Parsing XML, should I use SAX or DOM?

[Chris Stewart]

I'm trying to parse some RSS feeds for my website, and I'm not really sure where to start. Can anyone recommend any tutorials or articles? Should I use SAX or DOM to do it?

[Pavel Halas]

I recommend you legendary tutorial/faq web by Roseanne Zhang.
My opinion is to use JDOM, parsing this way...

Document doc = null;
SAXBuilder parser = null;
try {
parser = new SAXBuilder();
parser.setIgnoringElementContentWhitespace(true);
doc = parser.build(file);
}

[Chris Stewart]

Ok, after some reading, here I am...
For some reason the node_x.getNodeValue call doesn't return the text, can anybody help me figure out why?

import org.w3c.dom.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import java.io.IOException;
public class Parse
{
  public static void main(String[] args) throws ParserConfigurationException, IOException, SAXException
  {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document document = builder.parse("http://rss.com.com/2547-12-0-5.xml");
    NodeList nodes_i = document.getDocumentElement().getChildNodes();
    for(int i = 0; i < nodes_i.getLength(); i++)
    {
      Node node_i = nodes_i.item(i);
      if(node_i.getNodeType() == Node.ELEMENT_NODE && ((Element)node_i).getTagName().equals("channel"))
      {
        Element itemChild = (Element)node_i;
        NodeList nodes_j = itemChild.getChildNodes();
        for(int j = 0; j < nodes_j.getLength(); j++)
        {
          Node node_j = nodes_j.item(j);
          if(node_j.getNodeType() == Node.ELEMENT_NODE && ((Element)node_j).getTagName().equals("item"))
          {
            System.out.println("\nIn a title tag!");
            Element pieces = (Element)node_j;
            NodeList nodes_x = pieces.getChildNodes();
            for(int x = 0; x < nodes_x.getLength(); x++)
            {
              Node node_x = nodes_x.item(x);
              if(node_x.getNodeType() == Node.ELEMENT_NODE)
              {
                System.out.println(node_x.getNodeName() + ": " + node_x.getNodeValue());
              }
            }
          }
        }
      }
    }
  }
}

[fei long]

If I am remember correctly, the 'ELEMENT' node type has broader range. So can you check the nodetype static variable again and try 'TEXTNODE' or something like that? Hope this helps you.

[Chris Stewart]

That didn't work for me either. :dunno:
[ July 21, 2003: Message edited by: Chris Stewart ]

[Naren]

in the inner most loop of your code, you got to the point where you can print the node name. For example, "title"
<title>Open source or no: Let the market decide</title>
The node you are examining at this point has a node name "title" and node value "null". I assume you are trying to print the text "Open source....".
It is represented by the child node and this child node has a node name "#text" (or null for some parsers) and the node value "Open source..."
To get your program working, get the child node, check it's Node type (Node.TEXT_NODE) and then get the NodeValue.

[Chris Stewart]

Perfect, thank you! This is my final code:

public static void main(String[] args) throws ParserConfigurationException, IOException, SAXException
  {
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document document = builder.parse("http://rss.com.com/2547-12-0-5.xml");
    NodeList nodes_i = document.getDocumentElement().getChildNodes();
    for(int i = 0; i < nodes_i.getLength(); i++)
    {
      Node node_i = nodes_i.item(i);
      if(node_i.getNodeType() == Node.ELEMENT_NODE && ((Element)node_i).getTagName().equals("channel"))
      {
        Element itemChild = (Element)node_i;
        NodeList nodes_j = itemChild.getChildNodes();
        for(int j = 0; j < nodes_j.getLength(); j++)
        {
          Node node_j = nodes_j.item(j);
          if(node_j.getNodeType() == Node.ELEMENT_NODE && ((Element)node_j).getTagName().equals("item"))
          {
            System.out.println("\nIn a title tag!");
            Element pieces = (Element)node_j;
            NodeList nodes_x = pieces.getChildNodes();
            for(int x = 0; x < nodes_x.getLength(); x++)
            {
              Node node_x = nodes_x.item(x);
              if(node_x.getNodeType() == Node.ELEMENT_NODE)
              {
                Element more = (Element)node_x;
                NodeList child = more.getChildNodes();
                for(int z = 0; z < child.getLength(); z++)
                {
                  Node node_z = child.item(z);
                  if(node_z.getNodeType() == Node.TEXT_NODE)
                  {
                    Text text = (Text)node_z;
                    System.out.println(text.getNodeName() + ": " + text.getNodeValue());
                  }
                }
              }
            }
          }
        }
      }
    }
  }

[Naren]

you can remove a lot of lines from your code using the call getElementsByTagName("tag_name").
I use this function to get the value of a node:

  public String getElementValue(Node e) {
    String value = "";
    NodeList nlist = e.getChildNodes();
    for(int i = 0; i < nlist.getLength(); i++) {
      Node textnode = nlist.item(i);
      if(textnode != null && textnode.getNodeType() == Node.TEXT_NODE) {
        value += textnode.getNodeValue();
      }
    }
    return value;
  }

the 'for' loop inside is just to be safe with all sorts of parser implementations. The text value of the node is represented, some times, in multiple child nodes.

[Cindy Glass]

Moving to the XML forum.