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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *  http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.any23.extractor.html;
19  
20  import org.apache.any23.extractor.ExtractionException;
21  import org.apache.any23.extractor.ExtractionResult;
22  import org.apache.any23.rdf.RDFUtils;
23  import org.openrdf.model.BNode;
24  import org.w3c.dom.Node;
25  
26  import java.util.List;
27  
28  /**
29   * Base class for microformat extractors based on entities.
30   *
31   * @author Gabriele Renzi
32   */
33  public abstract class EntityBasedMicroformatExtractor extends MicroformatExtractor {
34  
35      /**
36       * Returns the base class name for the extractor.
37       *
38       * @return a string containing the base of the extractor.
39       */
40      protected abstract String getBaseClassName();
41  
42      /**
43       * Resets the internal status of the extractor to prepare it to a new extraction section.
44       */
45      protected abstract void resetExtractor();
46  
47      /**
48       * Extracts an entity from a <i>DOM</i> node.
49       *
50       * @param node the DOM node.
51       * @param out the extraction result collector.
52       * @return <code>true</code> if the extraction has produces something, <code>false</code> otherwise.
53       * @throws ExtractionException
54       */
55      protected abstract boolean extractEntity(Node node, ExtractionResult out) throws ExtractionException;
56  
57      @Override
58      public boolean extract() throws ExtractionException {
59          List<Node> nodes = DomUtils.findAllByClassName( getHTMLDocument().getDocument(), getBaseClassName());
60          boolean foundAny = false;
61          int count = 1;
62          for (Node node : nodes) {
63              resetExtractor();
64              String contextID = Integer.toString(count);
65              ExtractionResult subResult = openSubResult( getExtractionContext().copy(contextID) );
66              foundAny |= extractEntity(node, subResult);
67              subResult.close();
68              count++;
69          }
70          return foundAny;
71      }
72  
73      /**
74       * @param node a DOM node representing a blank node
75       * @return an RDF blank node corresponding to that DOM node, by using a
76       *         blank node ID like "MD5 of http://doc-uri/#xpath/to/node"
77       */
78      protected BNode getBlankNodeFor(Node node) {
79          return RDFUtils.getBNode(getDocumentURI() + "#" + DomUtils.getXPathForNode(node));
80      }
81      
82  }