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/*
* Copyright 2002-2015 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.tomcat;
import java.lang.instrument.ClassFileTransformer;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import org.apache.catalina.loader.ResourceEntry;
import org.apache.catalina.loader.WebappClassLoader;
import org.springframework.instrument.classloading.WeavingTransformer;
/**
* Extension of Tomcat's default class loader which adds instrumentation
* to loaded classes without the need to use a VM-wide agent.
*
* <p>To be registered using a
* <a href="http://tomcat.apache.org/tomcat-6.0-doc/config/loader.html">{@code Loader}</a> tag
* in Tomcat's <a href="http://tomcat.apache.org/tomcat-6.0-doc/config/context.html">{@code Context}</a>
* definition in the {@code server.xml} file, with the Spring-provided "spring-instrument-tomcat.jar"
* file deployed into Tomcat's "lib" directory. The required configuration tag looks as follows:
*
* <pre class="code"><Loader loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader"/></pre>
*
* <p>Typically used in combination with a
* {@link org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver}
* defined in the Spring application context. The {@code addTransformer} and
* {@code getThrowawayClassLoader} methods mirror the corresponding methods
* in the LoadTimeWeaver interface, as expected by ReflectiveLoadTimeWeaver.
*
* <p><b>NOTE:</b> Requires Apache Tomcat version 6.0 or higher, as of Spring 4.0.
* This class is not intended to work on Tomcat 8.0+; please rely on Tomcat's own
* {@code InstrumentableClassLoader} facility instead, as autodetected by Spring's
* {@link org.springframework.instrument.classloading.tomcat.TomcatLoadTimeWeaver}.
*
* @author Costin Leau
* @author Juergen Hoeller
* @since 2.0
* @see #addTransformer
* @see #getThrowawayClassLoader
* @see org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver
* @see org.springframework.instrument.classloading.tomcat.TomcatLoadTimeWeaver
*/
public class TomcatInstrumentableClassLoader extends WebappClassLoader {
private static final String CLASS_SUFFIX = ".class";
/** Use an internal WeavingTransformer */
private final WeavingTransformer weavingTransformer;
/**
* Create a new {@code TomcatInstrumentableClassLoader} using the
* current context class loader.
* @see #TomcatInstrumentableClassLoader(ClassLoader)
*/
public TomcatInstrumentableClassLoader() {
super();
this.weavingTransformer = new WeavingTransformer(this);
}
/**
* Create a new {@code TomcatInstrumentableClassLoader} with the
* supplied class loader as parent.
* @param parent the parent {@link ClassLoader} to be used
*/
public TomcatInstrumentableClassLoader(ClassLoader parent) {
super(parent);
this.weavingTransformer = new WeavingTransformer(this);
}
/**
* Delegate for LoadTimeWeaver's {@code addTransformer} method.
* Typically called through ReflectiveLoadTimeWeaver.
* @see org.springframework.instrument.classloading.LoadTimeWeaver#addTransformer
* @see org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver
*/
public void addTransformer(ClassFileTransformer transformer) {
this.weavingTransformer.addTransformer(transformer);
}
/**
* Delegate for LoadTimeWeaver's {@code getThrowawayClassLoader} method.
* Typically called through ReflectiveLoadTimeWeaver.
* @see org.springframework.instrument.classloading.LoadTimeWeaver#getThrowawayClassLoader
* @see org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver
*/
public ClassLoader getThrowawayClassLoader() {
WebappClassLoader tempLoader = new WebappClassLoader();
// Use reflection to copy all the fields since they are not exposed any other way.
shallowCopyFieldState(this, tempLoader);
return tempLoader;
}
@Override // overriding the pre-7.0.63 variant of findResourceInternal
protected ResourceEntry findResourceInternal(String name, String path) {
ResourceEntry entry = super.findResourceInternal(name, path);
if (entry != null && entry.binaryContent != null && path.endsWith(CLASS_SUFFIX)) {
String className = (name.endsWith(CLASS_SUFFIX) ? name.substring(0, name.length() - CLASS_SUFFIX.length()) : name);
entry.binaryContent = this.weavingTransformer.transformIfNecessary(className, entry.binaryContent);
}
return entry;
}
@Override // overriding the 7.0.63+ variant of findResourceInternal
protected ResourceEntry findResourceInternal(String name, String path, boolean manifestRequired) {
ResourceEntry entry = super.findResourceInternal(name, path, manifestRequired);
if (entry != null && entry.binaryContent != null && path.endsWith(CLASS_SUFFIX)) {
String className = (name.endsWith(CLASS_SUFFIX) ? name.substring(0, name.length() - CLASS_SUFFIX.length()) : name);
entry.binaryContent = this.weavingTransformer.transformIfNecessary(className, entry.binaryContent);
}
return entry;
}
@Override
public String toString() {
return getClass().getName() + "\r\n" + super.toString();
}
// The code below is originally taken from ReflectionUtils and optimized for
// local usage. There is no dependency on ReflectionUtils to keep this class
// self-contained (since it gets deployed into Tomcat's server class loader).
private static void shallowCopyFieldState(final WebappClassLoader src, final WebappClassLoader dest) {
Class<?> targetClass = WebappClassLoader.class;
// Keep backing up the inheritance hierarchy.
do {
Field[] fields = targetClass.getDeclaredFields();
for (Field field : fields) {
// Do not copy resourceEntries - it's a cache that holds class entries.
if (!(Modifier.isStatic(field.getModifiers()) || Modifier.isFinal(field.getModifiers()) ||
field.getName().equals("resourceEntries"))) {
try {
field.setAccessible(true);
Object srcValue = field.get(src);
field.set(dest, srcValue);
}
catch (IllegalAccessException ex) {
throw new IllegalStateException(
"Shouldn't be illegal to access field '" + field.getName() + "': " + ex);
}
}
}
targetClass = targetClass.getSuperclass();
}
while (targetClass != null && targetClass != Object.class);
}
}
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