SAX problem

[John Coleman]

I get
java.lang.NullPointerException
at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1132)
at com.abnamro.wcs.orchard.gui.madj.ImportXMLFile.main(ImportXMLFile.java:179)
Exception in thread "main"
from the code below. I copied the source from the JAXP example so I cannot understand why it does not work. What is missing?
Any help much appreciated. Please reply to address below.

// JAXP packages
import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
 
import java.util.*;
import java.io.*;
import java.net.MalformedURLException;
 
public class ImportXMLFile extends DefaultHandler implements MADJFileTags{
 
    /** A Hashtable with tag names as keys and Integers as values */
    static private Hashtable journalInfo;
 
    static String section;
 
    static MADJJournal journal;
    static MADJJournalHeader journalHeader;
    static MADJJournalDetail journalDetail;
 
    /* these constants identify the child tags of the root node */
    static final String INFO =
      ConnectionManager.props.getProperty(INFO_TAG, INFO_TAG);
    static final String HEADER =
      ConnectionManager.props.getProperty(HEADER_TAG, HEADER_TAG);
    static final String LINE_DETAIL =
      ConnectionManager.props.getProperty(LINE_DETAIL_TAG, LINE_DETAIL_TAG);
    /* this constant identifies the journal line tag */
    static final String LINE =
      ConnectionManager.props.getProperty(LINE_TAG, LINE_TAG);
 
    // Parser calls this once at the beginning of a document
    public void startDocument() throws SAXException {
      journal = new MADJJournal();
    }
 
    // Parser calls this for each element in a document
    public void startElement(String namespaceURI, String localName,
                                                  String qName, Attributes atts)
            throws SAXException
    {
 
    /* indicate the child of the root node in section */
    if (localName.equals(INFO))
      {
      section = INFO;
      return;
      }
 
    if (localName.equals(HEADER))
      {
      section = HEADER;
      journalHeader = journal.getJournalHeader(); // initiate header
      return;
      }
 
    if (localName.equals(LINE_DETAIL))
      {
      section = LINE_DETAIL;
      return;
      }
 
    /* deal with MADJ_INFO children by setting variables up */
    if (section.equals(INFO))
      {
      journalInfo.put(localName, atts.getValue(ATR_VAL));
      return;
      }
 
    /* deal with MADJ_HEADER children by setting variables up */
    if (section.equals(HEADER))
      {
      journalHeader.setJournalColumn(localName, atts.getValue(ATR_VAL));
      return;
      }
 
    /* deal with MADJ_LINE_DETAIL children by storing values */
    if (section.equals(LINE_DETAIL))
      {
      /* deal with the MADJ_LINE tag */
      if (localName.equals(LINE))
        {
        journalDetail = new MADJJournalDetail();
        return;
        }
      else
        {
        journalDetail.setJournalColumn(localName, atts.getValue(ATR_VAL));
        return;
        }
      }
 
    } // startElement method end
 
    // Parser calls this for each element in a document
    public void endElement(String namespaceURI, String localName,
                                                  String qName, Attributes atts)
            throws SAXException
    {
    /* indicate the end of child of the root node */
    if (localName.equals(INFO)) section = "";
    if (localName.equals(HEADER)) section = "";
    if (localName.equals(LINE_DETAIL)) section = "";
    if (localName.equals(LINE)) journal.setJournalDetailLine(journalDetail);
    }
 
    // Parser calls this once after parsing a document
    public void endDocument() throws SAXException
    {
 
    /* create the Journal */
 
    }
 
    /**
     * Convert from a filename to a file URL.
     */
    private static String convertToFileURL(String aFileName) {
      String path = "";
        try {
          path = new File(aFileName).toURL().toString();
          } catch (MalformedURLException e) {System.out.println(e);}
        return path;
    }
 
