MetaTagsQueryFilter.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.apache.nutch.searcher;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.PhraseQuery;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.BooleanClause.Occur;
import org.apache.nutch.plugin.Extension;
import org.apache.nutch.plugin.PluginDescriptor;
import org.apache.nutch.plugin.PluginRepository;
import org.apache.nutch.searcher.Query.Clause;
import org.apache.nutch.searcher.Query.Phrase;
import org.apache.nutch.searcher.Query.Term;

public class MetaTagsQueryFilter extends Configured implements QueryFilter {
  private static final Log LOG = LogFactory.getLog(MetaTagsQueryFilter.class);
  
  private Set<String> fields = new HashSet<String>();

  @Override
  public void setConf(Configuration conf) {
    super.setConf(conf);
    if (conf == null) {
      return;
    }
    // retrieve the plugin info and extract the list of fields
    PluginRepository pr = PluginRepository.get(conf);
    PluginDescriptor pd = pr.getPluginDescriptor("parse-metatags");
    Extension[] exts = pd.getExtensions();
    for (Extension e : exts) {
      String flds = e.getAttribute("fields");
      if (flds != null) {
        fields.addAll(Arrays.asList(flds.split("[\\s,]")));
      }
      flds = e.getAttribute("raw-fields");
      if (flds != null) {
        fields.addAll(Arrays.asList(flds.split("[\\s,]")));
      }
    }
    LOG.info("Query meta fields: " + fields.toString());
  }

  @Override
  public BooleanQuery filter(Query input, BooleanQuery translation)
          throws QueryException {
    
    for (Clause c : input.getClauses()) {
      if (!fields.contains(c.getField())) {
        continue;
      }
      org.apache.lucene.search.Query q;
      if (c.isPhrase()) {
        PhraseQuery pq = new PhraseQuery();
        Phrase p = c.getPhrase();
        for (Term t : p.getTerms()) {
          pq.add(new org.apache.lucene.index.Term(c.getField(), t.toString()));
        }
        q = pq;
      } else {
        Term t = c.getTerm();
        q = new TermQuery(new org.apache.lucene.index.Term(c.getField(), t.toString()));
      }
      translation.add(q, c.isRequired() ? Occur.MUST : c.isProhibited() ? Occur.MUST_NOT : Occur.SHOULD);
    }
    return translation;
  }

}