Solution of * doesnt contain ObjectFactory.class or jaxb.index
For some reason while unmarshalling something you get this error
Solution is:
Instead of
javax.xml.bind.JAXBContext jaxbCtx = javax.xml.bind.JAXBContext.newInstance("oasis.names.specification.ubl.schema.xsd.invoice_2");
or
JAXBContext context = JAXBContext.newInstance(inv.getClass().getPackage().getName());
Use a notation like this
javax.xml.bind.JAXBContext jaxbCtx = javax.xml.bind.JAXBContext.newInstance(oasis.names.specification.ubl.schema.xsd.invoice_2.InvoiceType.class);
Where InvoiceType will be the thing you want to unmarshall into

you can try this:
javax.xml.bind.JAXBContext jaxbCtx = javax.xml.bind.JAXBContext.newInstance("oasis.names.specification.ubl.schema.xsd.invoice_2", getClass().getClassLoader());
I think problem in ClassLoader.