Creating an RSS Feed (part 2)Tag(s): XML


To create a RSS feed using external librairies, see this HowTo

RSS Feed are XML files. They are easy to create, you can do it yourself.

First we need a bean representing the header

package com.rgagnon.howto.rss;

public class RSSHeader {
  private String title = "";
  private String description = "";
  private String link = "";
  private String language = "";
  private String copyright = "";
  private String author = "";
  private String guid = "";
  private String pubdate ="";
  
  public String getTitle() {
    return title;
  }
  public void setTitle(String title) {
    this.title = title;
  }
  public String getDescription() {
    return description;
  }
  public void setDescription(String description) {
    this.description = description;
  }
  public String getLink() {
    return link;
  }
  public void setLink(String link) {
    this.link = link;
  }
  public String getLanguage() {
    return language;
  }
  public void setLanguage(String language) {
    this.language = language;
  }
  public String getCopyright() {
    return copyright;
  }
  public void setCopyright(String copyright) {
    this.copyright = copyright;
  }
  public String getAuthor() {
    return author;
  }
  public void setAuthor(String author) {
    this.author = author;
  }
  public String getGuid() {
    return guid;
  }
  public void setGuid(String guid) {
    this.guid = guid;
  }
  public String getPubDate() {
    return pubdate;
  }
  public void setPubDate(String pubdate) {
    this.pubdate = pubdate;
  }
}

Next we need a bean representing an entry

package com.rgagnon.howto.rss;

public class RSSEntry {
  private String title = "";
  private String link = "";
  private String description = "";
  private String language = "";
  private String copyright = "";
  private String pubDate = "";
  private String guid = "";

  public String getTitle() {
    return title;
  }
  public void setTitle(String title) {
    this.title = title;
  }
  public String getLink() {
    return link;
  }
  public void setLink(String link) {
    this.link = link;
  }
  public String getDescription() {
    return description;
  }
  public void setDescription(String description) {
    this.description = description;
  }
  public String getLanguage() {
    return language;
  }
  public void setLanguage(String language) {
    this.language = language;
  }
  public String getCopyright() {
    return copyright;
  }
  public void setCopyright(String copyright) {
    this.copyright = copyright;
  }
  public String getPubDate() {
    return pubDate;
  }
  public void setPubDate(String pubDate) {
    this.pubDate = pubDate;
  }
  public String getGuid() {
    return guid;
  }
  public void setGuid(String guid) {
    this.guid = guid;
  }
}

Then a class to contain the header plus the entries

package com.rgagnon.howto.rss;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.List;
import java.util.Locale;

public class RSSFeed {
  private RSSHeader header;
  private List<RSSEntry> entries;
  
  public void setHeader(RSSHeader header){
    this.header = header;
  }
  
  public void setEntries(List entries){
    this.entries = entries;
  }

  public RSSHeader getHeader() {
    return header;
  }
  
  public List<RSSEntry> getEntries() {
    return entries;
  }
  
  public static String formatDate(Calendar cal) {
    SimpleDateFormat sdf = new SimpleDateFormat(
        "EEE, dd MMM yyyy HH:mm:ss Z", Locale.US);
    return sdf.format(cal.getTime());
  }
}

A class to build the XML

package com.rgagnon.howto.rss;

import java.io.FileOutputStream;
import java.util.Iterator;

import javax.xml.stream.XMLEventFactory;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartDocument;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

public class RSSWriter {
  private static String XML_BLOCK = "\n";
  private static String XML_INDENT = "\t";
  
  public static void write(RSSFeed rssfeed, String xmlfile) throws Exception {
    XMLOutputFactory output = XMLOutputFactory.newInstance();
    XMLEventWriter writer = output.createXMLEventWriter
      (new FileOutputStream(xmlfile));
    XMLEventFactory eventFactory = XMLEventFactory.newInstance();
    XMLEvent endSection = eventFactory.createDTD(XML_BLOCK);

    StartDocument startDocument = eventFactory.createStartDocument();
    writer.add(startDocument);
    writer.add(endSection);
    StartElement rssStart = eventFactory.createStartElement("", "", "rss");
    writer.add(rssStart);
    writer.add(eventFactory.createAttribute("version", "2.0"));
    writer.add(endSection);

    writer.add(eventFactory.createStartElement("", "", "channel"));
    writer.add(endSection);

