JAXB-具有多个名称和类型的XmlElement [英] JAXB - XmlElement with multiple names and types

问题描述

我具有以下类层次结构:

I have the following class hierarchy:

@XmlRootElement
public abstract class Animal{}

@XmlRootElement
public class Dog extends Animal{}

@XmlRootElement
public class Cat extends Animal{}

@XmlRootElement
public class Lion extends Animal{}

和一个具有名为animal的属性的类:

and a class which has an attribute named animal:

@XmlRootElement
public class Owner{
  private Animal animal;
}

我想允许以下不同的XML模式，并将模式中的Animal Type绑定到Owner class

I would like to allow different XML Schemas as follows and bind the Animal Type in the schema to animal object in Owner class

<Owner>
 <Dog></Dog>
</Owner>

<Owner>
 <Cat></Cat>
</Owner>

<Owner>
 <Lion></Lion>
</Owner>

我发现的解决方案使用XmlElements，它可以采用多个XmlElement字段并创建一个集合.但是，就我而言，我不需要一个集合，而只需一个属性.

The solutions that I have found use XmlElements which can take multiple XmlElement fields and creates a collection. However, in my case I don't need a collection but a single attribute.

JAXB是否为此问题允许任何XmlElement多重命名约定? 还有其他注释可以解决此问题吗?

Does JAXB allow any XmlElement multiple naming convention for this problem? Is there any other annotation which could solve this problem?

注意:我已经在stackoverflow及其周围查看了多个类似问题的答案，但几乎所有答案都创建了一个集合，而不是一个对象.我找到的最接近的答案是: @具有多个名称的XmlElement

Note: I have looked at multiple answers to similar questions in stackoverflow and around but almost all of them create a collection instead of a single object. The closest answer I have found is this : @XmlElement with multiple names

我认为此解决方案可能会起作用.必须进行测试

Edit : I think this solution might work. Have to test it out

推荐答案

我使用

I got it to work using the @XmlElements annotation, as follows:

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import java.io.ByteArrayInputStream;
import java.nio.charset.StandardCharsets;

public class Main {
    public static void main(String[] args) throws JAXBException {
        String xml = "<owner><dog></dog></owner>";
        JAXBContext jaxbContext = JAXBContext.newInstance(Owner.class);
        Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
        Owner owner = (Owner) jaxbUnmarshaller.unmarshal(
                new ByteArrayInputStream(xml.getBytes(StandardCharsets.UTF_8)));

        System.out.println(owner.getAnimal().getClass());
    }
}

abstract class Animal {}

class Dog extends Animal {}

class Cat extends Animal {}

class Lion extends Animal {}

@XmlRootElement
class Owner {
    @XmlElements({
            @XmlElement(name = "dog", type = Dog.class),
            @XmlElement(name = "cat", type = Cat.class),
            @XmlElement(name = "lion", type = Lion.class)
    })
    private Animal animal;

    public Animal getAnimal() {
        return animal;
    }
}

使用Oracle Java 8 SDK附带的默认JAXB实现，输出如下:

Using the default JAXB implementation that ships with the Oracle Java 8 SDK, this prints out:

class Dog

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