Below are my answers to your two questions:
Question #1 - Exception
When you use the MarshallerProperties.JSON_INCLUDE_ROOT property to turn off root elements then you need to use one of the unmarshal methods that takes a Class parameter to tell MOXy the type of object you wish to unmarshal.
StreamSource json = new StreamSource("src/forum14246033/input.json");
Zoo zoo = unmarshaller.unmarshal(json, Zoo.class).getValue();
Question #2
Also a question on the serialized JSON: Is there a way to get the JSON
serializer to publish "@type" instead of "type". Currently, it looks
like the objects having the property "type". If we could decorate it
with "@", it will be more obvious that this is more of a type info
than a property.
The @ prefix indicates that a field/property maps to an XML attribute. You can use the JAXBContextProperties.JSON_ATTRIBUTE_PREFIX property to specify a prefix to qualify data that was mapped to an XML attribute.
properties.put(JAXBContextProperties.JSON_ATTRIBUTE_PREFIX, "@");
FULL EXAMPLE
Demo
package forum14246033;
import java.util.*;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;
import org.eclipse.persistence.jaxb.JAXBContextProperties;
public class Demo {
public static void main(String[] args) throws Exception {
Map<String, Object> properties = new HashMap<String, Object>(2);
properties.put(JAXBContextProperties.MEDIA_TYPE, "application/json");
properties.put(JAXBContextProperties.JSON_INCLUDE_ROOT, false);
properties.put(JAXBContextProperties.JSON_ATTRIBUTE_PREFIX, "@");
JAXBContext jc = JAXBContext.newInstance(new Class[] {Zoo.class}, properties);
Unmarshaller unmarshaller = jc.createUnmarshaller();
StreamSource json = new StreamSource("src/forum14246033/input.json");
Zoo zoo = unmarshaller.unmarshal(json, Zoo.class).getValue();
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(zoo, System.out);
}
}
input.json/Output
{
"animals" : [ {
"@type" : "Bird",
"name" : "bird-1",
"wingSpan" : "6 feets",
"preferredFood" : "food-1"
}, {
"@type" : "Cat",
"name" : "cat-1",
"favoriteToy" : "toy-1"
}, {
"@type" : "Dog",
"name" : "dog-1",
"breed" : "bread-1",
"leashColor" : "black"
} ]
}
DOMAIN MODEL
I don't recommend using public fields in your domain model, but if you go that way you can reduce your metadata down to the following:
Zoo
import java.util.Collection;
class Zoo {
public Collection<? extends Animal> animals;
}
Animal
import javax.xml.bind.annotation.XmlSeeAlso;
import org.eclipse.persistence.oxm.annotations.XmlDiscriminatorNode;
@XmlSeeAlso({Bird.class, Cat.class, Dog.class})
@XmlDiscriminatorNode("@type")
abstract class Animal {
public String name;
}
Bird
import org.eclipse.persistence.oxm.annotations.XmlDiscriminatorValue;
@XmlDiscriminatorValue("Bird")
class Bird extends Animal {
public String wingSpan;
public String preferredFood;
}
jaxb.properties
To specify MOXy as your JAXB (JSR-222) provider you need to include a file called jaxb.properties in the same package as your domain model with the following entry:
javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory
