/*
* Copyright 2002-2008 the original author or authors.
*
* Licensed 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.springframework.instrument.classloading;
import java.io.IOException;
import java.io.InputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import org.springframework.core.DecoratingClassLoader;
import org.springframework.util.Assert;
import org.springframework.util.FileCopyUtils;
import org.springframework.util.StringUtils;
/**
* ClassLoader decorator that shadows an enclosing ClassLoader,
* applying registered transformers to all affected classes.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Costin Leau
* @since 2.0
* @see #addTransformer
* @see org.springframework.core.OverridingClassLoader
*/
public class ShadowingClassLoader extends DecoratingClassLoader {
/** Packages that are excluded by default */
public static final String[] DEFAULT_EXCLUDED_PACKAGES =
new String[] {"java.", "javax.", "sun.", "oracle.", "com.sun.", "com.ibm.", "COM.ibm.",
"org.w3c.", "org.xml.", "org.dom4j.", "org.eclipse", "org.aspectj.", "net.sf.cglib.",
"org.apache.xerces.", "org.apache.commons.logging."};
private final ClassLoader enclosingClassLoader;
private final List<ClassFileTransformer> classFileTransformers = new LinkedList<ClassFileTransformer>();
private final Map<String, Class> classCache = new HashMap<String, Class>();
/**
* Create a new ShadowingClassLoader, decorating the given ClassLoader.
* @param enclosingClassLoader the ClassLoader to decorate
*/
public ShadowingClassLoader(ClassLoader enclosingClassLoader) {
Assert.notNull(enclosingClassLoader, "Enclosing ClassLoader must not be null");
this.enclosingClassLoader = enclosingClassLoader;
for (int i = 0; i < DEFAULT_EXCLUDED_PACKAGES.length; i++) {
excludePackage(DEFAULT_EXCLUDED_PACKAGES[i]);
}
}
/**
* Add the given ClassFileTransformer to the list of transformers that this
* ClassLoader will apply.
* @param transformer the ClassFileTransformer
*/
public void addTransformer(ClassFileTransformer transformer) {
Assert.notNull(transformer, "Transformer must not be null");
this.classFileTransformers.add(transformer);
}
/**
* Copy all ClassFileTransformers from the given ClassLoader to the list of
* transformers that this ClassLoader will apply.
* @param other the ClassLoader to copy from
*/
public void copyTransformers(ShadowingClassLoader other) {
Assert.notNull(other, "Other ClassLoader must not be null");
this.classFileTransformers.addAll(other.classFileTransformers);
}
public Class<?> loadClass(String name) throws ClassNotFoundException {
if (shouldShadow(name)) {
Class cls = this.classCache.get(name);
if (cls != null) {
return cls;
}
return doLoadClass(name);
}
else {
return this.enclosingClassLoader.loadClass(name);
}
}
/**
* Determine whether the given class should be excluded from shadowing.
* @param className the name of the class
* @return whether the specified class should be shadowed
*/
private boolean shouldShadow(String className) {
return (!className.equals(getClass().getName()) && !className.endsWith("ShadowingClassLoader")
&& isEligibleForShadowing(className) && !isClassNameExcludedFromShadowing(className));
}
/**
* Determine whether the specified class is eligible for shadowing
* by this class loader.
* @param className the class name to check
* @return whether the specified class is eligible
* @see #isExcluded
*/
protected boolean isEligibleForShadowing(String className) {
return !isExcluded(className);
}
/**
* Subclasses can override this method to specify whether or not a
* particular class should be excluded from shadowing.
* @param className the class name to test
* @return whether the specified class is excluded
* @deprecated in favor of {@link #isEligibleForShadowing}
*/
protected boolean isClassNameExcludedFromShadowing(String className) {
return false;
}
private Class doLoadClass(String name) throws ClassNotFoundException {
String internalName = StringUtils.replace(name, ".", "/") + ".class";
InputStream is = this.enclosingClassLoader.getResourceAsStream(internalName);
if (is == null) {
throw new ClassNotFoundException(name);
}
try {
byte[] bytes = FileCopyUtils.copyToByteArray(is);
bytes = applyTransformers(name, bytes);
Class cls = defineClass(name, bytes, 0, bytes.length);
// Additional check for defining the package, if not defined yet.
if (cls.getPackage() == null) {
int packageSeparator = name.lastIndexOf('.');
if (packageSeparator != -1) {
String packageName = name.substring(0, packageSeparator);
definePackage(packageName, null, null, null, null, null, null, null);
}
}
this.classCache.put(name, cls);
return cls;
}
catch (IOException ex) {
throw new ClassNotFoundException("Cannot load resource for class [" + name + "]", ex);
}
}
private byte[] applyTransformers(String name, byte[] bytes) {
String internalName = StringUtils.replace(name, ".", "/");
try {
for (ClassFileTransformer transformer : this.classFileTransformers) {
byte[] transformed = transformer.transform(this, internalName, null, null, bytes);
bytes = (transformed != null ? transformed : bytes);
}
return bytes;
}
catch (IllegalClassFormatException ex) {
throw new IllegalStateException(ex);
}
}
public URL getResource(String name) {
return this.enclosingClassLoader.getResource(name);
}
public InputStream getResourceAsStream(String name) {
return this.enclosingClassLoader.getResourceAsStream(name);
}
public Enumeration<URL> getResources(String name) throws IOException {
return this.enclosingClassLoader.getResources(name);
}
}