code: public Document outputJDom(final WireFeed feed) throws IllegalArgumentException, FeedException {
          final String type = feed.getFeedType();
          final WireFeedGenerator generator = getFeedGenerators().getGenerator(type);
          if (generator == null) {
              throw new IllegalArgumentException("Invalid feed type [" + type + "]");
          }
  
          if (!generator.getType().equals(type)) {
              throw new IllegalArgumentException("WireFeedOutput type[" + type + "] and WireFeed type [" + type + "] don't match");
          }
          return generator.generate(feed);
      }
docs: Creates a JDOM document for the given WireFeed.
  <p>
  This method does not use the feed encoding property.
  <p>
  NOTE: All other output methods delegate to this method.
  <p>
  
  @param feed Abstract feed to create JDOM document from. The type of the WireFeed must match
  the type given to the FeedOuptut constructor.
  @return the JDOM document for the given WireFeed.
  @throws IllegalArgumentException thrown if the feed type of the WireFeedOutput and WireFeed
  don't match.
  @throws FeedException thrown if the JDOM document for the feed could not be created.