使用JAXB编组/解组Java超类和子类 [英] Marshalling/Unmarshalling Java superclass and subclasses using JAXB
问题描述
我一直在试验JAXB教程，并设法让代码工作，从Java对象生成XML文件，然后能够使用XML生成Java对象。目前它读取同一类的多个实例以创建类似于下面的XML文件
I've been experimenting with JAXB tutorials and have managed to get code working that generates an XML file from a Java object and then is able to use the XML to generate a Java object. At the moment it reads multiple instances of the same class to create an XML file similar to the one below
<Car>
<regplate>TR54</regplate>
<colour>red</colour>
<energyrating>5</energyrating>
</Car>
<Car>
<regplate>BN04 THY</regplate>
<colour>yellow</colour>
<energyrating>3</energyrating>
</Car>
<Car>
<regplate>BN05 THY</regplate>
<colour>yellow</colour>
<energyrating>5</energyrating>
</Car>
我希望能够使用JAXB技术来处理子类。例如：假设我有一个Car，Van和Bicycle对象，它们是Vehicle的子类。我是否可以操作我的JAXB类来编写一个可以产生类似内容的XML文件？我已经提供了我正在使用的代码。
I would like to be able to use the JAXB technology to work with subclasses. For example: Say I have a Car, Van and Bicycle objects that are subclasses of Vehicle. Is it possible for me to manipulate my JAXB class to write an XML file that would produce something similar to this? I have provided the code I am working with below.
<Vehicle>
<Car>
<regplate>TR54</regplate>
<colour>red</colour>
<energyrating>5</energyrating>
</Car>
<Van>
<regplate>MN05 RFD</regplate>
<colour>red</colour>
<energyrating>5</energyrating>
</Van>
<Car>
<regplate>ZX54 UJK</regplate>
<colour>red</colour>
<energyrating>1</energyrating>
</Car>
</Vehicle>
主要类别
package basictransport2;
public class Main
{
public static void main(String[] args)
{
JAXB parser = new JAXB();
parser.marshall();
//parser.unmarshallList();
}
}
车辆等级
package basictransport2;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
//@XmlRootElement(name = "Vehicle")
public class Vehicle
{
private int ownerId;
public Vehicle(int ownerId)
{
this.setOwnerId(ownerId);
}
//@XmlElement (name = "Owner ID")
public int getOwnerId()
{
return ownerId;
}
public void setOwnerId(int ownerId)
{
this.ownerId = ownerId;
}
public int getEnergyRating()
{
return (Integer) null;
}
public String getColour()
{
return null;
}
public String getRegPlate()
{
return null;
}
}
汽车等级
package basictransport2;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
//@XmlRootElement(name = "Car")
public class Car extends Vehicle
{
private String regPlate;
private int energyRating;
private String colour;
public Car(String regPlate, int energyRating, String colour, int ownerId)
{
super(ownerId);
this.regPlate = regPlate;
this.energyRating = energyRating;
this.colour = colour;
}
public Car(int ownerId)
{
super(ownerId);
}
//@XmlElement (name = "Registration")
public String getRegPlate()
{
return regPlate;
}
public void setRegPlate(String regPlate)
{
if(this.regPlate == null)
{
this.regPlate = regPlate;
}
}
//@XmlElement (name = "Energy Rating")
public int getEnergyRating()
{
return energyRating;
}
public void setEnergyRating(int energyRating)
{
this.energyRating = energyRating;
}
//@XmlElement (name = "Colour")
public String getColour()
{
return colour;
}
public void setColour(String colour)
{
this.colour = colour;
}
}
JAXB Class
JAXB Class
package basictransport2;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
public class JAXB
{
public void marshall()
{
try
{
List<Vehicle> vehicleList = new ArrayList<Vehicle>();
vehicleList.add(new Car("SG09 TYH", 4, "Yellow", 1));
vehicleList.add(new Car("XX09 VVV", 3, "Red", 2));
vehicleList.add(new Car("BL09 TYZ", 4, "Blue", 3));
Garage listOfVehicles = new Garage();
listOfVehicles.setListOfVehicles(vehicleList);
