How to validate against schema in JAXB 2.0 without marshalling?

Firstly, javax.xml.bind.Validator has been deprecated in favour of javax.xml.validation.Schema (javadoc). The idea is that you parse your schema via a javax.xml.validation.SchemaFactory (javadoc), and inject that into the marshaller/unmarshaller.

As for your question regarding validation without marshalling, the problem here is that JAXB actually delegates the validation to Xerces (or whichever SAX processor you're using), and Xerces validates your document as a stream of SAX events. So in order to validate, you need to perform some kind of marshalling.

The lowest-impact implementation of this would be to use a "/dev/null" implementation of a SAX processor. Marshalling to a null OutputStream would still involve XML generation, which is wasteful. So I would suggest:

SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = schemaFactory.newSchema(locationOfMySchema); 

Marshaller marshaller = jaxbContext.createMarshaller();
marshaller.setSchema(schema);
marshaller.marshal(objectToMarshal, new DefaultHandler());

DefaultHandler will discard all the events, and the marshal() operation will throw a JAXBException if validation against the schema fails.

You could use a javax.xml.bind.util.JAXBSource (javadoc) and a javax.xml.validation.Validator (javadoc), throw in an implementation of org.xml.sax.ErrorHandler (javadoc) and do the following:

import java.io.File;

import javax.xml.XMLConstants;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.util.JAXBSource;
import javax.xml.validation.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        Customer customer = new Customer();
        customer.setName("Jane Doe");
        customer.getPhoneNumbers().add(new PhoneNumber());
        customer.getPhoneNumbers().add(new PhoneNumber());
        customer.getPhoneNumbers().add(new PhoneNumber());

        JAXBContext jc = JAXBContext.newInstance(Customer.class);
        JAXBSource source = new JAXBSource(jc, customer);

        SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI); 
        Schema schema = sf.newSchema(new File("customer.xsd")); 

        Validator validator = schema.newValidator();
        validator.setErrorHandler(new MyErrorHandler());
        validator.validate(source);
    }

}

For More Information, See My Blog

• http://blog.bdoughan.com/2010/11/validate-jaxb-object-model-with-xml.html