XML XSD Schema Validation with Xerces

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This section provides a tutorial example on how to write a XML schema validation program, XMLReaderValidator.java, with the Xerces parser.

Unfortunately, I couldn't find any XML parsers provided in J2SDK 1.4.1_02 that can validate XML structure against XSD rules. So I downloaded one of the most popular XML parsers in the public domain, xerces-j 2.3.0, at: http://xml.apache.org/dist/xerces-j.

Once I downloaded Xerces-J-bin.2.3.0.zip, I unzipped it into \local\xerces-2_3_0 directory. Make sure that xercesImpt.jar is in that directory.

Now I am ready to write a simple Java program to use "org.apache.xerces.parsers.SAXParser" to validate any XML files against the specified XSD files:

/**
 * XMLReaderValidator.java
 * Copyright (c) 2002 by Dr. Herong Yang
 */
import java.io.IOException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
class XMLReaderValidator {
   public static void main(String[] args) {
      String parserClass = "org.apache.xerces.parsers.SAXParser";
      String validationFeature 
         = "http://xml.org/sax/features/validation";
      String schemaFeature 
         = "http://apache.org/xml/features/validation/schema";
      try {
      	 String x = args[0];
         XMLReader r = XMLReaderFactory.createXMLReader(parserClass);
         r.setFeature(validationFeature,true);
         r.setFeature(schemaFeature,true);
         r.setErrorHandler(new MyErrorHandler());
         r.parse(x);
      } catch (SAXException e) {
         System.out.println(e.toString()); 
      } catch (IOException e) {
         System.out.println(e.toString()); 
      }
   }
   private static class MyErrorHandler extends DefaultHandler {
      public void warning(SAXParseException e) throws SAXException {
         System.out.println("Warning: "); 
         printInfo(e);
      }
      public void error(SAXParseException e) throws SAXException {
         System.out.println("Error: "); 
         printInfo(e);
      }
      public void fatalError(SAXParseException e) throws SAXException {
         System.out.println("Fattal error: "); 
         printInfo(e);
      }
      private void printInfo(SAXParseException e) {
         System.out.println("   Public ID: "+e.getPublicId());
         System.out.println("   System ID: "+e.getSystemId());
         System.out.println("   Line number: "+e.getLineNumber());
         System.out.println("   Column number: "+e.getColumnNumber());
         System.out.println("   Message: "+e.getMessage());
      }
   }
}

Note that:

• I used the XMLReaderFactory.createXMLReader() method to create an XMLReader with the Xerces parser class.
• I also used XMLReader.setFeature() to turn on two features: "validation" and "validation schema".
• Of course, I need to use XMLReader.setErrorHandler() to provide my own parser error handler.

See the next section to see test result of XMLReaderValidator.java.

Last update: 2006.

Sections in This Chapter

XML XSD Schema Validation with Xerces

XML XSD Schema Validation Test Result

Loading External XML Parsers with SAXParserFactory