从protobuf描述符获取默认实例

您可以通过 DynamicMessage 班

Message PhoneBook {
    repeated Person people = 1;
}
Message Person {
    required Name name = 1;
    optional String phone = 2;
}
Message Name {
    required String family_name = 1;
    required String given_name = 2;
}

获取的默认实例的代码 People

PhoneBook phoneBook = phoneBook.getDefaultInstance();
Descriptors.Descriptor personDescriptor = phoneBook.getDescriptor().findNestedTypeByName("people");
DynamicMessage defaultPeopleInstance = DynamicMessage.newBuilder(personDescriptor).getDefaultInstanceForType().build();
assert defaultPeopleInstance == People.getDefaultInstance();