AtomFeedParser.java

/* LanguageTool, a natural language style checker
 * Copyright (C) 2013 Daniel Naber (http://www.danielnaber.de)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */
package org.languagetool.dev.wikipedia.atom;

import javax.xml.datatype.DatatypeFactory;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.XMLEvent;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

/**
 * Parse the Atom feed of Wikipedia's latest changes.
 * @since 2.4
 */
class AtomFeedParser {

  List<AtomFeedItem> getAtomFeedItems(InputStream xml) throws XMLStreamException {
    String id = null;
    String title = null;
    Date date = null;
    XMLInputFactory inputFactory = XMLInputFactory.newInstance();
    XMLEventReader eventReader = inputFactory.createXMLEventReader(xml);
    try {
      List<AtomFeedItem> items = new ArrayList<>();
      while (eventReader.hasNext()) {
        XMLEvent event = eventReader.nextEvent();
        if (event.isStartElement()) {
          String localPart = event.asStartElement().getName().getLocalPart();
          switch (localPart) {
            case "id":
              id = getCharacterData(eventReader);
              break;
            case "title":
              title = getCharacterData(eventReader);
              break;
            case "updated":
              String dateString = getCharacterData(eventReader);
              try {
                // e.g. 2013-12-03T09:48:29Z - got this from http://stackoverflow.com/questions/6038136,
                // with SimpleDateParser the hour is off by one:
                date = DatatypeFactory.newInstance().newXMLGregorianCalendar(dateString).toGregorianCalendar().getTime();
              } catch (Exception e) {
                throw new RuntimeException("Could not parse date string '" + dateString + "'", e);
              }
              break;
            case "summary":
              if (id == null || title == null || date == null) {
                throw new RuntimeException("id, title and/or date is null: id=" + id + ", title=" + title + ", date=" + date);
              }
              items.add(new AtomFeedItem(id, title, getCharacterData(eventReader), date));
              id = null;
              title = null;
              date = null;
              break;
          }
        }
      }
      return items;
    } finally {
      eventReader.close();
    }
  }

  private String getCharacterData(XMLEventReader eventReader) throws XMLStreamException {
    XMLEvent event = eventReader.nextEvent();
    StringBuilder sb = new StringBuilder();
    while (event.isCharacters()) {
      sb.append(event.asCharacters().getData());
      event = eventReader.nextEvent();
    }
    return sb.toString();
  }

}