//    static public MADJJournal ParseXMLFile(String aFileName) throws Exception {
    static public void main(String[] args) throws Exception {
//        String aFileName = "E:\\DEV\\Transfer\\gbcomn\\MADJ_Journal.xml";
        String aFileName = "F:\\PMU\\Central Services\\Finance Architecture"
                + "\\MAdjustments\\MAdjustments\\MADJ_Journal.xml";
 
    try {
      ConnectionManager.getDBConnection("OGU",
                                        "jdbc:oracle:thin:@fpdbln98:1521:ORCDEV01",
                                        "oracle.jdbc.driver.OracleDriver",
                                        "ogadev", "ogadev");
      } catch (Exception e) {System.out.println(e);}
 
        boolean dtdValidate = false;
 
// use the properties to allocate SAX Parser
        System.setProperty(XML_FACTORY, ConnectionManager.props.getProperty(XML_FACTORY));
 
        String sValidate = ConnectionManager.props.getProperty(XML_VALIDATION);
        /* set the validation from the property */
        if (sValidate != null && sValidate.compareToIgnoreCase("TRUE")==0)
          dtdValidate = true;
 
        // Create a JAXP SAXParserFactory and configure it
        SAXParserFactory spf = SAXParserFactory.newInstance();
 
        // Set namespaceAware to true to get a parser that corresponds to
        // the default SAX2 namespace feature setting.  This is necessary
        // because the default value from JAXP 1.0 was defined to be false.
        spf.setNamespaceAware(true);
 
        // Validation part 1: set whether validation is on
        spf.setValidating(dtdValidate);
 
        // Create a JAXP SAXParser
        SAXParser saxParser = spf.newSAXParser();
 
        // Get the encapsulated SAX XMLReader
        XMLReader xmlReader = saxParser.getXMLReader();
 
        // Set the ContentHandler of the XMLReader
        xmlReader.setContentHandler(new ImportXMLFile());
 
        // Set an ErrorHandler before parsing
        xmlReader.setErrorHandler(new MyErrorHandler(System.err));
 
        // Tell the XMLReader to parse the XML document
        xmlReader.parse(convertToFileURL(aFileName));
 
//        return journal;
    }
 
    // Error handler to report errors and warnings
    private static class MyErrorHandler implements ErrorHandler {
        /** Error handler output goes here */
        private PrintStream out;
 
        MyErrorHandler(PrintStream out) {
            this.out = out;
        }
 
        /**
         * Returns a string describing parse exception details
         */
        private String getParseExceptionInfo(SAXParseException spe) {
            String systemId = spe.getSystemId();
            if (systemId == null) {
                systemId = "null";
            }
            String info = "URI=" + systemId +
                " Line=" + spe.getLineNumber() +
                ": " + spe.getMessage();
            return info;
        }
 
        // The following methods are standard SAX ErrorHandler methods.
        // See SAX documentation for more info.
 
        public void warning(SAXParseException spe) throws SAXException {
            out.println("Warning: " + getParseExceptionInfo(spe));
        }
 
        public void error(SAXParseException spe) throws SAXException {
            String message = "Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        }
 
        public void fatalError(SAXParseException spe) throws SAXException {
            String message = "Fatal Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        }
    }

reply to:
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[ April 29, 2002: Message edited by: Jim Yingst ]

[John Wetherbie]

I'm having difficulty locating line 179 where the exception is thrown. COuld you mark it someway?
It sounds like something is not being created properly but what the reason is is hard to say.
John

[Jim Yingst]

Ugh. That was too much work just to get the code looking semi-presentable. Anyway, the exception must have been thrown by the line
xmlReader.parse(convertToFileURL(aFileName));
as that's the only place parse() is called. But it's not really clear what the cause is.

[John Coleman]

Jim,
You are correct that the error occurs in the .parse method, and also that there is no way of diagnosing the error.
This makes me wonder if the Sax example in JAXP works. I also wonder if anyone unserstands Sax enough to tell me what is missing? Should I contact the author?
John

[John Coleman]

The problem is solved. Although the error message appears to point to a problem in the .parse method, in reality it is the methods that I override that cause the error. In this case a stepwise debug reveals that a string variable was not initialised before use in .startElement method.
The moral of the tale is not to let cryptic error messages put you off running a debug or looking for obvious mistakes.
thanks anyway,
John