Composition Over Inheritance For Realmobjects With Gson Serialization

I'm considering Realm as a database solution for various reasons, but the big one currently being the TransactionTooLargeException now being thrown in Nougat has made it so I have

Solution 1:

You should create a new RealmObject class for each flattened concrete class, and map your JSON representation to them.

To retain inheritance, you can simulate it by inheriting getters/setters from interfaces that inherit from one another.

publicinterfaceIAnimalextendsRealmModel {    
    intgetNumberOfLegs();
    voidsetNumberOfLegs(int legs);
    booleangetHasFur();
    voidsetHasFur(boolean hasFur);
}

publicinterfaceIDogextendsIAnimal {
    String getColor();
    voidsetColor(String color);
    booleangetCanDoTricks();
    voidsetCanDoTricks();
}

publicinterfaceIGermanShepherdextendsIDog {
    booleangetIsGuardDog();
    voidsetIsGuardDog(boolean isGuardDog);
    booleangetIsAtRiskOfHipDysplasia();
    voidsetIsAtRiskOfHipDysplasia(boolean isAtRisk);
}

Because then you can do

publicclassGermanShepardextendsRealmObjectimplementsIGermanShepard{
      privateint numLegs;
      privateboolean hasFur;
      privateString color;
      privateboolean canDoTricks;
      privateboolean isGuardDog;
      privateboolean isAtRiskofHipDysplasia;

      // inherited getters/setters
}

You can even make repository class out of it

publicabstractclassAnimalRepository<TextendsIAnimal> {
     protected Class<T> clazz;

     publicAnimalRepository(Class<T> clazz) {
         this.clazz = clazz;
     }

     public RealmResults<T> findAll(Realm realm) {
         return realm.where(clazz).findAll();
     }
}

 @Singleton
 publicclassGermanShepardRepositoryextendsAnimalRepository<GermanShepard> {
      @Inject
      publicGermanShepardRepository() {
          super(GermanShepard.class);
      }
 }

And then

@InjectGermanShepardRepository germanShepardRepository;

RealmResults<GermanShepard> results = germanShepardRepository.findAll(realm);

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But you can indeed merge them into one class and then give it a String type; parameter to know what type it originally was. That's probably even better than having all these GermanShepards.