Guice MapBinder

Question

我在Java + Kotlin项目中使用Guice将算法实现的映射注入到特定的bean中，但我不断得到

1) No implementation for java.util.Map<java.lang.String, ? extends com.scherule.scheduling.algorithms.SchedulingAlgorithm> annotated with @com.google.inject.name.Named(value=scheduling.algorithms) was bound.
  while locating java.util.Map<java.lang.String, ? extends com.scherule.scheduling.algorithms.SchedulingAlgorithm> annotated with @com.google.inject.name.Named(value=scheduling.algorithms)
    for the 2nd parameter of com.scherule.scheduling.SchedulingJobConsumer.<init>(SchedulingJobConsumer.kt:17)
  while locating com.scherule.scheduling.SchedulingJobConsumer

模块的定义如下所示：

class AlgorithmsModule : AbstractModule() {

    override fun configure() {
        MapBinder.newMapBinder(binder(),
                String::class.java,
                SchedulingAlgorithm::class.java,
                Names.named("scheduling.algorithms")
        ).addBinding("interval-projection").toInstance(IntervalProjectionAlgorithm())
    }

}

调用者代码是：

@Singleton
class SchedulingJobConsumer
@Inject constructor(
        @Named("scheduling.channel") channel: Channel,
        @Named("scheduling.algorithms") val schedulers: Map<String, SchedulingAlgorithm>
) : DefaultConsumer(channel) ...

但当我这么做的时候

injector.getInstance(Key.get(new TypeLiteral<Map<String, SchedulingAlgorithm>>() {}, named("scheduling.algorithms")))

它就在那里。怎么了？

Answer 1

问题在于Kotlin Generics != Java Generics这一事实。

这个Kotlin代码。

 @Named("scheduling.algorithms") val schedulers: Map<String, SchedulingAlgorithm>

获取编译为

Map<String, ? extends SchedulingAlgorithm> and not Map<String, SchedulingAlgorithm>

当注入Guice时，它正在寻找没有绑定的Map<String, ? extends SchedulingAlgorithm>，因为MapBinder为Map<String, SchedulingAlgorithm>创建了绑定。

Answer 2

您可以尝试在AlgorithmsModule中添加以下成员方法，而不是使用MapBinder

@Provides
@Singleton
@Named("scheduling.algorithms")
fun schedulingAlgorithms(): Map<String, @JvmSuppressWildcards SchedulingAlgorithm> {
    return IntervalProjectionAlgorithm()
}