Create an XSD to handle abstract types

Regarding jaxb abstract types, and the consumption of associated XML documents, an XML document cannot contain a reference to the abstract type - that is, the XML must use the concrete type.

Example (taken from here):

Invalid: < transport xmlns="http://cars.example.com/schema"/>

Valid: < transport xmlns="http://cars.example.com/schema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Car"/>

(where transport is abstract)

Q. How can i instruct Jaxb to unmarshall such that it includes / populates the "xsi:type" value appropriately?

Btw, all my jaxb classes are in then same package, and my JaxbContext is configured against this package.

---

You could do the following:

Car

The @XmlType annotation can be used to specify the type name.

import javax.xml.bind.annotation.XmlType;

@XmlType(name="Car")
public class Car {

}

Demo

Whenever the Java type for an XML element is Object then your JAXB implementation will qualify the element with the xsi:type attribute. Below we will leverage an instance of JAXBElement for this.

import javax.xml.bind.*;
import javax.xml.namespace.QName;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Car.class);

        Car car = new Car();
        JAXBElement<Object> jaxbElement = new JAXBElement(new QName("transport"), Object.class, car); 

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(jaxbElement, System.out);
    }

}

Output

Below is the output from running the demo code.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<transport xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Car"/>

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