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    
015    package org.apache.tapestry5.ioc.services;
016    
017    import 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     */
027    public 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    }