akka.actor.DynamicAccess.scala Maven / Gradle / Ivy
/**
* Copyright (C) 2009-2014 Typesafe Inc.
*/
package akka.actor
import scala.collection.immutable
import java.lang.reflect.InvocationTargetException
import scala.reflect.ClassTag
import scala.util.Try
/**
* The DynamicAccess implementation is the class which is used for
* loading all configurable parts of an actor system (the
* [[akka.actor.ReflectiveDynamicAccess]] is the default implementation).
*
* This is an internal facility and users are not expected to encounter it
* unless they are extending Akka in ways which go beyond simple Extensions.
*/
abstract class DynamicAccess {
/**
* Convenience method which given a `Class[_]` object and a constructor description
* will create a new instance of that class.
*
* {{{
* val obj = DynamicAccess.createInstanceFor(clazz, Seq(classOf[Config] -> config, classOf[String] -> name))
* }}}
*/
def createInstanceFor[T: ClassTag](clazz: Class[_], args: immutable.Seq[(Class[_], AnyRef)]): Try[T]
/**
* Obtain a `Class[_]` object loaded with the right class loader (i.e. the one
* returned by `classLoader`).
*/
def getClassFor[T: ClassTag](fqcn: String): Try[Class[_ <: T]]
/**
* Obtain an object conforming to the type T, which is expected to be
* instantiated from a class designated by the fully-qualified class name
* given, where the constructor is selected and invoked according to the
* `args` argument. The exact usage of args depends on which type is requested,
* see the relevant requesting code for details.
*/
def createInstanceFor[T: ClassTag](fqcn: String, args: immutable.Seq[(Class[_], AnyRef)]): Try[T]
/**
* Obtain the Scala “object” instance for the given fully-qualified class name, if there is one.
*/
def getObjectFor[T: ClassTag](fqcn: String): Try[T]
/**
* This is the class loader to be used in those special cases where the
* other factory method are not applicable (e.g. when constructing a ClassLoaderBinaryInputStream).
*/
def classLoader: ClassLoader
}
/**
* 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.
*/
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 + " 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 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 }
}
}
}