在Guice注入一个通用工厂 [英] Injecting a generic factory in Guice
问题描述
以下代码是给出一个 Foo< T>
Bar< T> 。工厂不在乎什么 T
是:对于任何类型 T
,它可以使一个 Foo< T>
中的< T> 。
The following code is an example of a factory that produces a Bar<T>
given a Foo<T>
. The factory doesn't care what T
is: for any type T
, it can make a Bar<T>
from a Foo<T>
.
import com.google.inject.*;
import com.google.inject.assistedinject.*;
class Foo<T> {
public void flip(T x) { System.out.println("flip: " + x); }
}
interface Bar<T> {
void flipflop(T x);
}
class BarImpl<T> implements Bar<T> {
Foo<T> foo;
@Inject
BarImpl(Foo<T> foo) { this.foo = foo; }
public void flipflop(T x) { foo.flip(x); System.out.println("flop: " + x); }
}
interface BarFactory {
<T> Bar<T> create(Foo<T> f);
}
class Module extends AbstractModule {
public void configure() {
bind(BarFactory.class)
.toProvider(
FactoryProvider.newFactory( BarFactory.class, BarImpl.class )
);
}
}
public class GenericInject {
public static void main(String[] args) {
Injector injector = Guice.createInjector(new Module());
Foo<Integer> foo = new Foo<Integer>();
Bar<Integer> bar = injector.getInstance(BarFactory.class).create(foo);
bar.flipflop(0);
}
}
当我运行代码时,我收到以下错误从Guice:
When I run the code, I get the following errors from Guice:
1) No implementation for BarFactory was bound.
at Module.configure(GenericInject.java:38)
2) Bar<T> cannot be used as a key; It is not fully specified.
我们可以在Guice文档中找到泛型的唯一参考资料,说使用 TypeLiteral
。但是我没有字面类型,我有一个与工厂无关的通用占位符。任何提示?
The only reference I can find to generics in the Guice documentation says to use a TypeLiteral
. But I don't have a literal type, I have a generic placeholder that isn't relevant to the factory at all. Any tips?
推荐答案
一个选项是手写BarFactory样板:
One option is to just write the BarFactory boilerplate by hand:
class BarImplFactory implements BarFactory {
public <T> Bar<T> create(Foo<T> f) {
return new BarImpl(f);
}
}
绑定成为
bind(BarFactory.class).to(BarImplFactory.class);
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