android-ibc-forum

RSSHandler.java (9343B)

---

 /*
  * Copyright (C) 2010 A. Horn
  *
  * 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 org.mcsoxford.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.setFullContent(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 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));
     }
 
   };
 
   /**
    * 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 */8);
     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);
   }
 
   /**
    * 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;
   }
 
 }