Let's consider the code below:

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBContextFactory;
import javax.xml.bind.JAXBException;
import java.util.Map;

public class Test3 {
    public static class Factory implements JAXBContextFactory {
        @Override
        public JAXBContext createContext(Class<?>[] classesToBeBound, Map<String, ?> properties) throws JAXBException {
            throw new Error();
        }

        @Override
        public JAXBContext createContext(String contextPath, ClassLoader classLoader, Map<String, ?> properties)
                throws JAXBException {
            throw new Error();
        }
    }
    public static void main(String[] args) throws JAXBException {
        System.setProperty(JAXBContext.JAXB_CONTEXT_FACTORY, "Test3$Factory");
        try {
            JAXBContext.newInstance(Test3.class);
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }
}

This code produces following stack trace when being run on JDKb94:

java.lang.NullPointerException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:520)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:258)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:249)
at javax.xml.bind.ContextFinder.find(ContextFinder.java:355)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:662)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:606)
at Test3.main(Test3.java:29)