Java tutorial
/** * 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.cassandra.continuations; import java.lang.annotation.Annotation; import java.lang.instrument.ClassFileTransformer; import java.lang.instrument.IllegalClassFormatException; import java.security.ProtectionDomain; import java.util.List; import java.util.Set; import java.util.HashSet; import java.util.StringTokenizer; import org.objectweb.asm.ClassReader; import org.objectweb.asm.tree.AnnotationNode; import org.objectweb.asm.tree.ClassNode; import org.objectweb.asm.tree.MethodNode; import org.apache.commons.javaflow.bytecode.transformation.ResourceTransformer; import org.apache.commons.javaflow.bytecode.transformation.bcel.BcelClassTransformer; /** * Author : Avinash Lakshman ( alakshman@facebook.com) & Prashant Malik ( pmalik@facebook.com ) */ class ContinuationClassTransformer implements ClassFileTransformer { private static final String targetAnnotation_ = "Suspendable"; private ResourceTransformer transformer_; public ContinuationClassTransformer(String agentArguments, ResourceTransformer transformer) { super(); transformer_ = transformer; } public byte[] transform(ClassLoader classLoader, String className, Class redefiningClass, ProtectionDomain domain, byte[] bytes) throws IllegalClassFormatException { /* * Use the ASM class reader to see which classes support * the Suspendable annotation. If they do then those * classes need to have their bytecodes transformed for * Continuation support. */ ClassReader classReader = new ClassReader(bytes); ClassNode classNode = new ClassNode(); classReader.accept(classNode, true); List<AnnotationNode> annotationNodes = classNode.visibleAnnotations; for (AnnotationNode annotationNode : annotationNodes) { if (annotationNode.desc.contains(ContinuationClassTransformer.targetAnnotation_)) { bytes = transformer_.transform(bytes); } } return bytes; } }