001// Copyright 2009 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.ioc.services;
016
017import org.apache.tapestry5.ioc.ObjectCreator;
018
019/**
020 * A <a href="http://en.wikipedia.org/wiki/Thunk">thunk</a> is a delayed calculation. In Java and Tapestry terms, a
021 * Thunk is a proxy object of a particular interface that delegates all methods to an object of the same type obtained
022 * from an {@link org.apache.tapestry5.ioc.ObjectProvider}. This is used by {@link
023 * org.apache.tapestry5.ioc.services.LazyAdvisor} to build lazy thunk proxies.
024 *
025 * @since 5.1.0.1
026 */
027public interface ThunkCreator
028{
029    /**
030     * Creates a Thunk of the given proxy type.
031     *
032     * @param proxyType     type of object to create (must be an interface)
033     * @param objectCreator provides an instance of the same type on demand (may be invoked multiple times)
034     * @param description   to be returned from the thunk's toString() method
035     * @param <T>           type of thunk
036     * @return thunk of given type
037     */
038    <T> T createThunk(Class<T> proxyType, ObjectCreator objectCreator, String description);
039}