001/*
002 * Copyright 2002-2017 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.util.Assert;
032import org.springframework.util.FileCopyUtils;
033import org.springframework.util.StringUtils;
034
035/**
036 * ClassLoader decorator that shadows an enclosing ClassLoader,
037 * applying registered transformers to all affected classes.
038 *
039 * @author Rob Harrop
040 * @author Juergen Hoeller
041 * @author Costin Leau
042 * @since 2.0
043 * @see #addTransformer
044 * @see org.springframework.core.OverridingClassLoader
045 */
046public class ShadowingClassLoader extends DecoratingClassLoader {
047
048        /** Packages that are excluded by default */
049        public static final String[] DEFAULT_EXCLUDED_PACKAGES =
050                        new String[] {"java.", "javax.", "sun.", "oracle.", "com.sun.", "com.ibm.", "COM.ibm.",
051                                        "org.w3c.", "org.xml.", "org.dom4j.", "org.eclipse", "org.aspectj.", "net.sf.cglib",
052                                        "org.springframework.cglib", "org.apache.xerces.", "org.apache.commons.logging."};
053
054
055        private final ClassLoader enclosingClassLoader;
056
057        private final List<ClassFileTransformer> classFileTransformers = new LinkedList<ClassFileTransformer>();
058
059        private final Map<String, Class<?>> classCache = new HashMap<String, Class<?>>();
060
061
062        /**
063         * Create a new ShadowingClassLoader, decorating the given ClassLoader,
064         * applying {@link #DEFAULT_EXCLUDED_PACKAGES}.
065         * @param enclosingClassLoader the ClassLoader to decorate
066         * @see #ShadowingClassLoader(ClassLoader, boolean)
067         */
068        public ShadowingClassLoader(ClassLoader enclosingClassLoader) {
069                this(enclosingClassLoader, true);
070        }
071
072        /**
073         * Create a new ShadowingClassLoader, decorating the given ClassLoader.
074         * @param enclosingClassLoader the ClassLoader to decorate
075         * @param defaultExcludes whether to apply {@link #DEFAULT_EXCLUDED_PACKAGES}
076         * @since 4.3.8
077         */
078        public ShadowingClassLoader(ClassLoader enclosingClassLoader, boolean defaultExcludes) {
079                Assert.notNull(enclosingClassLoader, "Enclosing ClassLoader must not be null");
080                this.enclosingClassLoader = enclosingClassLoader;
081                if (defaultExcludes) {
082                        for (String excludedPackage : DEFAULT_EXCLUDED_PACKAGES) {
083                                excludePackage(excludedPackage);
084                        }
085                }
086        }
087
088
089        /**
090         * Add the given ClassFileTransformer to the list of transformers that this
091         * ClassLoader will apply.
092         * @param transformer the ClassFileTransformer
093         */
094        public void addTransformer(ClassFileTransformer transformer) {
095                Assert.notNull(transformer, "Transformer must not be null");
096                this.classFileTransformers.add(transformer);
097        }
098
099        /**
100         * Copy all ClassFileTransformers from the given ClassLoader to the list of
101         * transformers that this ClassLoader will apply.
102         * @param other the ClassLoader to copy from
103         */
104        public void copyTransformers(ShadowingClassLoader other) {
105                Assert.notNull(other, "Other ClassLoader must not be null");
106                this.classFileTransformers.addAll(other.classFileTransformers);
107        }
108
109
110        @Override
111        public Class<?> loadClass(String name) throws ClassNotFoundException {
112                if (shouldShadow(name)) {
113                        Class<?> cls = this.classCache.get(name);
114                        if (cls != null) {
115                                return cls;
116                        }
117                        return doLoadClass(name);
118                }
119                else {
120                        return this.enclosingClassLoader.loadClass(name);
121                }
122        }
123
124        /**
125         * Determine whether the given class should be excluded from shadowing.
126         * @param className the name of the class
127         * @return whether the specified class should be shadowed
128         */
129        private boolean shouldShadow(String className) {
130                return (!className.equals(getClass().getName()) && !className.endsWith("ShadowingClassLoader") &&
131                                isEligibleForShadowing(className));
132        }
133
134        /**
135         * Determine whether the specified class is eligible for shadowing
136         * by this class loader.
137         * @param className the class name to check
138         * @return whether the specified class is eligible
139         * @see #isExcluded
140         */
141        protected boolean isEligibleForShadowing(String className) {
142                return !isExcluded(className);
143        }
144
145
146        private Class<?> doLoadClass(String name) throws ClassNotFoundException {
147                String internalName = StringUtils.replace(name, ".", "/") + ".class";
148                InputStream is = this.enclosingClassLoader.getResourceAsStream(internalName);
149                if (is == null) {
150                        throw new ClassNotFoundException(name);
151                }
152                try {
153                        byte[] bytes = FileCopyUtils.copyToByteArray(is);
154                        bytes = applyTransformers(name, bytes);
155                        Class<?> cls = defineClass(name, bytes, 0, bytes.length);
156                        // Additional check for defining the package, if not defined yet.
157                        if (cls.getPackage() == null) {
158                                int packageSeparator = name.lastIndexOf('.');
159                                if (packageSeparator != -1) {
160                                        String packageName = name.substring(0, packageSeparator);
161                                        definePackage(packageName, null, null, null, null, null, null, null);
162                                }
163                        }
164                        this.classCache.put(name, cls);
165                        return cls;
166                }
167                catch (IOException ex) {
168                        throw new ClassNotFoundException("Cannot load resource for class [" + name + "]", ex);
169                }
170        }
171
172        private byte[] applyTransformers(String name, byte[] bytes) {
173                String internalName = StringUtils.replace(name, ".", "/");
174                try {
175                        for (ClassFileTransformer transformer : this.classFileTransformers) {
176                                byte[] transformed = transformer.transform(this, internalName, null, null, bytes);
177                                bytes = (transformed != null ? transformed : bytes);
178                        }
179                        return bytes;
180                }
181                catch (IllegalClassFormatException ex) {
182                        throw new IllegalStateException(ex);
183                }
184        }
185
186
187        @Override
188        public URL getResource(String name) {
189                return this.enclosingClassLoader.getResource(name);
190        }
191
192        @Override
193        public InputStream getResourceAsStream(String name) {
194                return this.enclosingClassLoader.getResourceAsStream(name);
195        }
196
197        @Override
198        public Enumeration<URL> getResources(String name) throws IOException {
199                return this.enclosingClassLoader.getResources(name);
200        }
201
202}