class Zoo {
public Collection<? extends Animal> animals;
}
当与MOXy序列化时,我得到：
{
"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"
}
]
}
为什么使用数组指示符“[]”,而鸟,猫和狗不是数组？
第二,有没有办法摆脱“鸟”,“猫”和“狗”？
换句话说,我试图去：
{
{
"name": "bird-1","preferredFood": "food-1"
},{
"name": "cat-1","favoritetoy": "toy-1"
},{
"name": "dog-1","leashColor": "black"
}
}
谢谢,
Behzad
解决方法
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);
}
}