使用JAXB解组由子类组成的XML文件

Question

我有一个超级＆＃39;车辆＆＃39;如下所示，它提供了一系列子类的核心信息，其中一个子类是“Car＆＃39;也显示如下。

package transport;

public abstract class RoadVehicle
{
    public enum FuelType
    {
        ELECTRIC, PETROL, DIESEL
    }

    private final FuelType fuelType;
    private String licencePlateRegistration;
    private int ownerId;
    private final short yearManufactured;
    private final boolean isAutomatic;
    private static int numberOfVehicles = 0;


    public RoadVehicle(FuelType fuelType, String licencePlateRegistration, int ownerId, short yearManufactured, boolean isAutomatic)
    {
        this.fuelType = fuelType;
        this.licencePlateRegistration = licencePlateRegistration;
        this.ownerId = ownerId;
        this.yearManufactured = yearManufactured;
        this.isAutomatic = isAutomatic;
        numberOfVehicles ++;
    }

    public FuelType getFuelType()
    {
        return this.fuelType;
    }

    public short getYearManufactured()
    {
        return this.yearManufactured;
    }

    public boolean getIsAutomatic()
    {
        return this.isAutomatic;
    }

    public void setLicencePlateNumber(String licencePlateNumber)
    {
        this.licencePlateRegistration = licencePlateNumber;
    }

    public String getLicencePlateNumber()
    {
        return this.licencePlateRegistration;
    }

    public void setOwnerId(int ownerId)
    {
        this.ownerId = ownerId;
    }

    public int getOwnerId()
    {
        return this.ownerId;
    }

    public int getNumberOfVehicles()
    {
        return RoadVehicle.numberOfVehicles;
    }
}

汽车课

package transport;

public class Car extends RoadVehicle
{
    private final short engineSizeInCC;
    private static int numberOfCars = 0;

    public Car(FuelType fuelType, String licencePlateRegistration, int ownerId, short yearManufactured, boolean isAutomatic, short engineSizeInCC)
    {
        super(fuelType, licencePlateRegistration, ownerId, yearManufactured, isAutomatic);
        this.engineSizeInCC = engineSizeInCC;
        numberOfCars ++;
    }

    public short getEngineSizeInCC()
    {
        return this.engineSizeInCC;
    }

    public int getNumberOfCars()
    {
        return Car.numberOfCars;
    }
}

使用JaxB教程我试图提供一个XML文件（现在只包含一个汽车），以便应用程序使用以下类创建Java对象

package transport;

import java.io.File;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;

public class XMLParser
{
    public static void main(String[] args)
    {
        try
        {
            JAXBContext jaxbContext = JAXBContext.newInstance(Car.class);

            Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();

            File XMLfile = new File("C:\\home\\XML.xml");

            Car car = (Car) jaxbUnmarshaller.unmarshal(XMLfile);

            System.out.println("CAR " +car.getLicencePlateNumber());
        }
        catch (JAXBException e)
        {
            e.printStackTrace();
        }
    }
}

当我运行此命令时，我收到以下错误消息：

com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 2 counts of IllegalAnnotationExceptions
transport.Car does not have a no-arg default constructor.
    this problem is related to the following location:
        at transport.Car
transport.RoadVehicle does not have a no-arg default constructor.
    this problem is related to the following location:
        at transport.RoadVehicle
        at transport.Car

    at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:436)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:277)
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1100)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:143)
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:110)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:202)
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:376)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:574)
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:522)
    at transport.XMLParser.main(XMLParser.java:15)

考虑到XML解析器类只创建一个Car对象，我会走在正确的道路上，而我需要解析器来解释XML应该转换为什么类型的对象，即van，car，lorry？