    001    // Copyright 2006, 2009, 2011 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;
    016
    017
    018    /**
    019     * Similiar to {@link Runnable} execept 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     */
    026    public interface Invokable<T>
    027    {
    028        /**
    029         * Called to produce a value.
    030         */
    031        T invoke();
    032    }