json - 从 json 解码嵌套对象

Question

我有传入的 JSON 字符串，我需要解码为 JAXB 注释对象。我正在使用 jettison 来做到这一点。 JSON 字符串如下所示:

{ 
  objectA : 
  { 
    "propertyOne" : "some val", 
    "propertyTwo" : "some other val",
    objectB : 
    {
      "propertyA" : "some val",
      "propertyB" : "true" 
    }
  }
}

ObjectA 代码如下所示:

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "objectA")
public class ObjectA {
    @XmlElement(required = true)
    protected String propertyOne;
    @XmlElement(required = true)
    protected String propertyTwo;
    @XmlElement(required = true)
    protected ObjectB objectB;
}

ObjectB 类代码如下所示:

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "objectB")
public class ObjectB {
    @XmlElement(required = true)
    protected String propertyA;
    @XmlElement(required = true)
    protected boolean propertyB;
}

用于解码的代码:

JAXBContext jc = JAXBContext.newInstance(OnjectA.class);
JSONObject obj = new JSONObject(theJsonString);
Configuration config = new Configuration();

MappedNamespaceConvention con = new MappedNamespaceConvention(config);
XMLStreamReader xmlStreamReader = new MappedXMLStreamReader(obj,con);
Unmarshaller unmarshaller = jc.createUnmarshaller();

ObjectA obj = (ObjectA) unmarshaller.unmarshal(xmlStreamReader);

它不会抛出任何异常或警告。发生的情况是 ObjectB 已实例化，但其属性均未设置值，即 propertyA 为 null，而 propertyB 的默认值为 false。我一直在努力弄清楚为什么这不起作用。有人可以帮忙吗？

Answer 1

注意:我是 EclipseLink JAXB (MOXy) JAXB (JSR-222) 的领导和成员专家组。

您模型上的 JAXB 映射似乎是正确的。下面是示例代码，其中我使用了您在问题中给出的确切模型以及通过 EclipseLink MOXy 提供的 JSON 绑定(bind):

演示

package forum16365788;

import java.io.File;
import java.util.*;
import javax.xml.bind.*;
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>(1);
        properties.put(JAXBContextProperties.MEDIA_TYPE, "application/json");
        JAXBContext jc = JAXBContext.newInstance(new Class[] {ObjectA.class}, properties);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File json = new File("src/forum16365788/input.json");
        ObjectA objectA = (ObjectA) unmarshaller.unmarshal(json);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(objectA, System.out);
    }

}

input.json/输出

下面是我使用的 JSON。键 objectA 和 objectB 应该被引用，你的问题中没有这个。

{
   "objectA" : {
      "propertyOne" : "some val",
      "propertyTwo" : "some other val",
      "objectB" : {
         "propertyA" : "some val",
         "propertyB" : true
      }
   }
}

了解更多信息

• http://blog.bdoughan.com/2011/08/json-binding-with-eclipselink-moxy.html
• http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html