Java 使用 JaxB 编组实现公共接口的对象列表
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Marshalling a List of objects implementing a common interface, with JaxB
提问by Beni
I am trying to marshall a list of objects implementing a common interface. There are 3 classes and 1 interface involved:
我正在尝试编组实现通用接口的对象列表。涉及3个类和1个接口：
Communityclass (has one method: List<Person> getPeople();)
社区类（有一个方法：List<Person> getPeople();）
Personinterface (has one method: String getName();)
Person接口（有一个方法：String getName();）
Girlclass (implements Person)
Girl类（实现 Person）
Boyclass (implements Person)
男孩类（实现人）
See code below.
请参阅下面的代码。
I want an XML that looks something like this:
我想要一个看起来像这样的 XML：
<community>
<people>
<girl>
<name>Jane</name>
</girl>
<boy>
<name>John</name>
</boy>
<girl>
<name>Jane</name>
</girl>
<boy>
<name>John</name>
</boy>
</people>
</community>
or possibly:
或者可能：
<community>
<people>
<person>
<girl>
<name>Jane</name>
</girl>
</person>
<person>
<boy>
<name>John</name>
</boy>
</person>
</people>
</community>
So far what I get is this:
到目前为止，我得到的是：
<community>
<people>
<person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="girl">
<name>Jane</name>
</person>
<person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="boy">
<name>John</name>
</person>
<person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="girl">
<name>Jane</name>
</person>
<person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="boy">
<name>John</name>
</person>
</people>
</community>
I realize I can change the element to something else, but I want the element name to be the name spesified in the Girl or Boy class.
我意识到我可以将元素更改为其他内容，但我希望元素名称是在 Girl 或 Boy 类中指定的名称。
Can this be done? Thanks.
这能做到吗？谢谢。
@XmlRootElement(name = "community")
public class Community {
private List<Person> people;
@XmlElementWrapper
@XmlElement(name="person")
public List<Person> getPeople() {
return people;
}
public Community() {
people = new ArrayList<Person>();
people.add(new Girl());
people.add(new Boy());
people.add(new Girl());
people.add(new Boy());
}
}
@XmlRootElement(name = "girl")
public class Girl implements Person {
@XmlElement
public String getName() {
return "Jane";
}
}
@XmlRootElement(name = "boy")
public class Boy implements Person {
@XmlElement
public String getName() {
return "John";
}
}
@XmlJavaTypeAdapter(AnyTypeAdapter.class)
public interface Person {
public String getName();
}
public class AnyTypeAdapter extends XmlAdapter<Object, Object> {
@Override
public Object marshal(Object v) throws Exception {
return v;
}
@Override
public Object unmarshal(Object v) throws Exception {
return v;
}
}
采纳答案by bdoughan
For this scenario I would recommend the use of @XmlElements. @XmlElements is used to represent the XML schema concept of choice:
对于这种情况，我建议使用@XmlElements。@XmlElements 用于表示选择的 XML 模式概念：
Here is how it would look for your example:
以下是它如何查找您的示例：
@XmlElements({
@XmlElement(name="girl", type=Girl.class),
@XmlElement(name="boy", type=Boy.class)
})
@XmlElementWrapper
public List<Person> getPeople() {
return people;
}
@XmlElementRef corresponds to the concept of substitution groups in XML schema. This is why the previous answer requires Person to be changed from an interface to a class.
@XmlElementRef 对应于 XML 模式中替换组的概念。这就是为什么之前的答案要求将 Person 从接口更改为类的原因。
回答by Gary Rowe
OK, if you're prepared to change Person from an interface into an abstract base class, then you're golden. Here's the code:
好的，如果您准备将 Person 从接口更改为抽象基类，那么您就是金子。这是代码：
public class Main {
public static void main(String[] args) throws Exception {
Community community = new Community();
JAXBContext context = JAXBContext.newInstance(Community.class);
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(community, System.out);
}
}
@XmlRootElement(name = "community")
@XmlSeeAlso({Person.class})
public class Community {
private List<Person> people;
@XmlElementWrapper(name="people")
@XmlElementRef()
public List<Person> getPeople() {
return people;
}
public Community() {
people = new ArrayList<Person>();
people.add(new Girl());
people.add(new Boy());
people.add(new Girl());
people.add(new Boy());
}
}
@XmlRootElement(name="boy")
public class Boy extends Person {
public String getName() {
return "John";
}
}
@XmlRootElement(name="girl")
public class Girl extends Person {
public String getName() {
return "Jane";
}
}
@XmlRootElement(name = "person")
@XmlSeeAlso({Girl.class,Boy.class})
public abstract class Person {
@XmlElement(name="name")
public abstract String getName();
}
The main trick was the use of @XmlElementRefin the List of Community. This identifies the type of the class through it's @XmlRootElement. You may also be interested in the @XmlSeeAlsowhich helps to organise context declarations.
主要技巧是在社区列表中使用@XmlElementRef。这通过它的@XmlRootElement 标识类的类型。您可能还对有助于组织上下文声明的@XmlSeeAlso感兴趣。
And the output is
输出是
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<community>
<people>
<girl>
<name>Jane</name>
</girl>
<boy>
<name>John</name>
</boy>
<girl>
<name>Jane</name>
</girl>
<boy>
<name>John</name>
</boy>
</people>
</community>
