我正在寻找一个可以根据JSPON specification.
处理引用的Java JSPON序列化程序目前有没有可以做到的？或者有没有办法修改现有的序列化程序来处理带有$ ref表示法的对象引用？
答案 0 :(得分：0)
我会使用众多Object to JSon序列化库中的一个。许多库都是可扩展的，但我怀疑添加引用可能会变得复杂，除非你在何时使用它们做出一些实用的选择。
答案 1 :(得分：0)
注意：我是EclipseLink JAXB (MOXy)主管，是JAXB 2 (JSR-222)专家组的成员。
如果您对object-JSON绑定方法感兴趣，下面是使用MOXy完成的方法。以下示例基于JSPON Core Spec中的示例：
<强>父
Parent类是与JSON消息的根对应的域对象。它有两个类型为Child的字段。
package forum9862100;
import javax.xml.bind.annotation.*;
@XmlAccessorType(XmlAccessType.FIELD)
public class Parent {
protected Child field1;
protected Child field2;
}
儿童
Child类可以通过其键引用。我们将使用XmlAdapter处理此用例。我们通过XmlAdapter注释链接到@XmlJavaTypeAdapter。
package forum9862100;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
@XmlJavaTypeAdapter(ChildAdapter.class)
@XmlAccessorType(XmlAccessType.FIELD)
public class Child {
protected String id;
protected String foo;
protected Integer bar;
}
<强> ChildAdapter
以下是XmlAdapter的实施。此XmlAdapter是有状态的，这意味着我们需要在Marshaller和Unmarshaller上设置实例。
package forum9862100;
import java.util.*;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.adapters.XmlAdapter;
public class ChildAdapter extends XmlAdapter<ChildAdapter.AdaptedChild, Child>{
private List<Child> childList = new ArrayList<Child>();
private Map<String, Child> childMap = new HashMap<String, Child>();
public static class AdaptedChild extends Child {
@XmlElement(name="$ref")
public String reference;
}
@Override
public AdaptedChild marshal(Child child) throws Exception {
AdaptedChild adaptedChild = new AdaptedChild();
if(childList.contains(child)) {
adaptedChild.reference = child.id;
} else {
adaptedChild.id = child.id;
adaptedChild.foo = child.foo;
adaptedChild.bar = child.bar;
childList.add(child);
}
return adaptedChild;
}
@Override
public Child unmarshal(AdaptedChild adaptedChild) throws Exception {
Child child = childMap.get(adaptedChild.reference);
if(null == child) {
child = new Child();
child.id = adaptedChild.id;
child.foo = adaptedChild.foo;
child.bar = adaptedChild.bar;
childMap.put(child.id, child);
}
return child;
}
}
<强>演示
以下代码演示了如何在XmlAdapter和Marshaller上指定有状态Unmarshaller：
package forum9862100;
import java.io.File;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Parent.class);
StreamSource json = new StreamSource(new File("src/forum9862100/input.json"));
Unmarshaller unmarshaller = jc.createUnmarshaller();
unmarshaller.setProperty("eclipselink.media-type", "application/json");
unmarshaller.setProperty("eclipselink.json.include-root", false);
unmarshaller.setAdapter(new ChildAdapter());
Parent parent = (Parent) unmarshaller.unmarshal(json, Parent.class).getValue();
System.out.println(parent.field1 == parent.field2);
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty("eclipselink.media-type", "application/json");
marshaller.setProperty("eclipselink.json.include-root", false);
marshaller.setAdapter(new ChildAdapter());
marshaller.marshal(parent, System.out);
}
}
<强>输出
以下是运行演示代码的输出。请注意Child的两个实例如何通过身份测试。
true
{
"field1" : {
"id" : "2",
"foo" : "val",
"bar" : 4
},
"field2" : {
"$ref" : "2"
}}
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