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
015package org.apache.tapestry5.ioc.services;
016
017import org.slf4j.Logger;
018
019import 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 */
038public 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}