DO NOT REPLY [Bug 15218] New: - XPathApi.selectNodeList throws NullPointerException

[bu...@apache.org]

DO NOT REPLY TO THIS EMAIL, BUT PLEASE POST YOUR BUG 
RELATED COMMENTS THROUGH THE WEB INTERFACE AVAILABLE AT
<http://nagoya.apache.org/bugzilla/show_bug.cgi?id=15218>.
ANY REPLY MADE TO THIS MESSAGE WILL NOT BE COLLECTED AND 
INSERTED IN THE BUG DATABASE.

http://nagoya.apache.org/bugzilla/show_bug.cgi?id=15218

XPathApi.selectNodeList throws NullPointerException

           Summary: XPathApi.selectNodeList throws NullPointerException
           Product: XalanJ2
           Version: 2.4
          Platform: Other
        OS/Version: Other
            Status: NEW
          Severity: Normal
          Priority: Other
         Component: org.apache.xml.dtm
        AssignedTo: xalan-dev@xml.apache.org
        ReportedBy: David.Ostrovsky@dvg.de


Since version xalan 2-4-0 (also in version 2-4-1) I'm getting a 
NullPointerException:

Exception in thread "main" java.lang.NullPointerException
        at org.apache.xml.dtm.ref.DTMNodeList.item(DTMNodeList.java:164)
        at ApplyXPath2.doMain(ApplyXPath2.java:134)
        at ApplyXPath2.main(ApplyXPath2.java:164)

Here is what I'm doing:
           NodeList nl = XPathAPI.selectNodeList(doc, xpath);
            int index = 0;
            for (; nl.item(index) != null; index++);

With XPathAPI.slectNodeIterator(..) i've no problems.

Tested XML document (in distribution xalan-j_2_4_1/samples/ApplyXPath)

<?xml version="1.0"?>
<doc>
  <name first="David" last="Marston"/>
  <name first="David" last="Bertoni"/>
  <name first="Donald" last="Leslie"/>
  <name first="Emily" last="Farmer"/>
  <name first="Joseph" last="Kesselman"/>
  <name first="Myriam" last="Midy"/>
  <name first="Paul" last="Dick"/>
  <name first="Stephen" last="Auriemma"/>
  <name first="Scott" last="Boag"/>
  <name first="Shane" last="Curcuru"/>
</doc>

Source Code:
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Properties;
import org.apache.xerces.parsers.DOMParser;
import org.apache.xpath.XPathAPI;
import org.apache.xml.utils.TreeWalker;
import org.apache.xml.utils.DOMBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.DocumentFragment;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.traversal.NodeIterator;
import org.xml.sax.SAXException;
import org.xml.sax.InputSource;

// Imported JAVA API for XML Parsing 1.0 classes
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException; 

// Imported Serializer classes
import javax.xml.transform.*;
import javax.xml.transform.stream.*;
import javax.xml.transform.dom.*;

/**
 *  Very basic utility for applying an XPath epxression to an xml file and 
printing information
 /  about the execution of the XPath object and the nodes it finds.
 *  Takes 2 arguments:
 *     (1) an xml filename
 *     (2) an XPath expression to apply to the file
 *  Examples:
 *     java ApplyXPath foo.xml /
 *     java ApplyXPath foo.xml /doc/name[1]/@last
 * @see XPathAPI
 */
public class ApplyXPath2
{
    protected String filename = null;
    protected String xpath = null;

    /** Process input args and execute the XPath.  */
    public void doMain(String[] args)
    throws Exception
    {
        filename = args[0];
        xpath = args[1];

        if ((filename != null) && (filename.length() > 0)
            && (xpath != null) && (xpath.length() > 0))
        {
            // Tell that we're loading classes and parsing, so the time it 
            // takes to do this doesn't get confused with the time to do 
            // the actual query and serialization.
            System.out.println("Loading classes, parsing "+filename+", and 
setting up serializer");
      
            // Set up a DOM tree to query.
            InputSource in = new InputSource(new FileInputStream(filename));
            DocumentBuilderFactory dfactory = 
DocumentBuilderFactory.newInstance();
            dfactory.setNamespaceAware(true);
            Document doc = dfactory.newDocumentBuilder().parse(in);
      
            // Set up an identity transformer to use as serializer.
            Transformer serializer = 
TransformerFactory.newInstance().newTransformer();
            serializer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, 
"yes");

            // Use the simple XPath API to select a nodeIterator.
            System.out.println("Querying DOM using "+xpath);
            NodeList nl = XPathAPI.selectNodeList(doc, xpath);

            // Serialize the found nodes to System.out.
            System.out.println("<output>");

            int index = 0;
            for (; nl.item(index) != null; index++);
            System.out.println("Found "+index+" applicationentries");
            System.out.println("</output>");
        }
        else
        {
            System.out.println("Bad input args: " + filename + ", " + xpath);
        }
    }
    
    /** Decide if the node is text, and so must be handled specially */
    static boolean isTextNode(Node n) {
        if (n == null)
            return false;
        short nodeType = n.getNodeType();
        return nodeType == Node.CDATA_SECTION_NODE || nodeType == 
Node.TEXT_NODE;
    }
    
    /** Main method to run from the command line.    */
    public static void main (String[] args)
    throws Exception
    {
        if (args.length != 2)
        {
            System.out.println("java ApplyXPath filename.xml xpath\n"
                + "Reads filename.xml and applies the xpath; prints the nodelist 
found.");
            return;
        }
        
        ApplyXPath2 app = new ApplyXPath2();
        app.doMain(args);
    }
  
} // end of class ApplyXPath

Program call:

java ApplyXPath2 foo.xml /