001/* 002 * Copyright 2002-2007 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.instrument.classloading; 018 019import java.lang.instrument.ClassFileTransformer; 020import java.lang.instrument.IllegalClassFormatException; 021import java.security.ProtectionDomain; 022import java.util.ArrayList; 023import java.util.List; 024 025/** 026 * ClassFileTransformer-based weaver, allowing for a list of transformers to be 027 * applied on a class byte array. Normally used inside class loaders. 028 * 029 * <p>Note: This class is deliberately implemented for minimal external dependencies, 030 * since it is included in weaver jars (to be deployed into application servers). 031 * 032 * @author Rod Johnson 033 * @author Costin Leau 034 * @author Juergen Hoeller 035 * @since 2.0 036 */ 037public class WeavingTransformer { 038 039 private final ClassLoader classLoader; 040 041 private final List<ClassFileTransformer> transformers = new ArrayList<ClassFileTransformer>(); 042 043 044 /** 045 * Create a new WeavingTransformer for the given class loader. 046 * @param classLoader the ClassLoader to build a transformer for 047 */ 048 public WeavingTransformer(ClassLoader classLoader) { 049 if (classLoader == null) { 050 throw new IllegalArgumentException("ClassLoader must not be null"); 051 } 052 this.classLoader = classLoader; 053 } 054 055 056 /** 057 * Add a class file transformer to be applied by this weaver. 058 * @param transformer the class file transformer to register 059 */ 060 public void addTransformer(ClassFileTransformer transformer) { 061 if (transformer == null) { 062 throw new IllegalArgumentException("Transformer must not be null"); 063 } 064 this.transformers.add(transformer); 065 } 066 067 068 /** 069 * Apply transformation on a given class byte definition. 070 * The method will always return a non-null byte array (if no transformation has taken place 071 * the array content will be identical to the original one). 072 * @param className the full qualified name of the class in dot format (i.e. some.package.SomeClass) 073 * @param bytes class byte definition 074 * @return (possibly transformed) class byte definition 075 */ 076 public byte[] transformIfNecessary(String className, byte[] bytes) { 077 String internalName = className.replace(".", "/"); 078 return transformIfNecessary(className, internalName, bytes, null); 079 } 080 081 /** 082 * Apply transformation on a given class byte definition. 083 * The method will always return a non-null byte array (if no transformation has taken place 084 * the array content will be identical to the original one). 085 * @param className the full qualified name of the class in dot format (i.e. some.package.SomeClass) 086 * @param internalName class name internal name in / format (i.e. some/package/SomeClass) 087 * @param bytes class byte definition 088 * @param pd protection domain to be used (can be null) 089 * @return (possibly transformed) class byte definition 090 */ 091 public byte[] transformIfNecessary(String className, String internalName, byte[] bytes, ProtectionDomain pd) { 092 byte[] result = bytes; 093 for (ClassFileTransformer cft : this.transformers) { 094 try { 095 byte[] transformed = cft.transform(this.classLoader, internalName, null, pd, result); 096 if (transformed != null) { 097 result = transformed; 098 } 099 } 100 catch (IllegalClassFormatException ex) { 101 throw new IllegalStateException("Class file transformation failed", ex); 102 } 103 } 104 return result; 105 } 106 107}