SAXValidator.java - Validating XML with DTD using SAX

This section provides a tutorial example on how to use SAX API provided in JDK 1.4 to write a Java program to validate an XML document against the specified DTD document type.

Actually, SAX and DOM are sharing the same XML validation implementation. In this implementation, error events are fired during the parsing process. Application programs that are interested in validation errors must implement the error event handlers defined in the org.xml.sax.ErrorHandler interface.

In the SAX design, the ErrorHandler interface is integrated into the DefaultHandler class. Application programs just need to extend DefaultHandler and override those error event handlers.

Here is my SAX based XML validation program, SAXValidator.java:

/* SAXValidator.java
 - Copyright (c) 2014, HerongYang.com, All Rights Reserved.
 */
import java.io.File;
import java.io.IOException;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;
class SAXValidator {
   public static void main(String[] args) {
      try {
         File x = new File(args[0]);
         SAXParserFactory f = SAXParserFactory.newInstance();
         f.setValidating(true); // Default is false         
         SAXParser p = f.newSAXParser();
         DefaultHandler h = new MyErrorHandler();
         p.parse(x,h);
      } catch (ParserConfigurationException e) {
         System.out.println(e.toString()); 
      } 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:

Run "java SAXValidator invalid_dtd.xml", you will get the same output as DOMValidator.java described in the previous section.

Last update: 2014.

Table of Contents

 About This Book

 Introduction of XML (eXtensible Markup Language)

 XML File Syntax

 XML File Browsers

 DOM (Document Object Model) Programming Interface

 SAX (Simple API for XML) Programming Interface

 DTD (Document Type Definition) Introduction

 Syntaxes of DTD Statements

Validating an XML Document against the Specified DTD Document Type

 DOMValidator.java - Validating XML with DTD using DOM

SAXValidator.java - Validating XML with DTD using SAX

 XSD (XML Schema Definition) Introduction

 Syntaxes of XSD Statements

 Validating XML Documents Against Specified XML Schemas

 XSL (Extensible Stylesheet Language) Introduction

 XSLT (XSL Transformations) Introduction

 Java Implementation of XSLT

 XPath (XML Path) Language

 XSLT Elements as Programming Statements

 Control and Generate XML Element in the Result

 XML Notepad - XML Editor

 XML Tools Plugin for Notepad++

 XML 1.1 Changes and Parsing Examples

 Outdated Tutorials

 References

 PDF Printing Version