如何使用不可变项和Egg模式设置基类字段

Question

我正在使用Java的https://immutables.github.io/，并且在使用基类和设置其字段一次时遇到麻烦。

我有不可变对象，它们利用Egg模式共享字段，例如：

interface HousingBase {
  int streetNumber();
  String streetName();
  int zip();
}

@Value.Immutable
interface House extends HousingBase {
  long lotSize();
}

@Value.Immutable
interface Apartment extends HousingBase {
  int apartmentNumber();
}

问题是我的代码从一组HousingBase字段构造这些对象，而我最终得到重复的代码，例如：

public ImmutableHouse toHouse(HouseLocation location) {
  return ImmutableHouse.builder()
    .setStreetNumber(location.number())
    .setStreetName(location.street())
    .setZip(location.zip())
    .setLotSize(location.size())
    .build();
}
public ImmutableApartment toHouse(ApartmentLocation location) {
  return ImmutableApartment.builder()
    .setStreetNumber(location.number())
    .setStreetName(location.street())
    .setZip(location.zip())
    .setApartmentNumber(location.complex())
    .build();
}

我真正想要的是某种方法来设置HousingBase字段，以便对它们进行一次定义。像这样：

public ImmutableApartment toHouse(ApartmentLocation location) {
  return setBaseFields(ImmutableApartment.builder(), location)
    .setApartmentNumber(location.complex())
    .build();
}

private Builder setBaseFields(Builder builder, Location location) {
  return builder
    .setStreetNumber(location.number())
    .setStreetName(location.street())
    .setZip(location.zip())
} 

但是我不知道如何使它正常工作，或者在此库中是否可行。

Answer 1

泛型！

private static <B extends Builder> B setBaseFields(B builder, Location location) {