Thread-local Realm

RealmManager.java

@Singleton
public class RealmManager {
    private ThreadLocal<Realm> realms;

    @Inject
    public RealmManager() {
        realms = new ThreadLocal<>();
    }

    public Realm openRealm() {
        Realm realm = realms.get();
        if(realm != null && !realm.isClosed()) {
            throw new IllegalStateException("Realm is already open");
        }
        realm = Realm.getDefaultInstance();
        realms.set(realm);
        return realm;
    }

    public Realm getRealm() {
        Realm realm = realms.get();
        if(realm == null) {
            throw new IllegalStateException("There is no open Realm on this thread");
        }
        return realm;
    }

    public void closeRealm() {
        Realm realm = realms.get();
        if(realm == null) {
            throw new IllegalStateException("No Realm found to close");
        }
        if(!realm.isClosed()) {
            realm.close();
        }
        realms.set(null);
    }
}