// Copyright 2011 Google Inc. // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package com.google.enterprise.connector.util.filter; import com.google.common.base.Preconditions; import com.google.enterprise.connector.spi.Document; import com.google.enterprise.connector.spi.RepositoryException; import java.util.Collections; import java.util.List; /** * {@link DocumentFilterChain} constructs a chain of {@link Document} * filters. The filters are constructed from a {@link List} of * {@link DocumentFilterFactory DocumentFilterFactories}, and linked * together like pop-beads, each using the previous as its source Document. * * @since 2.8 */ public class DocumentFilterChain implements DocumentFilterFactory { // The list of factories used to construct the filter chain. private final List<? extends DocumentFilterFactory> factories; /** * Constructs an empty {@link DocumentFilterChain}. Documents will * will pass through unchanged. */ public DocumentFilterChain() { this.factories = Collections.emptyList(); } /** * Constructs a {@link DocumentFilterChain} that uses the supplied * List of {@link DocumentFilterFactory DocumentFilterFactories} * assemble a document filter chain. * * @param factories a List of {@link DocumentFilterFactory} */ public DocumentFilterChain(List<? extends DocumentFilterFactory> factories) { Preconditions.checkNotNull(factories); this.factories = factories; } /** * Constructs a document procssing pipeline, assembled from filters fetched * from each of the {@link DocumentFilterFactory DocumentFilterFactories} * in the list. Returns the head of the chain. The supplied {@code source} * Document will be the input for the tail of the chain. * * @param source the input {@link Document} for the filters * @return the head of the chain of filters */ @Override public Document newDocumentFilter(Document source) throws RepositoryException { Preconditions.checkNotNull(source); for (DocumentFilterFactory factory : factories) { source = factory.newDocumentFilter(source); } return source; } @Override public String toString() { return "DocumentFilterChain: " + factories.toString(); } }