001    // Copyright 2007 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.services;
016    
017    import org.apache.tapestry5.annotations.Environmental;
018    import org.apache.tapestry5.ioc.services.PropertyShadowBuilder;
019    
020    /**
021     * Much like {@link PropertyShadowBuilder}, except that instead of accessing a property of some other service, it
022     * accesses a value from within the {@link Environment} service. This is useful for defining a new service that can be
023     * injected into other services (whereas the {@link Environmental} annotation may only be used within component
024     * classes).
025     */
026    public interface EnvironmentalShadowBuilder
027    {
028        /**
029         * Returns a proxy that delegates all methods to an object obtained from {@link Environment#peekRequired(Class)}.
030         * Note that at the time this method is invoked, the Environment service may still be virtual, and will often not
031         * yet have been loaded with values, and that's OK, the resolution is deferred to the instant a method is invoked.
032         *
033         * @param <T>
034         * @param serviceType the service type, which is used to obtained the delegate instance
035         * @return a proxy to the service
036         */
037        <T> T build(Class<T> serviceType);
038    }