a cup of java

RSS (Really Simple Syndication)
RSS is way to publish frequently changing contents like blog posts, news updates, stock quotes & things like that. An RSS document, which is called a “feed,” “web feed,” or “channel,” contains either a summary of content from an associated web site or the full text. RSS formats are specified using XML, a generic specification for the creation of data formats.

I have attached a simple SAX parser for RSS. Please let me know if there is any flaw in the attached code. This code is provided for learning purpose with less focus on coding standards & it’s efficiency. You are free to use & modify it.

package subin.rnd.xml;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Properties;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.helpers.DefaultHandler;

public class RssParser extends DefaultHandler
{  
    private String        urlString;
    private RssFeed       rssFeed;
    private StringBuilder text;
    private Item          item;
    private boolean       imgStatus;
   
    public RssParser(String url)
    {
        this.urlString = url;
        this.text = new StringBuilder();
    }
   
    public void parse()
    {
        InputStream urlInputStream = null;
        SAXParserFactory spf = null;
        SAXParser sp = null;
       
        try
        {
            URL url = new URL(this.urlString);
            _setProxy(); // Set the proxy if needed
            urlInputStream = url.openConnection().getInputStream();           
            spf = SAXParserFactory.newInstance();
            if (spf != null)
            {
                sp = spf.newSAXParser();
                sp.parse(urlInputStream, this);
            }
        }

        /*
         * Exceptions need to be handled
         * MalformedURLException
         * ParserConfigurationException
         * IOException
         * SAXException
         */
       
        catch (Exception e)
        {
            System.out.println("Exception: " + e);
            e.printStackTrace();
        }
        finally
        {
            try
            {
                if (urlInputStream != null) urlInputStream.close();
            }
            catch (Exception e) {}
        }
    }

    public RssFeed getFeed()
    {
        return (this.rssFeed);
    }
   
    public void startElement(String uri, String localName, String qName,
            Attributes attributes)
    {
        if (qName.equalsIgnoreCase("channel"))
            this.rssFeed = new RssFeed();
        else if (qName.equalsIgnoreCase("item") && (this.rssFeed != null))
        {
            this.item = new Item();
            this.rssFeed.addItem(this.item);
        }
        else if (qName.equalsIgnoreCase("image") && (this.rssFeed != null))
            this.imgStatus = true;
    }
   
    public void endElement(String uri, String localName, String qName)
    {
        if (this.rssFeed == null)
            return;
       
        if (qName.equalsIgnoreCase("item"))
            this.item = null;
       
        else if (qName.equalsIgnoreCase("image"))
            this.imgStatus = false;
       
        else if (qName.equalsIgnoreCase("title"))
        {
            if (this.item != null) this.item.title = this.text.toString().trim();
            else if (this.imgStatus) this.rssFeed.imageTitle = this.text.toString().trim();
            else this.rssFeed.title = this.text.toString().trim();
        }       
       
        else if (qName.equalsIgnoreCase("link"))
        {
            if (this.item != null) this.item.link = this.text.toString().trim();
            else if (this.imgStatus) this.rssFeed.imageLink = this.text.toString().trim();
            else this.rssFeed.link = this.text.toString().trim();
        }       
       
        else if (qName.equalsIgnoreCase("description"))
        {
            if (this.item != null) this.item.description = this.text.toString().trim();
            else this.rssFeed.description = this.text.toString().trim();
        }
       
        else if (qName.equalsIgnoreCase("url") && this.imgStatus)
            this.rssFeed.imageUrl = this.text.toString().trim();
       
        else if (qName.equalsIgnoreCase("language"))
            this.rssFeed.language = this.text.toString().trim();
       
        else if (qName.equalsIgnoreCase("generator"))
            this.rssFeed.generator = this.text.toString().trim();
       
        else if (qName.equalsIgnoreCase("copyright"))
            this.rssFeed.copyright = this.text.toString().trim();
       
        else if (qName.equalsIgnoreCase("pubDate") && (this.item != null))
            this.item.pubDate = this.text.toString().trim();
       
        else if (qName.equalsIgnoreCase("category") && (this.item != null))
            this.rssFeed.addItem(this.text.toString().trim(), this.item);
       
        this.text.setLength(0);
    }
   
    public void characters(char[] ch, int start, int length)
    {
        this.text.append(ch, start, length);
    }
   
    public static void _setProxy()
    throws IOException
    {
        Properties sysProperties = System.getProperties();
        sysProperties.put("proxyHost", "<Proxy IP Address>");
        sysProperties.put("proxyPort", "<Proxy Port Number>");
        System.setProperties(sysProperties);
    }
  
    public static class RssFeed
    {
        public  String title;
        public  String description;
        public  String link;
        public  String language;
        public  String generator;
        public  String copyright;
        public  String imageUrl;
        public  String imageTitle;
        public  String imageLink;
       
        private ArrayList <Item> items;
        private HashMap <String, ArrayList <Item>> category;
       
        public void addItem(Item item)
        {
            if (this.items == null)
                this.items = new ArrayList<Item>();
            this.items.add(item);
        }
       
        public void addItem(String category, Item item)
        {
            if (this.category == null)
                this.category = new HashMap<String, ArrayList<Item>>();
            if (!this.category.containsKey(category))
                this.category.put(category, new ArrayList<Item>());
            this.category.get(category).add(item);
        }
    }
   
   
    public static class Item
    {
        public  String title;
        public  String description;
        public  String link;
        public  String pubDate;
       
        public String toString()
        {
            return (this.title + ": " + this.pubDate + "n" + this.description);
        }
    }
   
}

Using RssParser.java :

RssParser rp = new RssParser("<RSS Feed URL>");
rp.parse();
RssFeed feed = rp.getFeed();

// Listing all categories & the no. of elements in each category
if (feed.category != null)
{
 System.out.println("Category List: ");
 for (String category : feed.category.keySet())
 {
  System.out.println(category
    + ": "
    + ((ArrayList<Item>)feed.category.get(category)).size());
 }
}

// Listing all items in the feed
for (int i = 0; i < feed.items.size(); i++)
 System.out.println(feed.items.get(i).title);