[英]How to get a list of objects from Guice by their classes?
I defined some "transformers" (functions) and need a list of them. 我定义了一些“变压器”(功能),并需要它们的列表。 Each of them gets created by Guice and I'm using this code to get the list: 它们每个都是由Guice创建的,我正在使用以下代码来获取列表:
public class CombinedTransformer extends AbstractTransformer {
@Inject CombinedTransformer(
FirstTransformer firstTransformer,
SecondTransformer secondTransformer,
ThirdTransformer thirdTransformer) {
transformers = ImmutableList.of(
firstTransformer,
secondTransformer,
thirdTransformer);
My list is pretty long, so I wonder if there's a simpler way, something like 我的名单很长,所以我想知道是否有更简单的方法,例如
public class CombinedTransformer extends AbstractTransformer {
@Inject CombinedTransformer(Injector injector) {
transformers = injector.getList(
FirstTransformer.class,
SecondTransformer.class,
ThirdTransformer.class);
}
}
Is there something like this? 有这样的东西吗?
You can use multibindings for this: 您可以为此使用多重绑定 :
Multibinder<AbstractTransformer> multibinder = Multibinder.newSetBinder(binder(), AbstractTransformer.class);
multibinder.addBinding().to(FirstTransformer.class);
multibinder.addBinding().to(SecondTransformer.class);
multibinder.addBinding().to(ThirdsTransformer.class);
Then you can inject Set<AbstractTransformer>
: 然后可以注入Set<AbstractTransformer>
:
@Inject
CombinedTransformer(Set<AbstractTransformer> transformers) {
// do whatever you want with the set
}
But you can't do it without using multibindings directly. 但是,如果不直接使用多重绑定,就无法做到这一点。 If you really need to get a list of objects using statically known list of classes, you can write a wrapper around an injector and use it: 如果确实需要使用静态已知的类列表来获取对象列表,则可以在注入器周围编写包装器并使用它:
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());
}
}
Then inject it and use it to get your transformers: 然后注入它并用它来获得您的变压器:
@Inject
CombinedTransformer(ListInjectorWrapper injectorWrapper) {
transformers = injectorWrapper.getList(
FirstTransformer.class,
SecondTransformer.class,
ThirdTransformer.class
);
}
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