Validate XML using a XSD (XML Schema)

Consider this XML file howto.xml :

<?xml version="1.0" encoding="ISO-8859-1"?>
<howto xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<topic>
<title>Java</title>
<url>http://www.rgagnon.com/topics/java-xml.html</url>
</topic>
<topic>
<title>PowerBuilder</title>
<url>http://www.rgagnon.com/topics/pb-powerscript.htm</url>
</topic>
<topic>
<title>Javascript</title>
<url>http://www.rgagnon.com/topics/js-language.html</url>
</topic>
<topic>
<title>VBScript</title>
<url>http://www.rgagnon.com/topics/wsh-vbs.html</url>
</topic>
</howto>

The external howto.xsd :

<?xml version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:element name="howto">
<xs:complexType>
<xs:sequence>
<xs:element name="topic" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="title" type="xs:string"/>
<xs:element name="url" type="httpURI"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>

<xs:simpleType name="httpURI">
<xs:restriction base="xs:anyURI">
<xs:pattern value="http://.*" />
</xs:restriction>
</xs:simpleType>

</xs:schema>

The code (using SAX parser) to validate an XML file using a given external XSD.

import java.io.IOException;

// SAX
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.XMLReader;

//SAX and external XSD
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.SchemaFactory;

import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.InputSource;

public class XMLUtils {

private XMLUtils() {}

// validate SAX and external XSD
public static boolean validateWithExtXSDUsingSAX(String xml, String xsd)
throws ParserConfigurationException, IOException
{
try {
SAXParserFactory factory = SAXParserFactory.newInstance();
factory.setValidating(false);
factory.setNamespaceAware(true);

SchemaFactory schemaFactory = SchemaFactory.newInstance("http://www.w3.org/2001/XMLSchema");
SAXParser parser = null;
try {
factory.setSchema(schemaFactory.newSchema(new Source[] {new StreamSource( xsd )}));
parser = factory.newSAXParser();
}
catch (SAXException se) {
System.out.println("SCHEMA : " + se.getMessage());  // problem in the XSD itself
return false;
}

XMLReader reader = parser.getXMLReader();
reader.setErrorHandler(
new ErrorHandler() {
public void warning(SAXParseException e) throws SAXException {
System.out.println("WARNING: " + e.getMessage()); // do nothing
}

public void error(SAXParseException e) throws SAXException {
System.out.println("ERROR : " + e.getMessage());
throw e;
}

public void fatalError(SAXParseException e) throws SAXException {
System.out.println("FATAL : " + e.getMessage());
throw e;
}
}
);
reader.parse(new InputSource(xml));
return true;
}
catch (ParserConfigurationException pce) {
throw pce;
}
catch (IOException io) {
throw io;
}
catch (SAXException se){
return false;
}
}

public static void main (String args[]) throws Exception{
System.out.println
(XMLUtils.validateWithExtXSDUsingSAX
("howto.xml", "howto.xsd"));
/*
output :
true
*/
}
}

The XML can contain a reference to the XSD to be used.

<?xml version="1.0" encoding="ISO-8859-1"?>
<howto xsi:noNamespaceSchemaLocation="howto.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<topic>
<title>Java</title>
<url>http://www.rgagnon.com/topics/java-xml.html</url>
</topic>
...
</howto>

The code (using DOM parser) to validate an XML file using the referenced XSD :