akka.actor.ReflectiveDynamicAccess.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2009-2020 Lightbend Inc.
*/
package akka.actor
import java.lang.reflect.InvocationTargetException
import scala.collection.immutable
import scala.reflect.ClassTag
import scala.util.Failure
import scala.util.Try
import akka.annotation.DoNotInherit
/**
* This is the default [[akka.actor.DynamicAccess]] implementation used by [[akka.actor.ExtendedActorSystem]]
* unless overridden. It uses reflection to turn fully-qualified class names into `Class[_]` objects
* and creates instances from there using `getDeclaredConstructor()` and invoking that. The class loader
* to be used for all this is determined by the actor system’s class loader by default.
*
* Not for user extension or construction
*/
@DoNotInherit
class ReflectiveDynamicAccess(val classLoader: ClassLoader) extends DynamicAccess {
override def getClassFor[T: ClassTag](fqcn: String): Try[Class[_ <: T]] =
Try[Class[_ <: T]]({
val c = Class.forName(fqcn, false, classLoader).asInstanceOf[Class[_ <: T]]
val t = implicitly[ClassTag[T]].runtimeClass
if (t.isAssignableFrom(c)) c else throw new ClassCastException(t.toString + " is not assignable from " + c)
})
override def createInstanceFor[T: ClassTag](clazz: Class[_], args: immutable.Seq[(Class[_], AnyRef)]): Try[T] =
Try {
val types = args.map(_._1).toArray
val values = args.map(_._2).toArray
val constructor = clazz.getDeclaredConstructor(types: _*)
constructor.setAccessible(true)
val obj = constructor.newInstance(values: _*)
val t = implicitly[ClassTag[T]].runtimeClass
if (t.isInstance(obj)) obj.asInstanceOf[T]
else throw new ClassCastException(clazz.getName + " is not a subtype of " + t)
}.recover { case i: InvocationTargetException if i.getTargetException ne null => throw i.getTargetException }
override def createInstanceFor[T: ClassTag](fqcn: String, args: immutable.Seq[(Class[_], AnyRef)]): Try[T] =
getClassFor(fqcn).flatMap { c =>
createInstanceFor(c, args)
}
override def classIsOnClasspath(fqcn: String): Boolean =
getClassFor(fqcn) match {
case Failure(_: ClassNotFoundException | _: NoClassDefFoundError) =>
false
case _ =>
true
}
override def getObjectFor[T: ClassTag](fqcn: String): Try[T] = {
val classTry =
if (fqcn.endsWith("$")) getClassFor(fqcn)
else getClassFor(fqcn + "$").recoverWith { case _ => getClassFor(fqcn) }
classTry.flatMap { c =>
Try {
val module = c.getDeclaredField("MODULE$")
module.setAccessible(true)
val t = implicitly[ClassTag[T]].runtimeClass
module.get(null) match {
case null => throw new NullPointerException
case x if !t.isInstance(x) => throw new ClassCastException(fqcn + " is not a subtype of " + t)
case x: T => x
}
}.recover { case i: InvocationTargetException if i.getTargetException ne null => throw i.getTargetException }
}
}
}