    001    // Copyright 2006, 2007, 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.services;
    016
    017    import org.slf4j.Logger;
    018
    019    import java.util.List;
    020
    021    /**
    022     * Creates a pipeline from a service interface and an ordered list of filters. Each filter is defined in terms of a
    023     * filter interface: the filter interface is a variant of the service interface, where each method has an additional
    024     * parameter that is an instance of the service interface. Typically, this service parameter (often named "delegate") is
    025     * either the first or the last parameter of each method.
    026     * <p/>
    027     * The implementation of a filter method is expected to pass all of its parameters to the service instance passed into
    028     * it.
    029     * <p/>
    030     * The interesting thing is that there may be multiple filters in the pipeline. A fabricated "bridge" object (that
    031     * implements the service interface) is created to let each filter invoke methods on the next filter down the pipeline.
    032     * This simplifies the model for creating pipelines, as each filter is coded as if it was directly "in front of" the
    033     * terminator. In fact, it may be indirectly invoking methods on the next filter in the pipeline via a bridge instance.
    034     * <p/>
    035     * The builder is fairly smart about matching up service interface methods to filter interface methods, but keeping it
    036     * simple is also a good idea.  By convention, the final parameter of each filter method is the delegate object (the bridge or terminator).
    037     */
    038    public interface PipelineBuilder
    039    {
    040        /**
    041         * Creates a pipeline from the filters and a terminator.
    042         *
    043         * @param <S>              service type
    044         * @param <F>              filter type
    045         * @param logger           logs any warnings generated when constructing the pipeline
    046         * @param serviceInterface defines the interface for the pipeline
    047         * @param filterInterface  the filter interface, contributed into the pipeline
    048         * @param filters          sorted list of filters
    049         * @param terminator       end of the pipeline
    050         * @return an object that encapsulates the filters and the terminator
    051         */
    052        <S, F> S build(Logger logger, Class<S> serviceInterface, Class<F> filterInterface, List<F> filters, S terminator);
    053
    054        /**
    055         * Creates a pipeline from just the filters. A {@link DefaultImplementationBuilder default implementation} is
    056         * created as the terminator.
    057         *
    058         * @param <S>              service type
    059         * @param <F>              filter type
    060         * @param logger           logs any warnings generated when constructing the pipeline
    061         * @param serviceInterface defines the interface for the pipeline
    062         * @param filterInterface  the filter interface, contributed into the pipeline
    063         * @param filters          sorted list of filters
    064         * @return an object that encapsulates the filters and the default implementation
    065         */
    066        <S, F> S build(Logger logger, Class<S> serviceInterface, Class<F> filterInterface, List<F> filters);
    067
    068    }