001// Copyright 2011, 2012 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.plastic;
016
017/**
018 * Allows a listener to be notified about classes about to be loaded by the manager's class loader.
019 * Some classes are loaded by the same class loader but not transformed (for example, inner classes). These
020 * do not generate events. In many cases, transforming a class will cause supporting classes (representing
021 * {@link MethodInvocation}s, and other things) to be created; these do generate events, and can be distinguished
022 * by the {@linkplain PlasticClassEvent#getType() event's type property}.
023 * 
024 * @see PlasticClassListenerHub
025 */
026public interface PlasticClassListener
027{
028    /**
029     * Invoked just before a class is to be loaded. Separate events are fired for supporting classes before
030     * the event for the primary class (the class being transformed or created from scratch).
031     * 
032     * @param event
033     *            describes the class to be loaded, and gives access to its disassembled
034     *            bytecode (for debugging purposes)
035     */
036    void classWillLoad(PlasticClassEvent event);
037}