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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.util
import java.net.{URLClassLoader, URL}
import java.util.Enumeration
import java.util.concurrent.ConcurrentHashMap
import scala.collection.JavaConversions._
/**
* URL class loader that exposes the `addURL` and `getURLs` methods in URLClassLoader.
*/
private[spark] class MutableURLClassLoader(urls: Array[URL], parent: ClassLoader)
extends URLClassLoader(urls, parent) {
override def addURL(url: URL): Unit = {
super.addURL(url)
}
override def getURLs(): Array[URL] = {
super.getURLs()
}
}
/**
* A mutable class loader that gives preference to its own URLs over the parent class loader
* when loading classes and resources.
*/
private[spark] class ChildFirstURLClassLoader(urls: Array[URL], parent: ClassLoader)
extends MutableURLClassLoader(urls, null) {
private val parentClassLoader = new ParentClassLoader(parent)
/**
* Used to implement fine-grained class loading locks similar to what is done by Java 7. This
* prevents deadlock issues when using non-hierarchical class loaders.
*
* Note that due to some issues with implementing class loaders in
* Scala, Java 7's `ClassLoader.registerAsParallelCapable` method is not called.
*/
private val locks = new ConcurrentHashMap[String, Object]()
override def loadClass(name: String, resolve: Boolean): Class[_] = {
var lock = locks.get(name)
if (lock == null) {
val newLock = new Object()
lock = locks.putIfAbsent(name, newLock)
if (lock == null) {
lock = newLock
}
}
lock.synchronized {
try {
super.loadClass(name, resolve)
} catch {
case e: ClassNotFoundException =>
parentClassLoader.loadClass(name, resolve)
}
}
}
override def getResource(name: String): URL = {
val url = super.findResource(name)
val res = if (url != null) url else parentClassLoader.getResource(name)
res
}
override def getResources(name: String): Enumeration[URL] = {
val urls = super.findResources(name)
val res =
if (urls != null && urls.hasMoreElements()) {
urls
} else {
parentClassLoader.getResources(name)
}
res
}
override def addURL(url: URL) {
super.addURL(url)
}
}
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