What is ObjectBox? It’s a standalone database that makes object persistence simple and super fast.

This tutorial will walk you through a simple note-taking app explaining how to do basic operations with ObjectBox. To just integrate ObjectBox into your project, look at the Getting Started page.

You can check out the example code from GitHub. This allows you to run the code and explore it in its entirety. It is a simple Android app for taking notes where you can add new notes by typing in some text and delete notes by clicking on an existing note.

git clone https://github.com/objectbox/objectbox-examples.git
cd objectbox-examples/android-app

git clone https://github.com/objectbox/objectbox-examples.git
cd objectbox-examples/android-app-kotlin

git clone https://github.com/objectbox/objectbox-dart.git
cd objectbox-dart/objectbox/examples/flutter/objectbox_demo

The Note entity and Box class

To begin let’s jump right into the code: among the sources the entity class:Note. It is persisted (saved) in the database and contains all data that is part of a note, like an id, note text and the creation date.

src/Note.java
@Entity
public class Note {
    
    @Id
    long id;
    
    String text;
    String comment;
    Date date;
    
    ...
}

src/Note.kt
@Entity
data class Note(
        @Id var id: Long = 0,
        var text: String? = null,
        var comment: String? = null,
        var date: Date? = null
)

lib/main.dart
@Entity()
class Note {
  int id;
  String text;
  String? comment;
  DateTime date;
​
  ...
}

In general, an ObjectBox entity is an annotated class persisted in the database with its properties. In order to extend our note or to create new entities, you simply modify or create new plain classes and annotate them with @Entity and @Id.

Inserting notes

To see how new notes are added to the database, take a look at the following code fragments. The Box<Note> provides database operations for Note objects.

NoteActivity.java
@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    notesBox = ObjectBox.get().boxFor(Note.class);
    ...
}

NoteActivity.kt
public override fun onCreate(savedInstanceState: Bundle?) {
    ...
    notesBox = ObjectBox.boxStore.boxFor()
    ...
}

lib/main.dart
class ViewModel {
  final Store _store;
  late final Box<Note> _box;
  
  ViewModel(Directory dir)
      : _store = Store(getObjectBoxModel(), directory: dir.path + '/objectbox') {
    _box = _store.box<Note>();
  }
  
  ...

When a user clicks the ADD button the method addNote() is called. There, a new Note object is created and put into the database using the Box reference:

NoteActivity.java
private void addNote() {
    ...
    Note note = new Note();
    note.setText(noteText);
    note.setComment(comment);
    note.setDate(new Date());
    notesBox.put(note);
    Log.d(App.TAG, "Inserted new note, ID: " + note.getId());
    ...
}

NoteActivity.kt
private fun addNote() {
    ...
    val note = Note(text = noteText, comment = comment, date = Date())
    notesBox.put(note)
    Log.d(App.TAG, "Inserted new note, ID: " + note.id)
    ...
}

void addNote() {
  _box.put(Note(_noteInputController.text));
}

Note that the ID property (0 when creating the Note object), is assigned by ObjectBox during put().

Removing/deleting notes

When the user taps a note, it is deleted. The Box provides remove() to achieve this:

NoteActivity.java
OnItemClickListener noteClickListener = new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Note note = notesAdapter.getItem(position);
        notesBox.remove(note);
        Log.d(App.TAG, "Deleted note, ID: " + note.getId());
        ...
    }
};

NoteActivity.kt
private val noteClickListener = OnItemClickListener { _, _, position, _ ->
    notesAdapter.getItem(position)?.also {
        notesBox.remove(it)
        Log.d(App.TAG, "Deleted note, ID: " + it.id)
    }
    ...
}

...
onTap: () => _vm._box.remove(notes[index].id),
...

Querying notes

To query and display notes with a list adapter a Query instance is built once:

NoteActivity.java
@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    // Query all notes, sorted a-z by their text.
    notesQuery = notesBox.query().order(Note_.text).build();
    ...
}

NoteActivity.kt
public override fun onCreate(savedInstanceState: Bundle?) {
    ...
    // Query all notes, sorted a-z by their text.
    notesQuery = notesBox.query {
        order(Note_.text)
    }
    ...
}

class ViewModel {
  final Store _store;
  late final Box<Note> _box;
  late final Query<Note> _query;
  
  ViewModel(Directory dir)
      : _store = Store(getObjectBoxModel(), directory: dir.path + '/objectbox') {
    _box = _store.box<Note>();
    _query = _box.query().order(Note_.date, flags: Order.descending).build();
  }
  
  ...

And then executed each time any notes change:

NoteActivity.java
private void updateNotes() {
    List<Note> notes = notesQuery.find();
    notesAdapter.setNotes(notes);
}

NoteActivity.kt
private fun updateNotes() {
    val notes = notesQuery.find()
    notesAdapter.setNotes(notes)
}

List<Note> get allNotes => _query.find();

In addition to an order, you can add various conditions, like equality or less/greater than, when building a query.

Updating notes and more

What is not shown in the example, is how to update an existing (== the ID is not 0) note. Just modify any of its properties and call put() again with the changed object:

note.setText("This note has changed.");
notesBox.put(note);

note.text = "This note has changed."
notesBox.put(note)

note.text = "This note has changed.";
_box.put(note);

There are additional methods to put, find, query, count or remove entities. Check out the methods of the Box class in API docs (for Java/Kotlin or Dart) to learn more.

Setting up the database

Now that you saw ObjectBox in action, how did we get that BoxStore instance? Typically you should set up a BoxStore once for the whole app. This example uses a helper class as recommended in the Getting Started guide.

Remember: ObjectBox is a NoSQL database on its own and thus NOT based on SQL or SQLite. That’s why you do not need to set up “CREATE TABLE” statements during initialization.