to create an object called Venda that has 3 attributes (ID, data, valor) and then save it on Firebase. Thank you!
Here is the main method:
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 connection:
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();
}
}
Venda class:
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;
}
}
The database info:
For now the rules are set to public, for testing purposes.
UPDATE:
Alright after trying what was proposed on FrankvanPuffelen's comment I'm still not able to save or read data from Firebase. I made a simpler code for testing purposes. Here is the code:
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();
}
}
So what I've been doing is, I run the code and then go to the database url and manually edit a post, I expect to get a print of the post I just edited on the console, but nothing happens.
Here is a snapshot of the database:
UPDATE 2
I believe what was proposed here: Why Firebase Java SDK can't terminate after set? is deprecated, because if I try the code looks like this:
I tried modifying that to this:
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();
}
But the onComplete method never gets executed and the programs never finishes. As for what was proposed here: java Firebase: delay exit until writes finish may also be deprecated as it seems the CompletionListener() no longer lives inside Firebase, but I could find it inside DatabaseReference, so I modified the code to this:
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());
}
Like before, the onComplete method never gets executed and the program never finishes or set the data in the database. Here is a snapshot of the post I'm trying to modify:
UPDATE 3
So I've simplified the code for ease of use. Just to be sure I generated a new private key from the project's service account pannel, here is how I initialize the app:
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);
}
Here is a snapshot of the database, the value I'm trying to change is the author field of post with id "adad2131".
I've tried referencing that field with "posts/adad2131/author", "/posts/adad2131/author" or simply "adad2131/author", maybe I'm referencing it wrong?
Here is the full code:
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();
}
}
Ps. I'm also using admin sdk 5.9
I just copied your code into a project using Firebase Admin SDK 5.9 and ran it, and it wrote to the database without problems.
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();
You can see the result here: https://stackoverflow.firebaseio.com/49723347.json
The reference 49723347 is the path in my database (it's the ID of your question). I made no other changes.
So it seems that the problem is not in the code we've been looking at. Here's how I initialize the app:
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);
Are you sure the configuration is for the project you're trying to write?
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