SAXValidator.java - XML DTD Validation with SAX

This section provides a tutorial example on how to write a DTD validator using SAX classes in JDK. The validator can validate an XML file against the specified DTD statements.

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.

Last update: 2014.

Table of Contents

 About This JDK Tutorial Book

 Downloading and Installing JDK 1.8.0 on Windows

 Downloading and Installing JDK 1.7.0 on Windows

 Downloading and Installing JDK 1.6.2 on Windows

 Java Date-Time API

 Date, Time and Calendar Classes

 Date and Time Object and String Conversion

 Number Object and Numeric String Conversion

 Locales, Localization Methods and Resource Bundles

 Calling and Importing Classes Defined in Unnamed Packages

 HashSet, Vector, HashMap and Collection Classes

 Character Set Encoding Classes and Methods

 Character Set Encoding Maps

 Encoding Conversion Programs for Encoded Text Files

 Socket Network Communication

 Datagram Network Communication

 DOM (Document Object Model) - API for XML Files

 SAX (Simple API for XML)

DTD (Document Type Definition) - XML Validation

 DOMValidator.java - XML DTD Validation with DOM

 Testing DOM XML DTD Validator

SAXValidator.java - XML DTD Validation with SAX

 XSD (XML Schema Definition) - XML Validation

 XSL (Extensible Stylesheet Language)

 Message Digest Algorithm Implementations in JDK

 Private key and Public Key Pair Generation

 PKCS#8/X.509 Private/Public Encoding Standards

 Digital Signature Algorithm and Sample Program

 "keytool" Commands and "keystore" Files

 KeyStore and Certificate Classes

 Secret Key Generation and Management

 Cipher - Secret Key Encryption and Decryption

 The SSL (Secure Socket Layer) Protocol

 SSL Socket Communication Testing Programs

 SSL Client Authentication

 HTTPS (Hypertext Transfer Protocol Secure)

 Outdated Tutorials

 References

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