Java HTML/XML - 如何使用DOM创建RSS阅读器

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

public class Main {
  public static void main(String[] args) throws Exception {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document doc = builder.parse(new File("testrss.xml"));

    Element root = doc.getDocumentElement();
    if (!root.getTagName().equalsIgnoreCase("rss")) {
      throw new IOException("Invalid RSS document");
    }
    List<RSSChannel> channels = readChannels(root.getChildNodes());
    for (RSSChannel channel : channels) {
      System.out.println("Channel: ");
      System.out.println("    title: " + channel.getTitle());
      System.out.println("    link: " + channel.getLink());
      System.out.println("    description: " + channel.getDescription());
      for (RSSItem item : channel.getItems()) {
        System.out.println("    Item: ");
        System.out.println("        title: " + item.getTitle());
        System.out.println("        link: " + item.getLink());
        System.out.println("        description: " + item.getDescription());
        System.out.println("        pubDate: " + item.getPubDate());
        System.out.println("        guid: " + item.getGuid());
      }
    }
  }
  private static List<RSSChannel> readChannels(NodeList nodes) {
    List<RSSChannel> result = new ArrayList<RSSChannel>();
    for (int i = 0; i < nodes.getLength(); ++i) {
      Node node = nodes.item(i);
      if (node instanceof Element) {
        Element elem = (Element) node;
        if (elem.getTagName().equalsIgnoreCase("channel")) {
          result.add(readChannel(elem.getChildNodes()));
        }
      }
    }
    return result;
  }

  private static RSSChannel readChannel(NodeList nodes) {
    RSSChannel channel = new RSSChannel();
    for (int i = 0; i < nodes.getLength(); ++i) {
      Node node = nodes.item(i);
      if (node instanceof Element) {
        Element elem = (Element) node;
        if (elem.getTagName().equalsIgnoreCase("title")) {
          channel.setTitle(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("link")) {
          channel.setLink(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("description")) {
          channel.setDescription(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("item")) {
          channel.addItem(readItem(elem.getChildNodes()));
        }
      }
    }
    return channel;
  }

  private static RSSItem readItem(NodeList nodes) {
    RSSItem item = new RSSItem();
    for (int i = 0; i < nodes.getLength(); ++i) {
      Node node = nodes.item(i);
      if (node instanceof Element) {
        Element elem = (Element) node;
        if (elem.getTagName().equalsIgnoreCase("title")) {
          item.setTitle(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("link")) {
          item.setLink(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("description")) {
          item.setDescription(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("pubDate")) {
          item.setPubDate(getText(elem));
        } else if (elem.getTagName().equalsIgnoreCase("guid")) {
          item.setGuid(getText(elem));
        }
      }
    }
    return item;
  }

  private static String getText(Element elm) {
    Node node = elm.getFirstChild();
    if (!(node instanceof Text)) {
      return null;
    }
    Text text = (Text) node;
    return text.getData().trim();
  }
}

class RSSChannel {

  public RSSChannel() {
    this.title = "";
    this.link = "";
    this.description = "";
  }

  public RSSChannel(String title, String link, String description) {

    this.title = title;
    this.link = link;
    this.description = description;
  }

  public void setTitle(String title) {
    this.title = title;
  }

  public void setLink(String link) {
    this.link = link;
  }

  public void setDescription(String description) {
    this.description = description;
  }

  public String getTitle() {
    return title;
  }

  public String getLink() {
    return link;
  }

  public String getDescription() {
    return description;
  }

  public List<RSSItem> getItems() {
    return new ArrayList<RSSItem>(items);
  }

  public void addItem(RSSItem item) {
    items.add(item);
  }

  private String title;
  private String link;
  private String description;
  private List<RSSItem> items = new ArrayList<RSSItem>();
}

class RSSItem {

  public RSSItem() {

    this.title = "";
    this.link = "";
    this.description = "";
    this.pubDate = "";
    this.guid = "";
  }

  public RSSItem(String title, String link, String description, String item,
      String pubDate, String guid) {

    this.title = title;
    this.link = link;
    this.description = description;
    this.pubDate = pubDate;
    this.guid = guid;
  }

  public void setTitle(String title) {
    this.title = title;
  }

  public void setLink(String link) {
    this.link = link;
  }

  public void setDescription(String description) {
    this.description = description;
  }

  public void setPubDate(String pubDate) {
    this.pubDate = pubDate;
  }

  public void setGuid(String guid) {
    this.guid = guid;
  }

  public String getTitle() {
    return title;
  }

  public String getDescription() {
    return description;
  }

  public String getGuid() {
    return guid;
  }

  public String getLink() {
    return link;
  }

  public String getPubDate() {
    return pubDate;
  }

  private String title;
  private String link;
  private String description;
  private String pubDate;
  private String guid;
}