/*
 * Copyright 2002-2006 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.lang.instrument.ClassFileTransformer;

/**
 * Defines the contract for adding one or more
 * {@link ClassFileTransformer ClassFileTransformers} to a
 * {@link ClassLoader class loader} - typically the current context class
 * loader.
 * 
 * <p>Implementations may of course provide their own class loader as well.
 *
 * @author Rod Johnson
 * @author Costin Leau
 * @since 2.0
 */
public interface LoadTimeWeaver {

	/**
	 * Add a class file transformer to be applied by this load time weaver.
	 * @param transformer the class file transformer to add
	 */
	void addTransformer(ClassFileTransformer transformer);
	
	/**
	 * Return a class loader that supports instrumentation through AspectJ-style
	 * load time weaving based on user-defined
	 * {@link ClassFileTransformer ClassFileTransformers}.
	 * <p>May be the current class loader, or a class loader created by this
	 * {@link LoadTimeWeaver} instance.
	 * @return a class loader that supports instrumentation through AspectJ-style
	 * load time weaving based on user-defined
	 * {@link ClassFileTransformer ClassFileTransformers}
	 */
	ClassLoader getInstrumentableClassLoader();
	
	/**
	 * Return a throwaway class loader, enabling classes to be loaded and
	 * inspected without affecting the parent class loader.
	 * <p>Should <i>not</i> return the same instance of the {@link ClassLoader}
	 * returned from an invocation of {@link #getInstrumentableClassLoader()}.
	 * @return a temporary throwaway class loader; should return a new
	 * instance for each call, with no existing state
	 */
	ClassLoader getThrowawayClassLoader();

}