DocumentBuilder.parse not working for String input

[Steve McRoberts]

I'm trying to do a server-side xsl transform of an xml string.
But, no matter what I try, I can't get the xml string into a Document. I don't get an error, but the Document is always empty; somehow the parse is not taking the String.
Here is the pertinent code:

import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.Document;

	DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
	DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
	Document document = docBuilder.parse( new ByteArrayInputStream( new String( "<doc><name>Steve</name></doc>" ).getBytes() ) );		

After running this, when I examine the contents of document's internal StringBuffer it is null.
What irks me is that at one point I did have the magical combination that made this work, but I lost the code.
Can someone help me with this, or show me a better way? Eventually I just need to be able to take an xml string and an xsl string and do the transform on the servlet and send out a finished HTML to a mobile device.

[William Brogden]

You may be running into a common trap.

Document nodes return null for the nodeValue - see the very useful table in the org.w3c.dom.Node JavaDocs.

If you didn't get a parse error, your Document is probably ok, you just need to use the various Document, Element and Node methods to get at the contents.

Bill

[Steve McRoberts]

Thanks Bill, but I don't think that's it. It's not just that the document appears empty, but when I use it I get the Browser error "XML document must have a top level element.".

I've tried numerous ways to populate the document with the XML to no avail. Currently I'm using the stringToDom utility I found here at the ranch. Here's the complete class:

import java.io.StringReader;
import java.io.StringWriter;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import org.w3c.dom.Document;

public class TransformXML {
	public String transformXML(String xmlString, String xslString) {

		StringWriter stw = new StringWriter();

		try {
			// Get the XML string into a real XML document:
			Document document = Util.stringToDom(xmlString);

			// Get a Source for the document:
			Source xmlSource = new DOMSource(document);
			
			// Get the XSL from a string into a StreamSource for Transform to use:
			StringReader xslReader = new StringReader(xslString);
			StreamSource stylesource = new StreamSource(xslReader);

			// Setup the result for the Transform's use:
			StreamResult result = new StreamResult(stw);
			result.setWriter(stw);
			
			// Use a Transformer for output
			TransformerFactory tFactory = TransformerFactory.newInstance();
			Transformer transformer = tFactory.newTransformer(stylesource);
			transformer.transform(xmlSource, result);
			
			// Return the result as a [html] string:
			return stw.toString();
		} catch (Exception e) {
			System.out.println(e);
			return null;
		}
	}
}

The stringToDom method is defined as:

import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.xml.sax.*;

public class Util {

    public static Document stringToDom(String xmlSource) 
            throws SAXException, ParserConfigurationException, IOException {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        return builder.parse(new InputSource(new StringReader(xmlSource)));
    }
}

And I'm calling it from a servlet as follows:

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		TransformXML transformXML = new TransformXML();
		String xml = "<doc><name>Steve</name></doc>";
		String xsl = 
			"<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\" >"+
			"<xsl:template match=\"/\">"+	
			"<xsl:value-of select=\"local-name()\" />"+
			"</xsl:template>"+
			"</xsl:stylesheet>";
		PrintWriter out = response.getWriter();
		out.println(transformXML.transformXML(xml, xsl));
	}

[Paul Clapham]

Steve McRoberts wrote:I'm trying to do a server-side xsl transform of an xml string.

In which case I don't understand why you are trying to parse the XML into a Document...

[Steve McRoberts]

Paul Clapham wrote:

Steve McRoberts wrote:I'm trying to do a server-side xsl transform of an xml string.

In which case I don't understand why you are trying to parse the XML into a Document...

Paul, it's because the Transformer.transform takes a Source as an input, and I'm using DOMSource() to obtain the Source, and it requires a document.
Is there a short-cut I'm missing? Can I get transform() to take my xml-string directly as a Source?

[g tsuji]

You've to make good the transformation!
"<xsl:value-of select=\"local-name()\" />"+
should be at least read as this
"<xsl:value-of select=\"local-name(*)\" />"+
if you want to read out the "doc", even though it is really awkward, but at least it should work that way.

[Paul Clapham]

Steve McRoberts wrote:Paul, it's because the Transformer.transform takes a Source as an input, and I'm using DOMSource() to obtain the Source, and it requires a document.
Is there a short-cut I'm missing? Can I get transform() to take my xml-string directly as a Source?

I wouldn't call it a "short-cut"; look at the documentation for Source and you'll see three classes which implement it. You chose DOMSource but look at the others. StreamSource? There's a StreamSource constructor which accepts a Reader. Now go on over to the documentation for Reader and scroll down about... there's a thing called StringReader.

[Steve McRoberts]

g tsuji wrote:You've to make good the transformation!
"<xsl:value-of select=\"local-name()\" />"+
should be at least read as this
"<xsl:value-of select=\"local-name(*)\" />"+
if you want to read out the "doc", even though it is really awkward, but at least it should work that way.

Thanks, g! This gets me further. I never would've suspected a typo in the xsl! So, it evidently is taking my XML, because I see "doc" in the new Browser error:

The XML page cannot be displayed
Cannot view XML input using style sheet. Please correct the error and then click the Refresh button, or try again later.


--------------------------------------------------------------------------------

Invalid at the top level of the document. Error processing resource 'http://localhost:8080/RawsM/Detail'. Line 1, Position...

<?xml version="1.0" encoding="UTF-8"?>doc
--------------------------------------^

The thing is: I don't want the browser to treat this as an XML file. I want it to be html: it need not be aware that the html was generated from xml/xsl. For now, I just want it to spit out the tag-names and their values, such as:
name Steve

[Paul Clapham]

The browser is correct, your output isn't well-formed XML. But if you want the browser to treat it as HTML, you should set the content type of the response to text/html.

Edit: You might also consider not writing out the prolog, and you might even consider producing well-formed HTML. Check out the <xsl:output> element for useful features.

[g tsuji]

That kind of error is inevitable if you stick to that kind of primitive defective xsl. The minimum proper rendering can be this.

        String xsl =    
            "<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\" >"+   
            "<xsl:output method=\"html\" omit-xml-declaration=\"yes\"  />" +
            "<xsl:template match=\"/\">"+    
            "<html><body><div>" + 
            "<xsl:value-of select=\"doc/name\" />"+   
            "</div></body></html>" +
            "</xsl:template>"+   
            "</xsl:stylesheet>";   

Then you should have at least a proper html test case, however primitive one can still blame it!

[Steve McRoberts]

This community rocks! Thanks to everyone for the great response! Together you have resolved my issue.