    RSSHeader header = rssfeed.getHeader();
    createNode(writer, "title", header.getTitle());
    createNode(writer, "link", header.getLink());
    createNode(writer, "description", header.getDescription());
    createNode(writer, "language", header.getLanguage());
    createNode(writer, "copyright", header.getCopyright());
    createNode(writer, "pubDate", header.getPubDate());
    Iterator<RSSEntry> iterator = rssfeed.getEntries().iterator();
    while (iterator.hasNext()) {
      RSSEntry entry = iterator.next();
      writer.add(eventFactory.createStartElement("", "", "item"));
      writer.add(endSection);
      createNode(writer, "title", entry.getTitle());
      createNode(writer, "description", entry.getDescription());
      createNode(writer, "link", entry.getLink());
      createNode(writer, "guid", entry.getGuid());
      createNode(writer, "pubDate", entry.getPubDate());
      writer.add(eventFactory.createEndElement("", "", "item"));
      writer.add(endSection);
    }

    writer.add(endSection);
    writer.add(eventFactory.createEndElement("", "", "channel"));
    writer.add(endSection);
    writer.add(eventFactory.createEndElement("", "", "rss"));

    writer.add(endSection);
    writer.add(eventFactory.createEndDocument());
    writer.close();
  }

  private static void createNode
    (XMLEventWriter eventWriter, String name, String value) 
     throws XMLStreamException {
    XMLEventFactory eventFactory = XMLEventFactory.newInstance();
    XMLEvent endSection = eventFactory.createDTD(XML_BLOCK);
    XMLEvent tabSection = eventFactory.createDTD(XML_INDENT);

    StartElement sElement = eventFactory.createStartElement("", "", name);
    eventWriter.add(tabSection);
    eventWriter.add(sElement);

    Characters characters = eventFactory.createCharacters(value);
    eventWriter.add(characters);

    EndElement eElement = eventFactory.createEndElement("", "", name);
    eventWriter.add(eElement);
    eventWriter.add(endSection);
  }
}

Finally, an example on how to generate a file

package com.rgagnon.howto.rss;

import java.util.ArrayList;
import java.util.Calendar;

public class TestRSSWriter {
    private static String RSSFEED = "c:/temp/feed.xml";
    
    public static void main(String[] args) {
      System.out.println("Creation RSS Feed (" + RSSFEED + ")");
      RSSFeed feed = new RSSFeed();

      RSSHeader header = new RSSHeader();
      header.setCopyright("Copyright by Real Gagnon");
      header.setTitle("Real's HowTo");
      header.setDescription("Useful code snippets for Java");
      header.setLanguage("en");
      header.setLink("http://www.rgagnon.com");
      header.setPubDate(RSSFeed.formatDate(Calendar.getInstance()));

      feed.setHeader(header);
      
      ArrayList<RSSEntry> entries = new ArrayList<RSSEntry>();
      RSSEntry entry = new RSSEntry();
      entry.setTitle("The PDF are updated");
      entry.setDescription("Java (756 pages), Powerbuilder (197), Javascript (99) and VBS (32)");
      entry.setGuid("http://64.18.163.122/rgagnon/download/index.htm");
      entry.setLink("http://64.18.163.122/rgagnon/download/index.htm");
      entry.setPubDate(RSSFeed.formatDate(Calendar.getInstance()));
      entries.add(entry);
      
      entry = new RSSEntry();
      entry.setTitle("Java : Display a TIF");
      entry.setDescription("Using JAI, how to display a TIF file");
      entry.setGuid("http://www.rgagnon.com/javadetails/java-0605.html");
      entry.setLink("http://www.rgagnon.com/javadetails/java-0605.html");
      entry.setPubDate(RSSFeed.formatDate(Calendar.getInstance()));
      entries.add(entry);
      
      feed.setEntries(entries);
      
      try {
        RSSWriter.write(feed, TestRSSWriter.RSSFEED);
      } 
      catch (Exception e) {
        e.printStackTrace();
      }
      System.out.println("Done.");
    }
}

The result is

<?xml version="1.0"?>
<rss version="2.0">
<channel>
    <title>Real's HowTo</title>
    <link>http://www.rgagnon.com</link>
    <description>Useful code snippets for Java</description>
    <language>en</language>
    <copyright>Copyright by Real Gagnon</copyright>
    <pubDate>Mon, 23 Jun 2008 11:15:31 -0400</pubDate>
<item>
    <title>The PDF are updated</title>
    <description>Java (756 pages), Powerbuilder (197), Javascript (99) and VBS (32)</description>
    <link>http://64.18.163.122/rgagnon/download/index.htm</link>
    <guid>http://64.18.163.122/rgagnon/download/index.htm</guid>
    <pubDate>Mon, 23 Jun 2008 11:15:31 -0400</pubDate>
</item>
<item>
    <title>Java : Display a TIF</title>
    <description>Using JAI, how to display a TIF file</description>
    <link>http://www.rgagnon.com/javadetails/java-0605.html</link>
    <guid>http://www.rgagnon.com/javadetails/java-0605.html</guid>
    <pubDate>Mon, 23 Jun 2008 11:15:31 -0400</pubDate>
</item>

</channel>
</rss>


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