    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    import java.util.List;
    018
    019    /**
    020     * A service which can assemble an implementation based on a command interface, and an ordered list of objects
    021     * implementing that interface (the "commands"). This is an implementation of the Gang of Four Chain Of Command
    022     * pattern.
    023     * <p/>
    024     * For each method in the interface, the chain implementation will call the corresponding method on each command object
    025     * in turn (with the order defined by the list). If any of the command objects return true, then the chain of command
    026     * stops and the initial method invocation returns true. Otherwise, the chain of command continues to the next command
    027     * (and will return false if none of the commands returns true).
    028     * <p/>
    029     * For methods whose return type is not boolean, the chain stops with the first non-null (for object types), or non-zero
    030     * (for numeric types). The chain returns the value that was returned by the command. If the method return type is void,
    031     * all commands will be invoked.
    032     * <p/>
    033     * Method invocations will also be terminated if an exception is thrown.
    034     */
    035    public interface ChainBuilder
    036    {
    037        /**
    038         * Creates a chain instance from a command interface and a list of commands (implementing the interface).
    039         */
    040        <T> T build(Class<T> commandInterface, List<T> commands);
    041    }