001// Copyright 2006 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
017/**
018 * Creates a "shadow" of a property of an object. The shadow has the same type as the property, and delegates all method
019 * invocations to the property. Each method invocation on the shadow re-acquires the value of the property from the
020 * underlying object and delegates to the current value of the property.
021 * <p/>
022 * Typically, the object in question is another service, one with the "perthread" service lifecycle. This allows a
023 * global singleton to shadow a value that is specific to the current thread (and therefore, the current request).
024 */
025public interface PropertyShadowBuilder
026{
027    /**
028     * @param <T>
029     * @param source       the object from which a property will be extracted
030     * @param propertyName the name of a property of the object, which must be readable
031     * @param propertyType the expected type of the property, the actual property type must be assignable to this type
032     * @return the shadow
033     */
034    <T> T build(Object source, String propertyName, Class<T> propertyType);
035}