    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.ioc.services;
    014
    015import org.slf4j.Logger;
    016
    017import java.util.List;
    018
    019/**
    020 * Creates a pipeline from a service interface and an ordered list of filters. Each filter is defined in terms of a
    021 * filter interface: the filter interface is a variant of the service interface, where each method has an additional
    022 * parameter that is an instance of the service interface. Typically, this service parameter (often named "delegate") is
    023 * either the first or the last parameter of each method.
    024 *
    025 * The implementation of a filter method is expected to pass all of its parameters to the service instance passed into
    026 * it.
    027 *
    028 * The interesting thing is that there may be multiple filters in the pipeline. A fabricated "bridge" object (that
    029 * implements the service interface) is created to let each filter invoke methods on the next filter down the pipeline.
    030 * This simplifies the model for creating pipelines, as each filter is coded as if it was directly "in front of" the
    031 * terminator. In fact, it may be indirectly invoking methods on the next filter in the pipeline via a bridge instance.
    032 *
    033 * The builder is fairly smart about matching up service interface methods to filter interface methods, but keeping it
    034 * simple is also a good idea.  By convention, the final parameter of each filter method is the delegate object (the bridge or terminator).
    035 */
    036public interface PipelineBuilder
    037{
    038    /**
    039     * Creates a pipeline from the filters and a terminator.
    040     *
    041     * @param <S>              service type
    042     * @param <F>              filter type
    043     * @param logger           logs any warnings generated when constructing the pipeline
    044     * @param serviceInterface defines the interface for the pipeline
    045     * @param filterInterface  the filter interface, contributed into the pipeline
    046     * @param filters          sorted list of filters
    047     * @param terminator       end of the pipeline
    048     * @return an object that encapsulates the filters and the terminator
    049     */
    050    <S, F> S build(Logger logger, Class<S> serviceInterface, Class<F> filterInterface, List<F> filters, S terminator);
    051
    052    /**
    053     * Creates a pipeline from just the filters. A {@link DefaultImplementationBuilder default implementation} is
    054     * created as the terminator.
    055     *
    056     * @param <S>              service type
    057     * @param <F>              filter type
    058     * @param logger           logs any warnings generated when constructing the pipeline
    059     * @param serviceInterface defines the interface for the pipeline
    060     * @param filterInterface  the filter interface, contributed into the pipeline
    061     * @param filters          sorted list of filters
    062     * @return an object that encapsulates the filters and the default implementation
    063     */
    064    <S, F> S build(Logger logger, Class<S> serviceInterface, Class<F> filterInterface, List<F> filters);
    065
    066}