<pre class="brush: xml;highlight:[7,11]">
&lt;?xml version="1.0" encoding="UTF-8"?>
&lt;rss xmlns:atom="http://www.w3.org/2005/Atom" version="2.0">
 &lt;channel>
 &lt;!-- title, link, description are required -->
 &lt;title>Primo's code blogs feeds&lt;/title>
 &lt;description>Feeds from Kahimyang Projects Primo's code blogs&lt;/description>
 &lt;link>https://kahimyang.com/kauswagan/RssFeeds.xml?type=howto&lt;/link>
 &lt;language>en&lt;/language>

 &lt;!-- Only for feed reader interoperability -->
 &lt;atom:link rel="self" href="https://kahimyang.com/kauswagan/RssFeeds.xml?type=howto" 
 type="application/rss+xml" />

 &lt;!-- Contents of the feed -->
 &lt;item>
 &lt;title>
 Title of the story item.
 &lt;/title>
 &lt;link>
 URL that points to the full content.
 &lt;/link>
 &lt;description>
 &lt;![CDATA[
 Description of the item. In the case of a blog or 
 news item, this can be the synopsis. 
 ]]>
 &lt;/description>
 &lt;guid>
 unique_id_of_the_feed_item
 &lt;/guid>
 
 &lt;!-- Required format. Publication date -->
 &lt;pubDate>Fri, 16 Sep 2011 14:31:01 EDT&lt;/pubDate>

 &lt;/item>

 &lt;!-- more items -->

 &lt;/channel>
&lt;/rss>
</pre>



The sample feed above was generated based on the recommendation of the <a href="http://feed2.w3.org/" class="news_link" target="_blank" title="Feed validator">Feed Validator Service from w3.org</a>. 


Elements &lt;link /> and &lt;atom:link /> in lines 7 and 11 should point to the URL of the feed. Sub-element &lt;link /> of &lt;item /> points to the URL of the item itself.&nbsp;&nbsp;Date and time values should conform to <a href="http://asg.web.cmu.edu/rfc/rfc822.html" target="_blank" class="news_link" title="RFC #822">RFC #822</a>.&nbsp;&nbsp;Wrapping the description with CDATA is required if the content has HTML formatting.


Here is the servlet that generated the above sample feed.&nbsp;&nbsp;Please refer to the inline comments for more information. In this servlet, 

items are drawn from a database. Please note that some lines were removed for clarity.



<pre class="brush: java;highlight:[30,77,112,113,114]">

package pname;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.jdom2.CDATA;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.Namespace;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;
import org.jsoup.Jsoup;
import org.jsoup.safety.Whitelist;

@WebServlet(name = "RssFeeds", urlPatterns = {"/RssFeeds.xml"})
public class RssFeeds extends HttpServlet {

 @Override
 protected void doGet (HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 
 response.setContentType("application/xml;charset=UTF-8");
 PrintWriter servlet = response.getWriter();
 
 try {
 // Create the root rss element 
 Element rssRoot = new Element("rss");


 // Required attribute
 rssRoot.setAttribute("version", "2.0");
 
 // Create the XML document
 Document feed = new Document();
 feed.setRootElement(rssRoot);
 
 Element channel = new Element("channel");
 
 rssRoot.addContent(channel);


 channel.addContent(new Element("title").
 addContent("Title of the Feed"));
 channel.addContent(new Element("description").
 addContent("Description of the entire feed"));
 
 final String url=
 "https://kahimyang.com/kauswagan/RssFeeds.xml?type=howto";
 
 channel.addContent(new Element ("link").addContent (url)); 
 channel.addContent(new Element("language").addContent("en"));


 // Create the atom namespace
 Namespace atom = 
 Namespace.getNamespace("atom","http://www.w3.org/2005/Atom");
 rssRoot.addNamespaceDeclaration(atom); 
 
 Element link = new Element ("link",atom); // atom:link
 link.setAttribute("rel","self").setAttribute("href",url).
 setAttribute("type","application/rss+xml");

 channel.addContent(link);
 
 addRssItems (channel); // the actual feeds
 
 // Write the document to the servlet response
 XMLOutputter output = new XMLOutputter();
 output.setFormat(Format.getPrettyFormat().setEncoding("UTF-8"));
 output.output(feed, servlet);

 } 
 finally {
 servlet.flush();
 servlet.close();
 }
 }


 void addRssItems (Element channel) {

 // Build the query 
 StringBuilder q = new StringBuilder("select ...");

 try (
 // Change the way you connect to database.
 Connection conn = DatasourceConnection.getConnection();
 Statement stmt = conn.createStatement();
 ResultSet result = stmt.executeQuery(q.toString())) {


 while (result.next()) {

 Element item = new Element("item");
 item.addContent(new Element("title").
 addContent(result.getString(1)));

 // link to the item itself
 item.addContent(new Element("link").
 addContent(result.getString(2)));

 // This can be a sysnopsis
 // Strip off risky attributes from html tags
 String teaser=Jsoup.clean(result.getString(3),Whitelist.basic());
 item.addContent(new Element("description").
 addContent(new CDATA(teaser)));

 // Unique ID, usually this is the same as link 
 item.addContent(new Element("guid").addContent("the_unique_id"));
 
 // Required format
 SimpleDateFormat f = 
 new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz");
 item.addContent(new Element("pubDate").
 addContent(f.format(result.getTimestamp(4))));

 channel.addContent(item);

 }
 

 } catch (Exception e) {
 // return an empty channel
 }
 }


 @Override
 public String getServletInfo() {
 return "Short description";
 }
}
</pre>



Character encoding specified in lines 30 and 77 should match.&nbsp;&nbsp;Application type application/xml should also be used for some browsers to render the feed correctly. 



Additional library used in this servlet (line 112 above) is Jsoup. It can be downloaded here <a href="http://jsoup.org/" target="_blank" class="news_link" title="Jsoup">http://jsoup.org/</a>.



That's it Good Luck.

Generating XML RSS 2 feeds with JDOM 2 with a servlet