Rome v0.1 Tutorial, Using Rome to convert a syndication feed from one type to another

Software requirements: Synd J2SE 1.4+, Xerces 2.4.0, JDOM B10, Commons Codec 1.2 and Rome 0.1.

Rome represents syndication feeds (RSS and Atom) as instances of the com.sun.syndication.synd.SyndFeedI interface. The SyndFeedI interfaces and its properties follow the Java Bean patterns. The default implementations provided with Rome are all lightweight classes.

Rome includes parsers to process syndication feeds into SyndFeedI instances. The SyndInput class handles the parsers using the correct one based on the syndication feed being processed. The developer does not need to worry about selecting the right parser for a syndication feed, the SyndInput will take care of it by peeking at the syndication feed structure. All it takes to read a syndication feed using Rome are the following 2 lines of code:

SyndInput input = new SyndInput();
SyndFeedI feed = input.build(feedUrl.openStream());

The first line creates a SyndInput instance that will work with any syndication feed type (RSS and Atom versions). The second line instructs the SyndInput to read the syndication feed from the InputStream of a URL pointing to the feed. The SyndInput.build() method returns a SyndFeedI instance that can be easily processed.

Rome also includes generators to create syndication feeds out of SyndFeedI instances. The SyndOutput class does this generation. When creating a syndication feed output, the developer has to indicate the syndication feed type for the ouput, and the SyndOutput will use the right generator for it. The following two lines of code show how to create a syndication feed output from a SyndFeedI instance:

SyndOutput output = new SyndOutput(outputType);
output.output(feed,System.out);

The first line creates a SyndOutput instance that will produce syndication feeds of the type indicated by the outputType parameter. The outputType parameter can be any of the following values: rss_0.9, rss_0.91, rss_0.92, rss_0.93, rss_0.94, rss_1.0, rss_2.0 & atom_0.3. The second line writes the SyndFeedI as a syndication feed into the application's output.

Following is the full code for a Java application that reads a syndication feed and converts it to other syndication feed type, writing the converted feed to the application's output.

package com.sun.syndication.samples;

import java.net.URL;
import com.sun.syndication.feed.synd.SyndFeedI;
import com.sun.syndication.io.SyndInput;
import com.sun.syndication.io.SyndOutput;

public class FeedConverter {

    public static void main(String[] args) {
        boolean ok = false;
        if (args.length==2) {
            try {
                String outputType = args[0];

                URL feedUrl = new URL(args[1]);

                SyndInput input = new SyndInput(false);
                SyndFeedI feed = input.build(feedUrl.openStream());

                SyndOutput output = new SyndOutput(outputType);
                output.output(feed,System.out);

                ok = true;
            }
            catch (Exception ex) {
                System.out.println("ERROR: "+ex.getMessage());
            }
        }

        if (!ok) {
            System.out.println();
            System.out.println("FeedConverter converts between syndication feeds types.");
            System.out.println("The first parameter must be the feed type to convert to.");
            System.out.println(" [valid values are: rss_0.9, rss_0.91, rss_0.92, rss_0.93, ]");
            System.out.println(" [                  rss_0.94, rss_1.0, rss_2.0 & atom_0.3  ]");
            System.out.println("The second parameter must be the URL of the feed to convert.");
            System.out.println();
        }
    }

}