001/*
002 * Copyright 2002-2012 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.lang.instrument.ClassFileTransformer;
020
021/**
022 * Defines the contract for adding one or more
023 * {@link ClassFileTransformer ClassFileTransformers} to a {@link ClassLoader}.
024 *
025 * <p>Implementations may operate on the current context {@code ClassLoader}
026 * or expose their own instrumentable {@code ClassLoader}.
027 *
028 * @author Rod Johnson
029 * @author Costin Leau
030 * @since 2.0
031 * @see java.lang.instrument.ClassFileTransformer
032 */
033public interface LoadTimeWeaver {
034
035        /**
036         * Add a {@code ClassFileTransformer} to be applied by this
037         * {@code LoadTimeWeaver}.
038         * @param transformer the {@code ClassFileTransformer} to add
039         */
040        void addTransformer(ClassFileTransformer transformer);
041
042        /**
043         * Return a {@code ClassLoader} that supports instrumentation
044         * through AspectJ-style load-time weaving based on user-defined
045         * {@link ClassFileTransformer ClassFileTransformers}.
046         * <p>May be the current {@code ClassLoader}, or a {@code ClassLoader}
047         * created by this {@link LoadTimeWeaver} instance.
048         * @return the {@code ClassLoader} which will expose
049         * instrumented classes according to the registered transformers
050         */
051        ClassLoader getInstrumentableClassLoader();
052
053        /**
054         * Return a throwaway {@code ClassLoader}, enabling classes to be
055         * loaded and inspected without affecting the parent {@code ClassLoader}.
056         * <p>Should <i>not</i> return the same instance of the {@link ClassLoader}
057         * returned from an invocation of {@link #getInstrumentableClassLoader()}.
058         * @return a temporary throwaway {@code ClassLoader}; should return
059         * a new instance for each call, with no existing state
060         */
061        ClassLoader getThrowawayClassLoader();
062
063}