src/plugin/creativecommons/src/java/org/creativecommons/nutch/CCIndexingFilter.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.creativecommons.nutch;

import org.apache.avro.util.Utf8;
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.indexer.IndexingException;
import org.apache.nutch.indexer.IndexingFilter;
import org.apache.nutch.indexer.NutchDocument;
import org.apache.nutch.metadata.CreativeCommons;
import org.apache.nutch.storage.WebPage;
import org.apache.nutch.storage.WebPage.Field;
import org.apache.nutch.util.Bytes;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.MalformedURLException;
import java.net.URL;
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.HashSet;
import java.util.StringTokenizer;

/** Adds basic searchable fields to a document. */
public class CCIndexingFilter implements IndexingFilter {
  public static final Logger LOG = LoggerFactory
      .getLogger(CCIndexingFilter.class);

  /** The name of the document field we use. */
  public static String FIELD = "cc";

  private Configuration conf;

  private static final Collection<WebPage.Field> FIELDS = new HashSet<WebPage.Field>();

  static {
    FIELDS.add(WebPage.Field.BASE_URL);
    FIELDS.add(WebPage.Field.METADATA);
  }

  /**
   * Add the features represented by a license URL. Urls are of the form
   * "http://creativecommons.org/licenses/xx-xx/xx/xx", where "xx" names a
   * license feature.
   */
  public void addUrlFeatures(NutchDocument doc, String urlString) {
    try {
      URL url = new URL(urlString);

      // tokenize the path of the url, breaking at slashes and dashes
      StringTokenizer names = new StringTokenizer(url.getPath(), "/-");

      if (names.hasMoreTokens())
        names.nextToken(); // throw away "licenses"

      // add a feature per component after "licenses"
      while (names.hasMoreTokens()) {
        String feature = names.nextToken();
        addFeature(doc, feature);
      }
    } catch (MalformedURLException e) {
      if (LOG.isWarnEnabled()) {
        LOG.warn("CC: failed to parse url: " + urlString + " : " + e);
      }
    }
  }

  private void addFeature(NutchDocument doc, String feature) {
    doc.add(FIELD, feature);
  }

  public void setConf(Configuration conf) {
    this.conf = conf;
  }

  public Configuration getConf() {
    return this.conf;
  }

  @Override
  public Collection<Field> getFields() {
    return FIELDS;
  }

  @Override
  public NutchDocument filter(NutchDocument doc, String url, WebPage page)
      throws IndexingException {

    ByteBuffer blicense = page.getMetadata().get(
        new Utf8(CreativeCommons.LICENSE_URL));
    if (blicense != null) {
      String licenseUrl = Bytes.toString(blicense);
      if (LOG.isInfoEnabled()) {
        LOG.info("CC: indexing " + licenseUrl + " for: " + url.toString());
      }

      // add the entire license as cc:license=xxx
      addFeature(doc, "license=" + licenseUrl);

      // index license attributes extracted of the license url
      addUrlFeatures(doc, licenseUrl);
    }

    // index the license location as cc:meta=xxx
    ByteBuffer blicenseloc = page.getMetadata().get(
        new Utf8(CreativeCommons.LICENSE_LOCATION));
    if (blicenseloc != null) {
      String licenseLocation = Bytes.toString(blicenseloc);
      addFeature(doc, "meta=" + licenseLocation);
    }

    // index the work type cc:type=xxx
    ByteBuffer bworkType = page.getMetadata().get(
        new Utf8(CreativeCommons.WORK_TYPE));
    if (bworkType != null) {
      String workType = Bytes.toString(bworkType);
      addFeature(doc, workType);
    }

    return doc;
  }

}