firebase-database Getting started with firebase-database Automatically map custom model to data structure

Example

After you have set a few data to database and have get a structure consisting of several nodes like this;

"user" : {
    "-KdbKcU2ptfYF2xKb5aO" : {
      "firstName" : "Arthur",
      "lastName" : "Schopenhauer",
      "userName" : "AphorismMan",
      "phone" : "+9022-02-1778",
      "gender": "M",
      "age" : 25
    },
    "-KdbQFjs9BDviuqQVHjY" : {
      "firstName" : "Werner",
      "lastName" : "Heisenberg",
      "userName" : "whereAmI",
      "phone" : "+9005-12-1901",
      "gender": "M",
      "age" : 75
    }
  }

you can categorize data structures.

Creating Class

Create a model class to set to database.

@IgnoreExtraProperties
public class User {
    public String firstName;
    public String lastName;
    public String userName;
    public String phone;
    public String gender;
    public int age;

    public User() {
    }

    public User(String firstName, String lastName, String userName, String phone, String gender, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.userName = userName;
        this.phone = phone;
        this.gender = gender;
        this.age = age;
    }
}

Some things to remember when creating a model class that you want to map to your data:

1. You have to have an empty constructor
2. Scope of Variables/Fields must be public, so that the DataSnapshot returning from the firebase can access these fields. If you don't do that, when you want to get data, DataSnapshot can't access to your model in callback and that will cause an exception.
3. Names of Variables/Fields should match to those in your data structure.

Sending to Firebase

Create a User object

User user = new User ( "Arthur","Schopenhauer","AphorismMan","+9022-02-1778","M",25)

and reference

DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();

Now you have the reference of your database. Create an user node with databaseReference.child("user"). If you do .push() your models will locate under randomly created unique ids like above, "-KdbKcU2ptfYF2xKb5aO", "-KdbQFjs9BDviuqQVHjY".

databaseReference.child("user").push().setValue(user, new DatabaseReference.CompletionListener() {
            @Override
            public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
                Toast.makeText(getActivity(), "User added.", Toast.LENGTH_SHORT).show();

            }
        });

If you want to set your datas under your specific key, do it with .child("yourSpecificKey") instead of .push().

databaseReference.child("user").child("yourSpecificKey").setValue(user,...