    001// Copyright 2006, 2009, 2011, 2013 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;
    016
    017
    018/**
    019 * Similar to {@link Runnable} except that it returns a value. Used to represent any operation which can return a
    020 * value. This is often used in situations where the code is to be executed in another threads.
    021 *
    022 * @param <T> the return value type
    023 * @see org.apache.tapestry5.ioc.OperationTracker#invoke(String, Invokable)
    024 * @see org.apache.tapestry5.ioc.services.ParallelExecutor#invoke(Invokable)
    025 * @see IOOperation
    026 */
    027public interface Invokable<T>
    028{
    029    /**
    030     * Called to produce a value.
    031     */
    032    T invoke();
    033}