JAXBContext context = JAXBContext.newInstance(Garage.class);
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(listOfVehicles, System.out);
marshaller.marshal(listOfVehicles, new File("src\\data\\listcar.xml"));
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
public void unmarshall()
{
try
{
JAXBContext context = JAXBContext.newInstance(Garage.class);
Unmarshaller unmarhsaller = context.createUnmarshaller();
Garage listOfVehicles = (Garage)unmarhsaller.unmarshal(new File("src\\data\\listcar.xml"));
System.out.println("List Car information");
for(Vehicle vehicle : listOfVehicles.getListOfVehicles())
{
System.out.println("Reg Plate: " + vehicle.getRegPlate());
System.out.println("Energy Rating: " + vehicle.getEnergyRating());
System.out.println("Colour: " + vehicle.getColour());
System.out.println("================");
}
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
}
}
列表类
package basictransport2;
import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlSeeAlso;
import javax.xml.bind.annotation.XmlType;
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name="Vehicle")
public class Garage
{
@XmlElements
({
@XmlElement(name = "Car", type = Car.class, required = false)
})
private List<Vehicle> vehicleCollection = new ArrayList<Vehicle>();
public List<Vehicle> getListOfVehicles()
{
return vehicleCollection;
}
public void setListOfVehicles(List<Vehicle> listOfVehicles)
{
this.vehicleCollection = listOfVehicles;
}
}
推荐答案
谢谢每个人都为你的意见。我使用了你所有答案的反馈，但最终它们的组合才有效，这就是为什么我为将来可能遇到这个问题的人创建了一个单独的答案。
Thanks everyone for your input. I used feedback from all your answers but ultimately it was a combination of them that worked which is why I created a seperate answer for anyone who may have this problem in the future.
为了实现这一点，我必须确保使用 @XmlElement 注释超级和子类中的所有getter方法是marhsalled / unmarshalled。这将确定相应变量的XML标记。
To get this to work I had to ensure that all getter methods within the super and sub classes being marhsalled/unmarshalled were annotated with @XmlElement. This would determine the XML tag for the corresponding variable.
@XmlElement (name = "OwnerID")
public int getOwnerId()
{
return ownerId;
}
超类必须使用 @XmlSeeAlso <进行注释/ code>将子类绑定到它。即在我的代码 RoadVehicle 是超类，并且 Car 和 Van 类扩展了它。
The superclass had to be annotated with @XmlSeeAlso to bind the subclasses to it. i.e In my code RoadVehicle was the superclass and both the Car and Van classes extended it.
@XmlSeeAlso({Car.class, Van.class})
public class Vehicle
{
现在，超级和子类被注释，唯一需要注释的其他类是列表类（我的代码中的Garage）。此处的更改将确定填充XML标记的内容。
With the super and subclasses now annotated the only other class that required annotations was the list class (Garage in my code). The changes here would determine what the XML tags were populated with.
通过应用 @XmlRootElement 注释到班级的顶部。即Vehicle将是我示例中的根XML标记。
The root XML tag was set by applying the @XmlRootElement annotation to the top of the class. i.e. "Vehicle" would be the root XML tag in my example.
@XmlRootElement(name = "Vehicle")
public class Garage
{
最后一个 @XmlElements list必须使用 @XmlElements 注释声明每个需要带有 name 提供XML标记的名称。此列表必须在集合的getter方法上方声明。
Finally an @XmlElements list had to be declared with an @XmlElements annotation for each sub class that required an XML tag with the name supplying the name of the XML tag. This list had to be declared above the getter method for the collection.
@XmlElements
({
@XmlElement(name = "Car", type = Car.class, required = false),
@XmlElement(name = "Van", type = Van.class, required = false)
})
public List<Vehicle> getListOfVehicles()
{
return vehicleCollection;
}
这篇关于使用JAXB编组/解组Java超类和子类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
