JAXB @XmlElements，类型不同但名称相同？

要映射此用例，可以利用以下XmlAdapters：

动物适配器

由于AnimalExtension是Animal的超集，因此我们将使用它来生成/使用XML。然后，我们将利用animalId属性的值来确定是否将Animal或AnimalExtension的实例返回给AnimalList。

import javax.xml.bind.annotation.adapters.XmlAdapter;public class AnimalAdapter extends XmlAdapter<AnimalExtension, Animal> {    @Override    public Animal unmarshal(AnimalExtension animalExtension) throws Exception {        if(0 != animalExtension.getAnimalId()) { return animalExtension;        }        Animal animal = new Animal();        animal.setName(animalExtension.getName());        return animal;    }    @Override    public AnimalExtension marshal(Animal animal) throws Exception {        if(animal.getClass() == AnimalExtension.class) { return (AnimalExtension) animal;        }        AnimalExtension animalExtension = new AnimalExtension();        animalExtension.setName(animal.getName());        return animalExtension;    }}

IdAdapter

如果它的值为0，我们将需要第二个XmlAdapter来抑制animalId：

import javax.xml.bind.annotation.adapters.XmlAdapter;public class IdAdapter extends XmlAdapter<String, Integer> {    @Override    public Integer unmarshal(String string) throws Exception {        return Integer.valueOf(string);    }    @Override    public String marshal(Integer integer) throws Exception {        if(integer == 0) { return null;        }        return String.valueOf(integer);    }}

模型类的注释如下：

动物名单

import java.util.ArrayList;import java.util.List;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlRootElement;import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;@XmlRootElement(name="AnimalList")public class AnimalList {    private List<Animal> animalList = new ArrayList<Animal>();    @XmlElement(name="Animal")    @XmlJavaTypeAdapter(AnimalAdapter.class)    public List<Animal> getEntries() {        return animalList;    }}

动物

import javax.xml.bind.annotation.XmlAttribute;public class Animal {    private String name;    @XmlAttribute    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

动物延伸

import javax.xml.bind.annotation.XmlAttribute;import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;public class AnimalExtension extends Animal {    private int animalId;    @XmlAttribute(name="id")    @XmlJavaTypeAdapter(IdAdapter.class)    public int getAnimalId() {        return animalId;    }    public void setAnimalId(int animalId) {        this.animalId = animalId;    }}

示范代码

以下演示代码可用于演示此解决方案：

import java.io.File;import javax.xml.bind.JAXBContext;import javax.xml.bind.Marshaller;import javax.xml.bind.Unmarshaller;public class Demo {    public static void main(String[] args) throws Exception {        JAXBContext jc = JAXBContext.newInstance(AnimalList.class);        Unmarshaller unmarshaller = jc.createUnmarshaller();        File xml = new File("input.xml");        AnimalList animalList = (AnimalList) unmarshaller.unmarshal(xml);        for(Animal animal : animalList.getEntries()) { System.out.println(animal.getClass());        }        Marshaller marshaller = jc.createMarshaller();        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);        marshaller.marshal(animalList, System.out);    }}

将产生以下输出：

class AnimalExtensionclass Animal<?xml version="1.0" encoding="UTF-8"?><AnimalList xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">   <Animal name="Don" id="1"/>   <Animal name="Mike"/></AnimalList>

相关信息

您可能会发现以下信息有用：

• http://bdoughan.blogspot.com/2010/07/xmladapter-jaxbs-secret-weapon.html
• http://bdoughan.blogspot.com/2010/07/xmladapter-jaxbs-secret-weapon.html
• http://bdoughan.blogspot.com/2010/11/jaxb-and-inheritance-using-substitution.html