    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}