hvanhovell commented on code in PR #42069: URL: https://github.com/apache/spark/pull/42069#discussion_r1278181125
########## core/src/main/scala/org/apache/spark/util/StubClassLoader.scala: ########## @@ -0,0 +1,79 @@ +/* + * 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 org.apache.xbean.asm9.{ClassWriter, Opcodes} + +/** + * [[ClassLoader]] that replaces missing classes with stubs, if the cannot be found. It will only + * do this for classes that are marked for stubbing. + * + * While this is generally not a good idea. In this particular case this is used to load lambda's + * whose capturing class contains unknown (and unneeded) classes. The lambda itself does not need + * the class and therefor is safe to replace by a stub. + */ +class StubClassLoader(parent: ClassLoader, shouldStub: String => Boolean) + extends ClassLoader(parent) { + override def findClass(name: String): Class[_] = { + if (!shouldStub(name)) { + throw new ClassNotFoundException(name) + } + val bytes = StubClassLoader.generateStub(name) + defineClass(name, bytes, 0, bytes.length) + } +} + +object StubClassLoader { + def apply(parent: ClassLoader, binaryName: Seq[String]): StubClassLoader = { + new StubClassLoader(parent, name => binaryName.exists(p => name.startsWith(p))) + } + + def generateStub(binaryName: String): Array[Byte] = { + // Convert binary names to internal names. + val name = binaryName.replace('.', '/') + val classWriter = new ClassWriter(0) + classWriter.visit( + 49, + Opcodes.ACC_PUBLIC + Opcodes.ACC_SUPER, + name, + null, + "java/lang/Object", + null) + classWriter.visitSource(name + ".java", null) + + // Generate constructor. + val ctorWriter = classWriter.visitMethod( Review Comment: Can you file a follow-up to make this throw an exception? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
