AutomatonURLFilter.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.urlfilter.automaton;

// JDK imports
import java.io.Reader;
import java.io.IOException;
import java.io.StringReader;
import java.util.regex.PatternSyntaxException;

// Hadoop imports
import org.apache.hadoop.conf.Configuration;

// Automaton imports
import dk.brics.automaton.RegExp;
import dk.brics.automaton.RunAutomaton;
import org.apache.nutch.net.*;
import org.apache.nutch.urlfilter.api.RegexRule;
import org.apache.nutch.urlfilter.api.RegexURLFilterBase;


/**
 * RegexURLFilterBase implementation based on the
 * <a href="http://www.brics.dk/automaton/">dk.brics.automaton</a>
 * Finite-State Automata for Java<sup>TM</sup>.
 *
 * @author Jérôme Charron
 * @see <a href="http://www.brics.dk/automaton/">dk.brics.automaton</a>
 */
public class AutomatonURLFilter extends RegexURLFilterBase {
  public static final String URLFILTER_AUTOMATON_FILE = "urlfilter.automaton.file";
  public static final String URLFILTER_AUTOMATON_RULES = "urlfilter.automaton.rules";

  public AutomatonURLFilter() {
    super();
  }

  public AutomatonURLFilter(String filename)
    throws IOException, PatternSyntaxException {
    super(filename);
  }

  AutomatonURLFilter(Reader reader)
    throws IOException, IllegalArgumentException {
    super(reader);
  }

  
  /* ----------------------------------- *
   * <implementation:RegexURLFilterBase> *
   * ----------------------------------- */
  
  /**
   * Rules specified as a config property will override rules specified
   * as a config file.
   */
  protected Reader getRulesReader(Configuration conf) throws IOException {
    String stringRules = conf.get(URLFILTER_AUTOMATON_RULES);
    if (stringRules != null) {
      return new StringReader(stringRules);
    }
    String fileRules = conf.get(URLFILTER_AUTOMATON_FILE);
    return conf.getConfResourceAsReader(fileRules);
  }

  // Inherited Javadoc
  protected RegexRule createRule(boolean sign, String regex) {
    return new Rule(sign, regex);
  }
  
  /* ------------------------------------ *
   * </implementation:RegexURLFilterBase> *
   * ------------------------------------ */

  
  public static void main(String args[]) throws IOException {
    main(new AutomatonURLFilter(), args);
  }


  private class Rule extends RegexRule {
    
    private RunAutomaton automaton;
    
    Rule(boolean sign, String regex) {
      super(sign, regex);
      automaton = new RunAutomaton(new RegExp(regex, RegExp.ALL).toAutomaton());
    }

    protected boolean match(String url) {
      return automaton.run(url);
    }
  }
  
}