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}