java – EclipseLink MOXy JSON序列化

Why is it using array indicators “[]”,while bird,cat,and dog are
not arrays?

要获取此JSON表示,您已将模型映射到@XmlElementRef注释,该注释告诉JAXB使用@XmlRootElement注释的值作为继承指标.使用MOXy的JSON绑定这些成为关键.我们使这些键JSON值的值由于键不允许重复.

动物园

在你的模型中,你的动物字段/属性上有@XmlElementRef注释.

import java.util.Collection;
import javax.xml.bind.annotation.XmlElementRef;

class Zoo {
    @XmlElementRef
    public Collection<? extends Animal> animals;
}

动物

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlSeeAlso({Bird.class,Cat.class,Dog.class})
public abstract class Animal {

    private String name;

}

鸟

在每个子类上,都有一个@XmlRootElement注释.

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Bird extends Animal {

    private String wingSpan;
    private String preferredFood;

}

input.json /输出

{
   "bird" : [ {
      "name" : "bird-1","wingSpan" : "6 feets","preferredFood" : "food-1"
   } ],"cat" : [ {
      "name" : "cat-1","favoriteToy" : "toy-1"
   } ],"dog" : [ {
      "name" : "dog-1","breed" : "bread-1","leashColor" : "black"
   } ]
}

了解更多信息

> http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-substitution.html

问题#2

Second,is there a way to get rid of “bird”,“cat”,and “dog”?

您将需要某种继承指标来表示各种子类.

选项#1 – @ XmlDescriminatorNode / @ XmlDescriminatorValue

这里我使用MOXy的@ XmlDescriminatorNode / @ XmlDescriminatorValue注释.

动物园

import java.util.Collection;

class Zoo {
    public Collection<? extends Animal> animals;
}

动物

import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlDiscriminatorNode;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlSeeAlso({Bird.class,Dog.class})
@XmlDiscriminatorNode("@type")
public abstract class Animal {

    private String name;

}

鸟

import org.eclipse.persistence.oxm.annotations.XmlDiscriminatorValue;

@XmlDiscriminatorValue("bird")
public class Bird extends Animal {

    private String wingSpan;
    private String preferredFood;

}

input.json /输出

{
   "animals" : [ {
      "type" : "bird","name" : "bird-1","preferredFood" : "food-1"
   },{
      "type" : "cat","name" : "cat-1","favoriteToy" : "toy-1"
   },{
      "type" : "dog","name" : "dog-1","leashColor" : "black"
   } ]
}

了解更多信息

> http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-moxy-extension.html

选项#2 – @XmlClassExtractor

ClassExtractor(AnimalExtractor)

您可以编写一些基于JSON内容确定适当子类的代码.

import org.eclipse.persistence.descriptors.ClassExtractor;
import org.eclipse.persistence.sessions.*;

public class AnimalExtractor extends ClassExtractor {

    @Override
    public Class extractClassFromRow(Record record,Session session) {
        if(null != record.get("@wingSpan") || null != record.get("@preferredFood")) {
            return Bird.class;
        } else if(null != record.get("@favoriteToy")) {
            return Cat.class;
        } else {
            return Dog.class;
        }
    }

}

动物

@XmlClassExtractor注释用于指定ClassExtractor.

import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlClassExtractor;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlSeeAlso({Bird.class,Dog.class})
@XmlClassExtractor(AnimalExtractor.class)
public abstract class Animal {

    private String name;

}

鸟

由于MOXy如何处理@XmlElement和@XmlAttribute注释,您希望将ClassExtractor可用的任何数据都需要使用@XmlAttribute进行注释.

import javax.xml.bind.annotation.XmlAttribute;

public class Bird extends Animal {

    @XmlAttribute
    private String wingSpan;

    @XmlAttribute
    private String preferredFood;

}

input.json /输出

{
   "animals" : [ {
      "wingSpan" : "6 feets","preferredFood" : "food-1","name" : "bird-1"
   },{
      "favoriteToy" : "toy-1","name" : "cat-1"
   },{
      "breed" : "bread-1","leashColor" : "black","name" : "dog-1"
   } ]
}

了解更多信息

> http://blog.bdoughan.com/2012/02/jaxb-and-inheritance-eclipselink-moxy.html

演示代码

以下演示代码可用于上述两种映射.

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>();
        properties.put(JAXBContextProperties.MEDIA_TYPE,"application/json");
        properties.put(JAXBContextProperties.JSON_INCLUDE_ROOT,false);
        JAXBContext jc = JAXBContext.newInstance(new Class[] {Zoo.class},properties);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        StreamSource json = new StreamSource("src/forum14210676/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);
    }

}