001/* 002 * Copyright 2002-2019 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.io.IOException; 020import java.io.InputStream; 021import java.lang.instrument.ClassFileTransformer; 022import java.lang.instrument.IllegalClassFormatException; 023import java.net.URL; 024import java.util.Enumeration; 025import java.util.HashMap; 026import java.util.LinkedList; 027import java.util.List; 028import java.util.Map; 029 030import org.springframework.core.DecoratingClassLoader; 031import org.springframework.lang.Nullable; 032import org.springframework.util.Assert; 033import org.springframework.util.FileCopyUtils; 034import org.springframework.util.StringUtils; 035 036/** 037 * ClassLoader decorator that shadows an enclosing ClassLoader, 038 * applying registered transformers to all affected classes. 039 * 040 * @author Rob Harrop 041 * @author Juergen Hoeller 042 * @author Costin Leau 043 * @since 2.0 044 * @see #addTransformer 045 * @see org.springframework.core.OverridingClassLoader 046 */ 047public class ShadowingClassLoader extends DecoratingClassLoader { 048 049 /** Packages that are excluded by default. */ 050 public static final String[] DEFAULT_EXCLUDED_PACKAGES = 051 new String[] {"java.", "javax.", "jdk.", "sun.", "oracle.", "com.sun.", "com.ibm.", "COM.ibm.", 052 "org.w3c.", "org.xml.", "org.dom4j.", "org.eclipse", "org.aspectj.", "net.sf.cglib", 053 "org.springframework.cglib", "org.apache.xerces.", "org.apache.commons.logging."}; 054 055 056 private final ClassLoader enclosingClassLoader; 057 058 private final List<ClassFileTransformer> classFileTransformers = new LinkedList<>(); 059 060 private final Map<String, Class<?>> classCache = new HashMap<>(); 061 062 063 /** 064 * Create a new ShadowingClassLoader, decorating the given ClassLoader, 065 * applying {@link #DEFAULT_EXCLUDED_PACKAGES}. 066 * @param enclosingClassLoader the ClassLoader to decorate 067 * @see #ShadowingClassLoader(ClassLoader, boolean) 068 */ 069 public ShadowingClassLoader(ClassLoader enclosingClassLoader) { 070 this(enclosingClassLoader, true); 071 } 072 073 /** 074 * Create a new ShadowingClassLoader, decorating the given ClassLoader. 075 * @param enclosingClassLoader the ClassLoader to decorate 076 * @param defaultExcludes whether to apply {@link #DEFAULT_EXCLUDED_PACKAGES} 077 * @since 4.3.8 078 */ 079 public ShadowingClassLoader(ClassLoader enclosingClassLoader, boolean defaultExcludes) { 080 Assert.notNull(enclosingClassLoader, "Enclosing ClassLoader must not be null"); 081 this.enclosingClassLoader = enclosingClassLoader; 082 if (defaultExcludes) { 083 for (String excludedPackage : DEFAULT_EXCLUDED_PACKAGES) { 084 excludePackage(excludedPackage); 085 } 086 } 087 } 088 089 090 /** 091 * Add the given ClassFileTransformer to the list of transformers that this 092 * ClassLoader will apply. 093 * @param transformer the ClassFileTransformer 094 */ 095 public void addTransformer(ClassFileTransformer transformer) { 096 Assert.notNull(transformer, "Transformer must not be null"); 097 this.classFileTransformers.add(transformer); 098 } 099 100 /** 101 * Copy all ClassFileTransformers from the given ClassLoader to the list of 102 * transformers that this ClassLoader will apply. 103 * @param other the ClassLoader to copy from 104 */ 105 public void copyTransformers(ShadowingClassLoader other) { 106 Assert.notNull(other, "Other ClassLoader must not be null"); 107 this.classFileTransformers.addAll(other.classFileTransformers); 108 } 109 110 111 @Override 112 public Class<?> loadClass(String name) throws ClassNotFoundException { 113 if (shouldShadow(name)) { 114 Class<?> cls = this.classCache.get(name); 115 if (cls != null) { 116 return cls; 117 } 118 return doLoadClass(name); 119 } 120 else { 121 return this.enclosingClassLoader.loadClass(name); 122 } 123 } 124 125 /** 126 * Determine whether the given class should be excluded from shadowing. 127 * @param className the name of the class 128 * @return whether the specified class should be shadowed 129 */ 130 private boolean shouldShadow(String className) { 131 return (!className.equals(getClass().getName()) && !className.endsWith("ShadowingClassLoader") && 132 isEligibleForShadowing(className)); 133 } 134 135 /** 136 * Determine whether the specified class is eligible for shadowing 137 * by this class loader. 138 * @param className the class name to check 139 * @return whether the specified class is eligible 140 * @see #isExcluded 141 */ 142 protected boolean isEligibleForShadowing(String className) { 143 return !isExcluded(className); 144 } 145 146 147 private Class<?> doLoadClass(String name) throws ClassNotFoundException { 148 String internalName = StringUtils.replace(name, ".", "/") + ".class"; 149 InputStream is = this.enclosingClassLoader.getResourceAsStream(internalName); 150 if (is == null) { 151 throw new ClassNotFoundException(name); 152 } 153 try { 154 byte[] bytes = FileCopyUtils.copyToByteArray(is); 155 bytes = applyTransformers(name, bytes); 156 Class<?> cls = defineClass(name, bytes, 0, bytes.length); 157 // Additional check for defining the package, if not defined yet. 158 if (cls.getPackage() == null) { 159 int packageSeparator = name.lastIndexOf('.'); 160 if (packageSeparator != -1) { 161 String packageName = name.substring(0, packageSeparator); 162 definePackage(packageName, null, null, null, null, null, null, null); 163 } 164 } 165 this.classCache.put(name, cls); 166 return cls; 167 } 168 catch (IOException ex) { 169 throw new ClassNotFoundException("Cannot load resource for class [" + name + "]", ex); 170 } 171 } 172 173 private byte[] applyTransformers(String name, byte[] bytes) { 174 String internalName = StringUtils.replace(name, ".", "/"); 175 try { 176 for (ClassFileTransformer transformer : this.classFileTransformers) { 177 byte[] transformed = transformer.transform(this, internalName, null, null, bytes); 178 bytes = (transformed != null ? transformed : bytes); 179 } 180 return bytes; 181 } 182 catch (IllegalClassFormatException ex) { 183 throw new IllegalStateException(ex); 184 } 185 } 186 187 188 @Override 189 public URL getResource(String name) { 190 return this.enclosingClassLoader.getResource(name); 191 } 192 193 @Override 194 @Nullable 195 public InputStream getResourceAsStream(String name) { 196 return this.enclosingClassLoader.getResourceAsStream(name); 197 } 198 199 @Override 200 public Enumeration<URL> getResources(String name) throws IOException { 201 return this.enclosingClassLoader.getResources(name); 202 } 203 204}