| // Copyright 2011 Google Inc. All Rights Reserved. |
| // |
| // 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.adaptor; |
| |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.List; |
| import java.util.Map; |
| |
| /** |
| * Modify metadata using multiple serial transforms. The transforms |
| * are arranged into a serial pipeline where the output of one becomes the |
| * input for the next in the series. |
| * |
| * <p>This class is thread-safe. |
| */ |
| class TransformPipeline { |
| private final List<DocumentTransform> transformList; |
| private final List<String> names; |
| |
| public TransformPipeline(List<? extends DocumentTransform> transforms, List<String> names) { |
| if (transforms.size() != names.size()) { |
| throw new IllegalArgumentException("Transforms and names must be the same size"); |
| } |
| this.transformList = Collections.unmodifiableList(new ArrayList<DocumentTransform>(transforms)); |
| this.names = Collections.unmodifiableList(new ArrayList<String>(names)); |
| // Check for null after copying the lists because List.contains(null) is permitted to throw NPE |
| // whereas ArrayList is documented not to throw NPE. |
| if (transformList.contains(null)) { |
| throw new NullPointerException("Transforms must not contain null values"); |
| } |
| if (names.contains(null)) { |
| throw new NullPointerException("Names must not contain null values"); |
| } |
| } |
| |
| /** |
| * Transform {@code metadata}. |
| */ |
| public void transform(Metadata metadata, Map<String, String> params) { |
| if (transformList.isEmpty()) { |
| return; |
| } |
| |
| Metadata metadataInTransit = new Metadata(metadata); |
| Map<String, String> paramsInTransit = Collections.checkedMap( |
| new HashMap<String, String>(params), String.class, String.class); |
| |
| for (int i = 0; i < transformList.size(); i++) { |
| DocumentTransform transform = transformList.get(i); |
| try { |
| transform.transform(metadataInTransit, paramsInTransit); |
| } catch (RuntimeException e) { |
| throw new RuntimeException( |
| "Exception during transform " + names.get(i), e); |
| } |
| } |
| |
| metadata.set(metadataInTransit); |
| params.clear(); |
| params.putAll(paramsInTransit); |
| } |
| |
| /** |
| * Retrieve transforms in the order they are processed in the pipeline. |
| */ |
| public List<DocumentTransform> getDocumentTransforms() { |
| return transformList; |
| } |
| |
| public List<String> getNames() { |
| return names; |
| } |
| } |