我如何编写一个通用的Guice绑定函数？ [英] How can I write a generic Guice binding function?

问题描述

如何在下面的Guice绑定代码中抽象出Option类型，用 Option ？

How can I abstract the Option type in the below Guice binding code, substituting a generic parameter for Option?

ArrayList<Class<? extends Option>> options = 
 new ArrayList<Class<? extends Option>>();
bindMultibinder(annotation, options);

public Key<Set<Option>> bindMultibinder(
 Named annotation, ArrayList<Class<? extends Option>> contents) {
   Multibinder<Option> options = 
    Multibinder.newSetBinder(binder(), Option.class, annotation);
   for (Class<? extends Option> option : contents) {
      options.addBinding().to(option);
   }
   final Key<Set<Option>> multibinderKey = 
    Key.get(new TypeLiteral<Set<Option>>(){}, annotation);
   return multibinderKey;
}

推荐答案

感谢 Stuart McCulloch 回答：

Thanks to Stuart McCulloch on Google Groups for answering:

新的TypeLiteral< ...>（）{}匿名类技巧仅在
类型参数在编译时已知的情况下才有效

^ the new TypeLiteral<...>(){} anonymous class trick only works when the type parameter is known at compile time.

如果您需要在运行时构建泛型类型，则可以使用
com.google.inject.util.Types实用程序类，例如：

If you need to build generic types at runtime you can use the com.google.inject.util.Types utility class, for example:

final Key<Set<T>> multibinderKey =
    Key.get( Types.setOf( superClass ), annotation );

为了正确地构建它，我修改了它，如下所示：

To get this to build correctly, I modified it as follows:

final Key<?> multibinderKey = Key.get(Types.setOf( superClass ), annotation);

所以完整的泛型方法是：

So the complete generic method is:

public <T> Key<?> bindMultibinder(
 Named annotation, Class<T> superClass, ArrayList<Class<? extends T>> contents) {
   Multibinder<T> options = 
    Multibinder.newSetBinder(binder(), superClass, annotation);
   for (Class<? extends T> t : contents) {
      options.addBinding().to(t);
   }
   final Key<?> multibinderKey = Key.get(Types.setOf( superClass ), annotation);
   return multibinderKey;
}

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