    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
    015    package 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     */
    025    public 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    }