class JsonMapAttributeConverter implements AttributeConverter<Map<String, String>, String> {

    @Override
    public String convertToDatabaseColumn(Map<String, String> attribute) {
        return JsonUtil.toJson(attribute);
    }

    @Override
    public Map<String, String> convertToEntityAttribute(String dbData) {<FILL_FUNCTION_BODY>}
}

        TypeReference<Map<String, String>> typeReference = new TypeReference<>() {};
        return JsonUtil.fromJson(dbData, typeReference);
    
<no_super_class>