This section describes a tutorial example on how to create an error handler to be used by the validator to alter the default error handling behavior.
As you can see from the previous section, the default error handling behavior is to stop the validation
process immediately after the first error. This behavior is not very good. It prevents the user to collect
all possible validation errors in a single validation process.
In order to change this default behavior, we can create our own error handler as shown in the following
tutorial example:
/*
* XsdSchemaDomValidatorWithErrorHandler.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Schema;
import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import javax.xml.validation.Validator;
import javax.xml.transform.dom.DOMSource;
import java.io.File;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.ErrorHandler;
class XsdSchemaDomValidatorWithErrorHandler {
private static int errorCount = 0;
public static void main(String[] a) {
if (a.length<2) {
System.out.println("Usage:");
System.out.println("java XsdSchemaValidator schema_file_name "
+ "xml_file_name");
} else {
String schemaName = a[0];
String xmlName = a[1];
Schema schema = loadSchema(schemaName);
Document document = parseXmlDom(xmlName);
validateXml(schema, document);
}
}
public static void validateXml(Schema schema, Document document) {
try {
// creating a Validator instance
Validator validator = schema.newValidator();
System.out.println();
System.out.println("Validator Class: "
+ validator.getClass().getName());
// setting my own error handler
validator.setErrorHandler(new MyErrorHandler());
// validating the document against the schema
validator.validate(new DOMSource(document));
System.out.println();
if (errorCount>0) {
System.out.println("Failed with errors: "+errorCount);
} else {
System.out.println("Passed.");
}
} catch (Exception e) {
// catching all validation exceptions
System.out.println();
System.out.println(e.toString());
}
}
public static Schema loadSchema(String name) {
Schema schema = null;
try {
String language = XMLConstants.W3C_XML_SCHEMA_NS_URI;
SchemaFactory factory = SchemaFactory.newInstance(language);
schema = factory.newSchema(new File(name));
} catch (Exception e) {
System.out.println(e.toString());
}
return schema;
}
public static Document parseXmlDom(String name) {
Document document = null;
try {
DocumentBuilderFactory factory
= DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
document = builder.parse(new File(name));
} catch (Exception e) {
System.out.println(e.toString());
}
return document;
}
static class MyErrorHandler implements ErrorHandler {
public void fatalError( SAXParseException e )
throws SAXException {
System.out.println(e.toString());
throw e;
}
public void error( SAXParseException e ) throws SAXException {
System.out.println(e.toString());
errorCount++;
// continue with validatin process
// throw e;
}
public void warning( SAXParseException e ) throws SAXException {
System.out.println(e.toString());
}
}
}
Now try this new validator on the XML file, first_html_extra_attribute.xml:
>javac XsdSchemaDomValidatorWithErrorHandler.java
>java XsdSchemaDomValidatorWithErrorHandler first_html.xsd
first_html_extra_attribute.xml
org.xml.sax.SAXParseException: cvc-type.3.1.1:
Element 'body' is a simple type,
so it cannot have attributes, excepting those whose namespace name
is identical to 'http://www.w3.org/2001/XMLSchema-instance'
and whose [local name] is one of 'type', 'nil', 'schemaLocation'
or 'noNamespaceSchemaLocation'. However, the attribute, 'bgcolor'
was found.
org.xml.sax.SAXParseException: cvc-type.3.1.2:
Element 'body' is a simple type,
so it must have no element information item [children].
Failed with errors: 2
We have a much better XSD schema validator now. You could use it for your real XML applications.
