MOXy反序列化异常：在项目中找不到带有默认根元素的描述符

以下是我对您的两个问题的回答：

问题＃1-例外

当使用该

MarshallerProperties.JSON_INCLUDE_ROOT

unmarshal

Class

StreamSource json = new StreamSource("src/forum14246033/input.json");Zoo zoo = unmarshaller.unmarshal(json, Zoo.class).getValue();

问题2

还有一个关于序列化JSON的问题：是否有一种方法可以使JSON序列化程序发布“ @type”而不是“
type”。当前，它看起来像具有属性“类型”的对象。如果我们可以用“ @”修饰它，那么显然这更多的是类型信息而不是属性。

该

@

JAXBContextProperties.JSON_ATTRIBUTE_PREFIX

properties.put(JAXBContextProperties.JSON_ATTRIBUTE_PREFIX, "@");

完整的例子

演示版

package forum14246033;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>(2);        properties.put(JAXBContextProperties.MEDIA_TYPE, "application/json");        properties.put(JAXBContextProperties.JSON_INCLUDE_ROOT, false);        properties.put(JAXBContextProperties.JSON_ATTRIBUTE_PREFIX, "@");        JAXBContext jc = JAXBContext.newInstance(new Class[] {Zoo.class}, properties);        Unmarshaller unmarshaller = jc.createUnmarshaller();        StreamSource json = new StreamSource("src/forum14246033/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);    }}

input.json /输出

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

领域模型

我不建议在域模型中使用公共字段，但是如果您这样做，则可以将元数据缩减为以下内容：

动物园

import java.util.Collection;class Zoo {    public Collection<? extends Animal> animals;}

动物

import javax.xml.bind.annotation.XmlSeeAlso;import org.eclipse.persistence.oxm.annotations.XmlDiscriminatorNode;@XmlSeeAlso({Bird.class, Cat.class, Dog.class})@XmlDiscriminatorNode("@type")abstract class Animal {    public String name;}

鸟

import org.eclipse.persistence.oxm.annotations.XmlDiscriminatorValue;@XmlDiscriminatorValue("Bird")class Bird extends Animal {    public String wingSpan;    public String preferredFood;}

jaxb.properties

要将MOXy指定为JAXB（JSR-222）提供程序，您需要

jaxb.properties

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory