Android Open Source - SimpleReader R S S Handler

From Project

Back to project page SimpleReader.
License

The source code is released under:
Apache License
If you think the Android project SimpleReader listed in this page is inappropriate, such as containing malicious code/tools or violating the copyright, please email info at java2s dot com, thanks.
Java Source Code

/*
 * Copyright (C) 2010 A. Horn//  ww w.j a  va2s .  c  o m
 *
 * Licensed 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 com.dreamteam.app.rss;

/**
 * Internal SAX handler to efficiently parse RSS feeds. Only a single thread
 * must use this SAX handler.
 * 
 * @author Mr Horn
 */
class RSSHandler extends org.xml.sax.helpers.DefaultHandler {

  /**
   * Constant for XML element name which identifies RSS items.
   */
  private static final String RSS_ITEM = "item";

  /**
   * Constant symbol table to ensure efficient treatment of handler states.
   */
  private final java.util.Map<String, Setter> setters;

  /**
   * Reference is never {@code null}. Visibility must be package-private to
   * ensure efficiency of inner classes.
   */
  final RSSFeed feed = new RSSFeed();

  /**
   * Reference is {@code null} unless started to parse &lt;item&gt; element.
   * Visibility must be package-private to ensure efficiency of inner classes.
   */
  RSSItem item;

  /**
   * If not {@code null}, then buffer the characters inside an XML text element.
   */
  private StringBuilder buffer;

  /**
   * Dispatcher to set either {@link #feed} or {@link #item} fields.
   */
  private Setter setter;

  /**
   * Interface to store information about RSS elements.
   */
  private static interface Setter {}

  /**
   * Closure to change fields in POJOs which store RSS content.
   */
  private static interface ContentSetter extends Setter {

    /**
     * Set the field of an object which represents an RSS element.
     */
    void set(String value);

  }

  /**
   * Closure to change fields in POJOs which store information
   * about RSS elements which have only attributes.
   */
  private static interface AttributeSetter extends Setter {

    /**
     * Set the XML attributes.
     */
    void set(org.xml.sax.Attributes attributes);

  }

  /**
   * Setter for RSS &lt;title&gt; elements inside a &lt;channel&gt; or an
   * &lt;item&gt; element. The title of the RSS feed is set only if
   * {@link #item} is {@code null}. Otherwise, the title of the RSS
   * {@link #item} is set.
   */
  private final Setter SET_TITLE = new ContentSetter() {
    @Override
    public void set(String title) {
      if (item == null) {
        feed.setTitle(title);
      } else {
        item.setTitle(title);
      }
    }
  };

  /**
   * Setter for RSS &lt;description&gt; elements inside a &lt;channel&gt; or an
   * &lt;item&gt; element. The title of the RSS feed is set only if
   * {@link #item} is {@code null}. Otherwise, the title of the RSS
   * {@link #item} is set.
   */
  private final Setter SET_DESCRIPTION = new ContentSetter() {
    @Override
    public void set(String description) {
      if (item == null) {
        feed.setDescription(description);
      } else {
        item.setDescription(description);
      }
    }
  };
  
  /**
   * Setter for an RSS &lt;content:encoded&gt; element inside an &lt;item&gt;
   * element.
   */
  private final Setter SET_CONTENT = new ContentSetter() {
    @Override
    public void set(String content) {
      if (item != null) {
        item.setContent(content);
      }
    }
  };

  /**
   * Setter for RSS &lt;link&gt; elements inside a &lt;channel&gt; or an
   * &lt;item&gt; element. The title of the RSS feed is set only if
   * {@link #item} is {@code null}. Otherwise, the title of the RSS
   * {@link #item} is set.
   */
  private final Setter SET_LINK = new ContentSetter() {
    @Override
    public void set(String link) {
      final android.net.Uri uri = android.net.Uri.parse(link);
      if (item == null) {
        feed.setLink(uri);
      } else {
        item.setLink(uri);
      }
    }
  };

  /**
   * Setter for RSS &lt;pubDate&gt; elements inside a &lt;channel&gt; or an
   * &lt;item&gt; element. The title of the RSS feed is set only if
   * {@link #item} is {@code null}. Otherwise, the title of the RSS
   * {@link #item} is set.
   */
  private final Setter SET_PUBDATE = new ContentSetter() {
    @Override
    public void set(String pubDate) {
      final java.util.Date date = Dates.parseRfc822(pubDate);
      if (item == null) {
        feed.setPubDate(date);
      } else {
        item.setPubDate(date);
      }
    }
  };

  /**
   * Setter for RSS &lt;lastBuildDate&gt; elements inside a &lt;channel&gt;.
   */
  private final Setter SET_LAST_BUILE_DATE = new ContentSetter() {
    @Override
    public void set(String pubDate) {
      final java.util.Date date = Dates.parseRfc822(pubDate);
      if (item == null) {
        feed.setLastBuildDate(date);
      } else {
        // Ignore invalid elements which are inside item elements.
      }
    }
  };

  /**
   * Setter for RSS &lt;ttl&gt; elements inside a &lt;channel&gt;.
   */
  private final Setter SET_TTL = new ContentSetter() {
    @Override
    public void set(String ttl) {
      final Integer value = Integers.parseInteger(ttl);
      if (item == null) {
        feed.setTTL(value);
      } else {
        // Ignore invalid elements which are inside item elements.
      }
    }
  };

  /**
   * Setter for one or multiple RSS &lt;category&gt; elements inside a
   * &lt;channel&gt; or an &lt;item&gt; element. The title of the RSS feed is
   * set only if {@link #item} is {@code null}. Otherwise, the title of the RSS
   * {@link #item} is set.
   */
  private final Setter ADD_CATEGORY = new ContentSetter() {

    @Override
    public void set(String category) {
      if (item == null) {
        feed.addCategory(category);
      } else {
        item.addCategory(category);
      }
    }
  };

  /**
   * Setter for one or multiple RSS &lt;media:thumbnail&gt; elements inside an
   * &lt;item&gt; element. The thumbnail element has only attributes. Both its
   * height and width are optional. Invalid elements are ignored.
   */
  private final Setter ADD_MEDIA_THUMBNAIL = new AttributeSetter() {

    private static final String MEDIA_THUMBNAIL_HEIGHT = "height";
    private static final String MEDIA_THUMBNAIL_WIDTH = "width";
    private static final String MEDIA_THUMBNAIL_URL = "url";
    private static final int DEFAULT_DIMENSION = -1;

    @Override
    public void set(org.xml.sax.Attributes attributes) {
      if (item == null) {
        // ignore invalid media:thumbnail elements which are not inside item
        // elements
        return;
      }

      final int height = MediaAttributes.intValue(attributes, MEDIA_THUMBNAIL_HEIGHT, DEFAULT_DIMENSION);
      final int width = MediaAttributes.intValue(attributes, MEDIA_THUMBNAIL_WIDTH, DEFAULT_DIMENSION);
      final String url = MediaAttributes.stringValue(attributes, MEDIA_THUMBNAIL_URL);

      if (url == null) {
        // ignore invalid media:thumbnail elements which have no URL.
        return;
      }

      item.addThumbnail(new MediaThumbnail(android.net.Uri.parse(url), height, width));
    }

  };

  /**
   * Setter for RSS &lt;enclosure&gt; elements inside an &lt;item&gt; element.
   */
  private final Setter SET_ENCLOSURE = new AttributeSetter() {

    private static final String URL = "url";
    private static final String LENGTH = "length";
    private static final String MIMETYPE = "type";

    @Override
    public void set(org.xml.sax.Attributes attributes) {
      if (item == null) {
        // Ignore invalid elements which are not inside item elements.
        return;
      }

      final String url = MediaAttributes.stringValue(attributes, URL);
      final Integer length = MediaAttributes.intValue(attributes, LENGTH);
      final String mimeType = MediaAttributes.stringValue(attributes,
          MIMETYPE);

      if (url == null || length == null || mimeType == null) {
        // Ignore invalid elements.
        return;
      }

      MediaEnclosure enclosure = new MediaEnclosure(
          android.net.Uri.parse(url), length, mimeType);
      item.setEnclosure(enclosure);
    }
  };

  /**
   * Use configuration to optimize initial capacities of collections
   */
  private final RSSConfig config;

  /**
   * Instantiate a SAX handler which can parse a subset of RSS 2.0 feeds.
   * 
   * @param config configuration for the initial capacities of collections
   */
  RSSHandler(RSSConfig config) {
    this.config = config;

    // initialize dispatchers to manage the state of the SAX handler
    setters = new java.util.HashMap<String, Setter>(/* 2^3 */16);
    setters.put("title", SET_TITLE);
    setters.put("description", SET_DESCRIPTION);
    setters.put("content:encoded", SET_CONTENT);
    setters.put("link", SET_LINK);
    setters.put("category", ADD_CATEGORY);
    setters.put("pubDate", SET_PUBDATE);
    setters.put("media:thumbnail", ADD_MEDIA_THUMBNAIL);
    setters.put("lastBuildDate", SET_LAST_BUILE_DATE);
    setters.put("ttl", SET_TTL);
    setters.put("enclosure", SET_ENCLOSURE);
  }

  /**
   * Returns the RSS feed after this SAX handler has processed the XML document.
   */
  RSSFeed feed() {
    return feed;
  }

  /**
   * Identify the appropriate dispatcher which should be used to store XML data
   * in a POJO. Unsupported RSS 2.0 elements are currently ignored.
   */
  @Override
  public void startElement(String nsURI, String localName, String qname,
      org.xml.sax.Attributes attributes) {
    // Lookup dispatcher in hash table
    setter = setters.get(qname);
    if (setter == null) {
      if (RSS_ITEM.equals(qname)) {
        item = new RSSItem(config.categoryAvg, config.thumbnailAvg);
      }
    } else if (setter instanceof AttributeSetter) {
      ((AttributeSetter) setter).set(attributes);
    } else {
      // Buffer supported RSS content data
      buffer = new StringBuilder();
    }
  }

  @Override
  public void endElement(String nsURI, String localName, String qname) {
    if (isBuffering()) {
      // set field of an RSS feed or RSS item
      ((ContentSetter) setter).set(buffer.toString());

      // clear buffer
      buffer = null;
    } else if (RSS_ITEM.equals(qname)) {
      feed.addItem(item);

      // (re)enter <channel> scope
      item = null;
    }
  }

  @Override
  public void characters(char ch[], int start, int length) {
    if (isBuffering()) {
      buffer.append(ch, start, length);
    }
  }

  /**
   * Determines if the SAX parser is ready to receive data inside an XML element
   * such as &lt;title&gt; or &lt;description&gt;.
   * 
   * @return boolean {@code true} if the SAX handler parses data inside an XML
   *         element, {@code false} otherwise
   */
  boolean isBuffering() {
    return buffer != null && setter != null;
  }

}
Java Source Code List
