RealmListConverter.java

public class RealmListConverter<T extends RealmObject> implements
        TypeConverter<RealmList<T>> {

    @FunctionalInterface
    public interface SingleFieldSerialization<T> {
        Object getValue(T object);
    }

    Class<T> clazz;
    TypeConverter<T> typeConverter;
    JsonMapper<T> mapper;
    public final String mLogTag = getClass().getSimpleName();

    private SingleFieldSerialization<T> singleFieldSerialization;


    public void setSingleFieldSerialization(SingleFieldSerialization<T>
                                                    singleFieldSerialization) {
        this.singleFieldSerialization = singleFieldSerialization;
    }

    protected void init() {
        if (typeConverter == null && mapper == null) {
            try {
                typeConverter = LoganSquare.typeConverterFor(getPersistentClass());
            } catch (NoSuchTypeConverterException e) {
                Log.w(mLogTag, "TypeConverter failed. Using mapper instead");
                mapper = LoganSquare.mapperFor(getPersistentClass());
            }
        }
    }


    @SuppressWarnings("unchecked")
    public Class<T> getPersistentClass() {
        if (clazz == null) {
            this.clazz = (Class<T>) ((ParameterizedType) getClass()
                    .getGenericSuperclass()).getActualTypeArguments()[0];
        }
        return clazz;
    }


    @Override
    public RealmList<T> parse(JsonParser jsonParser) throws IOException {
        init();
        RealmList<T> list = new RealmList<>();
        if (jsonParser.getCurrentToken() == JsonToken.START_ARRAY) {
            while (jsonParser.nextToken() != JsonToken.END_ARRAY) {
                T object = typeConverter != null ? typeConverter.parse
                        (jsonParser) : mapper.parse(jsonParser);
                if (object != null) {
                    list.add(object);
                }
            }
        }
        return list;
    }

    @Override
    public void serialize(RealmList<T> list, String fieldName, boolean
            writeFieldNameForObject, JsonGenerator jsonGenerator) throws
            IOException {
        if (writeFieldNameForObject) {
            if (list == null || list.isEmpty()) {
                return;
            }
            jsonGenerator.writeFieldName(fieldName);
        }
        if (list == null || list.isEmpty()) {
            jsonGenerator.writeNull();
            return;
        }
        jsonGenerator.writeStartArray();
        if (singleFieldSerialization != null) {
            secondConditionSerialization(list, jsonGenerator);
        } else {
            init();
            for (T object : list) {
                serializingTypeConverterMapper(object, fieldName,
                        jsonGenerator);
            }
        }
        jsonGenerator.writeEndArray();
    }

    public void secondConditionSerialization(RealmList<T> list, JsonGenerator
            jsonGenerator) {
        try {
            JsonMapper<Object> objectMapper = LoganSquare.mapperFor(Object
                    .class);
            for (T object : list) {
                if (object != null) {
                    objectMapper.serialize(singleFieldSerialization.getValue
                            (object), jsonGenerator, true);
                } else {
                    jsonGenerator.writeNull();
                }
            }
        } catch (IOException e) {
            Log.w(mLogTag, Log.getStackTraceString(e));
        }

    }

    private void serializingTypeConverterMapper(T object, String fieldName,
                                                JsonGenerator jsonGenerator) {
        try {
            if (object != null) {
                if (typeConverter != null) {
                    typeConverter.serialize(object, fieldName, false,
                            jsonGenerator);
                } else {
                    mapper.serialize(object, jsonGenerator, true);
                }
            } else {
                jsonGenerator.writeNull();
            }
        } catch (IOException e) {
            Log.w(mLogTag, Log.getStackTraceString(e));
        }
    }

RealmListSampleConverter.java

public class RealmListCategoryItemConverter extends RealmListConverter<Sample> {
//Assume that Sample is an extension of RealmObject
}