[英]How to get a list of objects from Guice by their classes?
我定義了一些“變壓器”(功能),並需要它們的列表。 它們每個都是由Guice創建的,我正在使用以下代碼來獲取列表:
public class CombinedTransformer extends AbstractTransformer {
@Inject CombinedTransformer(
FirstTransformer firstTransformer,
SecondTransformer secondTransformer,
ThirdTransformer thirdTransformer) {
transformers = ImmutableList.of(
firstTransformer,
secondTransformer,
thirdTransformer);
我的名單很長,所以我想知道是否有更簡單的方法,例如
public class CombinedTransformer extends AbstractTransformer {
@Inject CombinedTransformer(Injector injector) {
transformers = injector.getList(
FirstTransformer.class,
SecondTransformer.class,
ThirdTransformer.class);
}
}
有這樣的東西嗎?
您可以為此使用多重綁定 :
Multibinder<AbstractTransformer> multibinder = Multibinder.newSetBinder(binder(), AbstractTransformer.class);
multibinder.addBinding().to(FirstTransformer.class);
multibinder.addBinding().to(SecondTransformer.class);
multibinder.addBinding().to(ThirdsTransformer.class);
然后可以注入Set<AbstractTransformer>
:
@Inject
CombinedTransformer(Set<AbstractTransformer> transformers) {
// do whatever you want with the set
}
但是,如果不直接使用多重綁定,就無法做到這一點。 如果確實需要使用靜態已知的類列表來獲取對象列表,則可以在注入器周圍編寫包裝器並使用它:
public class ListInjectorWrapper {
private final Injector injector;
@Inject
ListInjectorWrapper(Injector injector) {
this.injector = injector;
}
@SafeVarargs
public final <T> List<T> getList(Class<? extends T>... classes) {
return Arrays.stream(classes).map(clazz -> injector.getInstance(clazz))
.collect(Collectors.toList());
}
}
然后注入它並用它來獲得您的變壓器:
@Inject
CombinedTransformer(ListInjectorWrapper injectorWrapper) {
transformers = injectorWrapper.getList(
FirstTransformer.class,
SecondTransformer.class,
ThirdTransformer.class
);
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.