Unable to find a factory for http://www.w3.org/2001/XMLSchema

Question

I'm having some annoying problems with the following code, that worked okay until switched to Java 1.7

import javax.xml.validation.SchemaFactory;
SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

Running from Netbeans with -Djaxp.debug=1, the following error is thrown:

The above snipped code is part of an OSGI bundle

JAXP: using thread context class loader (sun.misc.Launcher$AppClassLoader@5e3a78ad) for search
JAXP: Looking up system property 'javax.xml.validation.SchemaFactory:http://www.w3.org/2001/XMLSchema'
JAXP: The property is undefined.
JAXP: found null in $java.home/jaxp.properties
JAXP: no META-INF/services/javax.xml.validation.SchemaFactory file was found
JAXP: attempting to use the platform default XML Schema validator
JAXP: instanciating org.apache.xerces.jaxp.validation.XMLSchemaFactory
JAXP: failed to instanciate org.apache.xerces.jaxp.validation.XMLSchemaFactory
java.lang.ClassNotFoundException: org.apache.xerces.jaxp.validation.XMLSchemaFactory
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at javax.xml.validation.SchemaFactoryFinder.createInstance(Unknown Source)
at javax.xml.validation.SchemaFactoryFinder._newFactory(Unknown Source)
at javax.xml.validation.SchemaFactoryFinder.newFactory(Unknown Source)
at javax.xml.validation.SchemaFactory.newInstance(Unknown Source)
JAXP: unable to find a factory for http://www.w3.org/2001/XMLSchema
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: http://www.w3.org/2001/XMLSchema

I have also made a small Java app with only the factory instance

SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

The factory is instance of "com.sun.org.apache.xerces.internal.jaxp.validation.XMLSchemaFactory" while in my bundle it tries to instantiate "org.apache.xerces.jaxp.validation.XMLSchemaFactory" (and probably fails finding it).

Why this difference ? What seems to be the problem, any ideea ?

Answer 1

This work for me on JRE 7:

SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = factory.newSchema(new SAXSource(new InputSource(new ByteArrayInputStream(xsd.getBytes()))));
Validator validator = schema.newValidator();

validator.validate(new SAXSource(new InputSource(new ByteArrayInputStream(xml.getBytes()))));
System.out.println("Validated !");

Answer 2

I got this to work by using the Thread Context Class Loader (often abbreviated TCCL). Here's the code:

ClassLoader original = Thread.currentThread().getContextClassLoader();
try {
  Thread.currentThread().setContextClassLoader(ClassWithinYourBundle.class.getClassLoader());
  SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
} finally {
  Thread.currentThread().setContextClassLoader(original);
}

Replacing ClassWithinYourBundle appropriately.

Here's a GitHub Project for further details.

For more information on TCCL, see: https://articles.qos.ch/classloader.html