无法将xml字符串转换为w3c doc

Question

I want to convert an java string containing xml to a w3c dom document object.

I first searched all over the place and came up with some good examples here on stackoverflow. But sadly I can get them working!

Apperently my code is not working 100%.

It seems like it parses the string but there are no values in the nodes. This is what I got so far!

Document newDoc = null;

InputSource is = new InputSource();
is.setCharacterStream(new StringReader(TestFiles.RSS_FEED_FILE_2));

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = null;
builder = factory.newDocumentBuilder();
newDoc = builder.parse(is);

When I do a sysout afterwards like this:

System.out.println(newDoc.getDocumentElement().getElementsByTagName("channel").item(0)
.getNodeValue());

I got null as output while using this sysout:

System.out.println(newDoc.getDocumentElement().getElementsByTagName("channel").item(0));

I got as output: [channel: null]

So I have an object else it would throw some null pointer exceptions but it doesn't contain any values inside ?!

The content of the constant is this :

public final static String RSS_FEED_FILE_2 =    "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + 
                                            "<rss version=\"2.0\">\n" + 
                                            "<channel>\n" + 
                                            "<title>sunday</title>\n" + 
                                            "<link>http://www.google.nl</link>\n" + 
                                            "<pubDate>2012-02-05 20:58</pubDate>\n" + 
                                            "<lastBuildDate>2012-02-08 09:48</lastBuildDate>\n" + 
                                            "<description>blabla </description>\n" + 
                                            "<item>\n" + 
                                            "<title><![CDATA[title]]></title>\n" + 
                                            "<link><![CDATA[http://www.google.nl]]></link>\n" + 
                                            "<guid><![CDATA[2266610]]></guid>\n" + 
                                            "<source><![CDATA[sunday]]></source>\n" + 
                                            "<author><![CDATA[me]]></author>\n" + 
                                            "<description><![CDATA[blalbalavblabllllll!]]></description>\n" + 
                                            "</item>\n" + 
                                            "</channel>\n" + 
                                            "</rss>";

Does anybody have a solution or a hint?

Answer 1

This is quite a common gotcha. The behaviour of getNodeValue() depends on the subclass of Node . In the case of an Element , getNodeValue() will always return null (see the table in the Node javadoc for behaviour of other subclasses).

Consider using getTextContent() if you want to debug the XML document.

Answer 2

As you are trying to load an RSS XML string, I can suggest you to use RSS XSD from http://www.thearchitect.co.uk/schemas/rss-2_0.xsd . This will help you in loading the RSS string and giving you a better way to either edit data or transform it to any destinations like file. This will need JAXB to work although. Hope this helps.

Answer 3

Using jdom takes a lot of pain of out processing XML, and it is usually my first port of call.

If using jdom is an option, then building the document is trivial.

SAXBuilder builder = new SAXBuiler();
Document doc = builder.build(new StringReader(YOUR_XML_STRING));

The thing to be careful of is that this creates an org.jdom.Document object, which you then need to adapt in to a w3c document. Again this is quite easily achieved with the org.jdom.output.DOMOutputter class.