Firebase Admin SDK 5.0.0, setCredentials cannot resolve ** Java ** method

This is done through a servlet module using Android Studio 2.3.2

private FirebaseApp app = null; // To avoid NullPointerExeception
private FirebaseDatabase database = FirebaseDatabase.getInstance(); // the error points here: FirebaseApp with name [DEFAULT] doesn't exist.
private DatabaseReference myRef = database.getReference("table/ID"); //Table from Firebase

      

        
        
        
      

    

It's inside the Get method, and I only want to read the value (plain). My problem is with setCredential, it just says "cannot resolve method"

I ended up in the backend gradle file:

appengineSdk 'com.google.appengine:appengine-java-sdk:1.9.34'
compile 'com.google.appengine:appengine-api-1.0-sdk:1.9.53'
compile 'org.apache.httpcomponents:httpclient:4.5.3'
compile 'javax.servlet:servlet-api:2.5'
compile 'com.google.firebase:firebase-server-sdk:3.0.3'
compile 'com.google.firebase:firebase-admin:5.0.0'

      

        
        
        
      

    

I tried a few different ways to implement the credentials, as you can see that they are "// commented out" .

Only one of them works with SDK 4+ admin "setServiceAccount" is deprecated today if I compile and deploy it to App Engine and then Firebase wants to read a table that says: java.lang.IllegalStateException: FirebaseApp named [DEFAULT] not exist.

So, I have two options ( I am open to hear everything from you ):

• setCredentials doesn't work.

• setServiceAccount compiles but doesn't work

  InputStream serviceAccount = this.getClass().getResourceAsStream("/WEB-INF/YourJsonFile.json"); //JsonFile from Account Services 
  FirebaseOptions options = new FirebaseOptions.Builder()
      .setCredential(FirebaseCredentials.fromCertificate(serviceAccount)) // example (doesn't compile)
    //.setCredential(FirebaseCredentials.applicationDefault()) //same problem (doesn't compile)
    //.setServiceAccount(serviceAccount)                    //compiling & it throws the error: FirebaseApp with name [DEFAULT] doesn't exist.
      .setDatabaseUrl("https://YourDatabaseName.firebaseio.com")
      .build();
  this.app = FirebaseApp.initializeApp(options);
  
        
  
          
          
          
        
  
      

And I call myRef to read a value like this:

     myRef.addListenerForSingleValueEvent(new ValueEventListener() {

      

        
        
        
      

    

When I run the app it tells me the line FirebaseDatabase.getInstance (by attributes)

thank