ParseResult.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.parse;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.Text;

/**
 * A utility class that stores result of a parse. Internally
 * a ParseResult stores <{@link Text}, {@link Parse}> pairs.
 * <p>Parsers may return multiple results, which correspond to parts
 * or other associated documents related to the original URL.</p>
 * <p>There will be usually one parse result that corresponds directly
 * to the original URL, and possibly many (or none) results that correspond
 * to derived URLs (or sub-URLs).
 */
public class ParseResult implements Iterable<Map.Entry<Text, Parse>> {
  private Map<Text, Parse> parseMap;
  private String originalUrl;
  
  public static final Log LOG = LogFactory.getLog(ParseResult.class);
  
  /**
   * Create a container for parse results.
   * @param originalUrl the original url from which all parse results
   * have been obtained.
   */
  public ParseResult(String originalUrl) {
    parseMap = new HashMap<Text, Parse>();
    this.originalUrl = originalUrl;
  }
  
  /**
   * Convenience method for obtaining {@link ParseResult} from a single
   * {@link Parse} output.
   * @param url canonical url
   * @param parse single parse output
   * @return result containing the single parse output
   */
  public static ParseResult createParseResult(String url, Parse parse) {
    ParseResult parseResult = new ParseResult(url);
    parseResult.put(new Text(url), new ParseText(parse.getText()), parse.getData());
    return parseResult;
  }
  
  /**
   * Checks whether the result is empty.
   * @return
   */
  public boolean isEmpty() {
    return parseMap.isEmpty();
  }
  
  /**
   * Return the number of parse outputs (both successful and failed)
   */
  public int size() {
    return parseMap.size();
  }
  
  /**
   * Retrieve a single parse output.
   * @param key sub-url under which the parse output is stored.
   * @return parse output corresponding to this sub-url, or null.
   */
  public Parse get(String key) {
    return get(new Text(key));
  }
  
  /**
   * Retrieve a single parse output.
   * @param key sub-url under which the parse output is stored.
   * @return parse output corresponding to this sub-url, or null.
   */
  public Parse get(Text key) {
    return parseMap.get(key);
  }
  
  /**
   * Store a result of parsing.
   * @param key URL or sub-url of this parse result
   * @param text plain text result
   * @param data corresponding parse metadata of this result
   */
  public void put(Text key, ParseText text, ParseData data) {
    put(key.toString(), text, data);
  }
  
  /**
   * Store a result of parsing.
   * @param key URL or sub-url of this parse result
   * @param text plain text result
   * @param data corresponding parse metadata of this result
   */
  public void put(String key, ParseText text, ParseData data) {
    parseMap.put(new Text(key), new ParseImpl(text, data, key.equals(originalUrl)));
  }

  /**
   * Iterate over all entries in the <url, Parse> map.
   */
  public Iterator<Entry<Text, Parse>> iterator() {
    return parseMap.entrySet().iterator();
  }
  
  /**
   * Remove all results where status is not successful (as determined
   * by {@link ParseStatus#isSuccess()}). Note that effects of this operation
   * cannot be reversed.
   */
  public void filter() {
    for(Iterator<Entry<Text, Parse>> i = iterator(); i.hasNext();) {
      Entry<Text, Parse> entry = i.next();
      if (!entry.getValue().getData().getStatus().isSuccess()) {
        LOG.warn(entry.getKey() + " is not parsed successfully, filtering");
        i.remove();
      }
    }
      
  }

  /**
   * A convenience method which returns true only if all parses are successful.
   * Parse success is determined by {@link ParseStatus#isSuccess()}
   */
  public boolean isSuccess() {
    for(Iterator<Entry<Text, Parse>> i = iterator(); i.hasNext();) {
      Entry<Text, Parse> entry = i.next();
      if (!entry.getValue().getData().getStatus().isSuccess()) {
        return false;
      }
    }
    return true;
  }
}