    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.ioc.services;
    014
    015/**
    016 * Creates a "shadow" of a property of an object. The shadow has the same type as the property, and delegates all method
    017 * invocations to the property. Each method invocation on the shadow re-acquires the value of the property from the
    018 * underlying object and delegates to the current value of the property.
    019 *
    020 * Typically, the object in question is another service, one with the "perthread" service lifecycle. This allows a
    021 * global singleton to shadow a value that is specific to the current thread (and therefore, the current request).
    022 */
    023public interface PropertyShadowBuilder
    024{
    025    /**
    026     * @param <T>
    027     * @param source       the object from which a property will be extracted
    028     * @param propertyName the name of a property of the object, which must be readable
    029     * @param propertyType the expected type of the property, the actual property type must be assignable to this type
    030     * @return the shadow
    031     */
    032    <T> T build(Object source, String propertyName, Class<T> propertyType);
    033}