NullPointerException

From:

ramu <ramu.ask@gmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 02 Aug 2007 08:26:23 -0700

Message-ID:

<1186068383.230232.293360@x40g2000prg.googlegroups.com>

Hi,
     I want to validate an xml document against an XSD. The program is
written in java.
Below is the program:

package transform;

import oracle.xml.schemavalidator.XSDValidator;
import oracle.xml.parser.schema.XSDException;
import oracle.xml.parser.schema.XMLSchema;
import oracle.xml.parser.schema.XSDBuilder;
import oracle.xml.parser.v2.XMLError;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;
import java.net.URL;

public class SchemaValidator{

        public void validateSchema(String SchemaUrl, String
XmlDocumentUrl)
        {
                try {
                        XSDValidator xsdValidator=new XSDValidator();
                        XSDBuilder builder = new XSDBuilder();
                        URL url = new URL(SchemaUrl);
                        XMLSchema schemadoc =
(XMLSchema)builder.build(url);
                        xsdValidator.setSchema(schemadoc);

                        Validator handler=new Validator();
                        XMLError xmlError=new XMLError();
                        xmlError.setErrorHandler(handler);
                        xsdValidator.setError(xmlError);
                        xsdValidator.validate(new
URL(XmlDocumentUrl));
                        if(handler.validationError==true)
                                System.out.println("This XML Document
has Error: " + handler.saxParseException.getMessage());
                        else
                                System.out.println("This XML Document
is valid");

                }
                catch(java.io.IOException ioe)
                {
                        System.out.println("IOException
"+ioe.getMessage());
                }catch (SAXException e) {
                        System.out.println("SAXException
"+e.getMessage());
                }
                catch (XSDException e) {
                        System.out.println("SAXException
"+e.getMessage());
                }
        }

        private class Validator extends DefaultHandler{

                public boolean validationError = false;
                public SAXParseException saxParseException=null;

        public void error(SAXParseException exception) throws
SAXException{
                validationError = true;
                saxParseException=exception;
                }

                public void fatalError(SAXParseException exception)
throws SAXException{
            validationError = true;
            saxParseException=exception;
                }
                public void warning(SAXParseException exception)
throws SAXException{}

           }

        public static void main(String[] argv){
                String SchemaUrl=argv[0];
                String XmlDocumentUrl=argv[1];
                SchemaValidator validator=new SchemaValidator();
                validator.validateSchema(SchemaUrl, XmlDocumentUrl);

        }
}

When some attributes are missing in the XML document ,which is to be
validated, it is giving NullPointerException.

Exception in thread "main" java.lang.NullPointerException
        at oracle.xml.parser.v2.XMLError.flushNodes(XMLError.java:351)
        at
oracle.xml.parser.schema.XSDValidator.sendDOMError(XSDValidator.java:
1749)
        at
oracle.xml.parser.schema.XSDValidator.error(XSDValidator.java:1713)
        at
oracle.xml.parser.schema.XSDValidator.validateAttribute(XSDValidator.java:
671)
        at
oracle.xml.parser.schema.XSDValidator.startElement(XSDValidator.java:
534)
        at
oracle.xml.parser.v2.XMLElement.reportStartElement(XMLElement.java:
3066)
        at
oracle.xml.parser.v2.XMLElement.reportSAXEvents(XMLElement.java:2937)
        at
oracle.xml.parser.v2.XMLElement.reportChildSAXEvents(XMLElement.java:
2950)
        at
oracle.xml.parser.v2.XMLElement.reportSAXEvents(XMLElement.java:2939)
        at
oracle.xml.parser.v2.XMLElement.reportChildSAXEvents(XMLElement.java:
2950)
        at
oracle.xml.parser.v2.XMLElement.reportSAXEvents(XMLElement.java:2939)
        at
oracle.xml.parser.v2.XMLElement.reportChildSAXEvents(XMLElement.java:
2950)
        at
oracle.xml.parser.v2.XMLElement.reportSAXEvents(XMLElement.java:2939)
        at
oracle.xml.parser.v2.XMLElement.reportChildSAXEvents(XMLElement.java:
2950)
        at
oracle.xml.parser.v2.XMLDocument.reportSAXEvents(XMLDocument.java:
1389)
        at
oracle.xml.schemavalidator.XSDValidator.validate(XSDValidator.java:97)
        at
oracle.xml.schemavalidator.XSDValidator.validate(XSDValidator.java:
163)
        at
transform.SchemaValidator.validateSchema(SchemaValidator.java:28)
        at transform.SchemaValidator.main(SchemaValidator.java:68)

Instead of throwing NullPointerException, I want an proper error
message to be printed.
Can anyone please tell me how to do this?