How to persist object to room database in Android. How to persist list to room database in Android.

YourTypeConverterForPersistList.java

//Saving List.
//If you want persist List you need implement TypeConverter
//List<User> to json as string; json as string to List<User>.
public class YourTypeConverterForPersistList {
    
    @TypeConverter
    public String listUsersToJson(List<User> users) {
        Gson gson = new Gson();
        Type type = new TypeToken<List<User>>() {}.getType();
        String json = gson.toJson(users, type);
        return json;
    }

    @TypeConverter
    public List<User> jsonToListUsers(String jsonListUsersAsString) {
        Gson gson = new Gson();
        Type type = new TypeToken<List<User>>() {}.getType();
        List<User> users = gson.fromJson(jsonListUsersAsString, type);
        return users;
    }

}

YourTypeConverterForPersistObject.java

//Saving object.
//If you want persist some Object you need implement TypeConverter
//Note: User to json as string; json as string to User.
public class YourTypeConverterForPersistObject {

    @TypeConverter
    public String userToJson(User user) {
        return new Gson().toJson(user);
    }
    
    @TypeConverter
    public User jsonToUser(String jsonUserAsString) {
        return new Gson().fromJson(jsonAsString, User.class);
    }

}