org.broadleafcommerce.common.extensibility.jpa.BroadleafLoadTimeWeaver Maven / Gradle / Ivy

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/*
 * Copyright 2008-2009 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.broadleafcommerce.common.extensibility.jpa;

import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.List;

import org.broadleafcommerce.instrument.BroadleafInstrumentationSavingAgent;
import org.springframework.instrument.classloading.LoadTimeWeaver;
import org.springframework.instrument.classloading.SimpleThrowawayClassLoader;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * Based on org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver from Spring 3.0.5 by Rod Johnson and Juergen Hoeller
 * 
 * @author jfischer
 *
 */
public class BroadleafLoadTimeWeaver implements LoadTimeWeaver {

	private static final boolean AGENT_CLASS_PRESENT = ClassUtils.isPresent(
			"org.broadleafcommerce.instrument.BroadleafInstrumentationSavingAgent",
			BroadleafLoadTimeWeaver.class.getClassLoader());

	private final ClassLoader classLoader;

	private final Instrumentation instrumentation;

	private final List transformers = new ArrayList(4);


	/**
	 * Create a new InstrumentationLoadTimeWeaver for the default ClassLoader.
	 */
	public BroadleafLoadTimeWeaver() {
		this(ClassUtils.getDefaultClassLoader());
	}

	/**
	 * Create a new InstrumentationLoadTimeWeaver for the given ClassLoader.
	 * @param classLoader the ClassLoader that registered transformers are supposed to apply to
	 */
	public BroadleafLoadTimeWeaver(ClassLoader classLoader) {
		Assert.notNull(classLoader, "ClassLoader must not be null");
		this.classLoader = classLoader;
		this.instrumentation = getInstrumentation();
	}


	public void addTransformer(ClassFileTransformer transformer) {
		Assert.notNull(transformer, "Transformer must not be null");
		FilteringClassFileTransformer actualTransformer =
				new FilteringClassFileTransformer(transformer, this.classLoader);
		synchronized (this.transformers) {
			if (this.instrumentation == null) {
				throw new IllegalStateException(
						"Must start with Java agent to use InstrumentationLoadTimeWeaver. See Spring documentation.");
			}
			this.instrumentation.addTransformer(actualTransformer, true);
			this.transformers.add(actualTransformer);
		}
	}

	/**
	 * We have the ability to weave the current class loader when starting the
	 * JVM in this way, so the instrumentable class loader will always be the
	 * current loader.
	 */
	public ClassLoader getInstrumentableClassLoader() {
		return this.classLoader;
	}

	/**
	 * This implementation always returns a {@link SimpleThrowawayClassLoader}.
	 */
	public ClassLoader getThrowawayClassLoader() {
		return new SimpleThrowawayClassLoader(getInstrumentableClassLoader());
	}

	/**
	 * Remove all registered transformers, in inverse order of registration.
	 */
	public void removeTransformers() {
		synchronized (this.transformers) {
			if (!this.transformers.isEmpty()) {
				for (int i = this.transformers.size() - 1; i >= 0; i--) {
					this.instrumentation.removeTransformer(this.transformers.get(i));
				}
				this.transformers.clear();
			}
		}
	}


	/**
	 * Check whether an Instrumentation instance is available for the current VM.
	 * @see #getInstrumentation()
	 */
	public static boolean isInstrumentationAvailable() {
		return (getInstrumentation() != null);
	}

	/**
	 * Obtain the Instrumentation instance for the current VM, if available.
	 * @return the Instrumentation instance, or null if none found
	 * @see #isInstrumentationAvailable()
	 */
	protected static Instrumentation getInstrumentation() {
		if (AGENT_CLASS_PRESENT) {
			return InstrumentationAccessor.getInstrumentation();
		}
		else {
			return null;
		}
	}


	/**
	 * Inner class to avoid InstrumentationSavingAgent dependency.
	 */
	private static class InstrumentationAccessor {

		public static Instrumentation getInstrumentation() {
			return BroadleafInstrumentationSavingAgent.getInstrumentation();
		}
	}


	/**
	 * Decorator that only applies the given target transformer to a specific ClassLoader.
	 */
	private static class FilteringClassFileTransformer implements ClassFileTransformer {

		private final ClassFileTransformer targetTransformer;

		private final ClassLoader targetClassLoader;

		public FilteringClassFileTransformer(ClassFileTransformer targetTransformer, ClassLoader targetClassLoader) {
			this.targetTransformer = targetTransformer;
			this.targetClassLoader = targetClassLoader;
		}

		public byte[] transform(ClassLoader loader, String className, Class classBeingRedefined,
				ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {

			if (!this.targetClassLoader.equals(loader)) {
				return null;
			}
			return this.targetTransformer.transform(
					loader, className, classBeingRedefined, protectionDomain, classfileBuffer);
		}

		@Override
		public String toString() {
			return "FilteringClassFileTransformer for: " + this.targetTransformer.toString();
		}
	}
}