如何使用 JAXB 解组重复的嵌套类? [英] How to unmarshall repeated nested classes with JAXB?

问题描述

我如何指示 JAXB 处理这个?

How can I instruct JAXB to process this ?

XML

<root>
 <parent>
    <child id="1" name="foo" />
 </parent>
 <parent>
    <child id="3" name="foo2" />
 </parent>
 <parent>
    <child id="4" name="bar2" />
 </parent>
 <parent>
    <child id="2" name="bar" />
 </parent>
</root>

Root.java

@XmlRootElement
public class Root {
   @XmlElement(name="parent/child")
   List<Child> allChildren;
}

这不起作用...... allChildren 是空的.

This doesn't work ... allChildren is empty.

推荐答案

您可以更改模型并执行以下操作:

You could change your model and do the following:

根目录

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {
   @XmlElement(name="parent")
   List<Parent> allParents;
}

父母

@XmlAccessorType(XmlAccessType.FIELD)
public class Parent {
   @XmlElement(name="child")
   List<Child> allChildren;
}

<小时>

更新

是否可以避免父类?

有几种不同的方法可以实现这一点:

There are a couple of different ways to accomplish this:

选项 #1 - 使用 XmlAdapter 的任何 JAXB 实现

您可以使用 XmlAdapter 虚拟添加 Parent 类.

You could use an XmlAdapter to virtually add in the Parent class.

子适配器

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class ChildAdapter extends XmlAdapter<ChildAdapter.Parent, Child> {

    public static class Parent {
        public Child child;
    }

    @Override
    public Parent marshal(Child v) throws Exception {
        Parent parent = new Parent();
        parent.child = v;
        return parent;
    }

    @Override
    public Child unmarshal(Parent v) throws Exception {
        return v.child;
    }

}

根目录

@XmlJavaTypeAdapter注解用于引用XmlAdapter.

import java.util.List;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {

   @XmlElement(name="parent")
   @XmlJavaTypeAdapter(ChildAdapter.class)
   List<Child> allChildren;

}

儿童

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
public class Child {

    @XmlAttribute
    int id;

    @XmlAttribute
    String name;

}

选项 #2 - 使用 EclipseLink JAXB (MOXy)

如果您使用 EclipseLink JAXB (MOXy) 作为您的 JAXB (JSR-222) 实现然后您可以执行以下操作(注意:我MOXy 领导):

If you are using EclipseLink JAXB (MOXy) as your JAXB (JSR-222) implementation then you could do the following (Note: I'm the MOXy lead):

根目录

import java.util.List;
import javax.xml.bind.annotation.*;

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {

   @XmlElement(name="parent")
   List<Child> allChildren;

}

儿童

MOXy 的 @XmlPath 注释与您尝试在帖子中使用 @XmlElement 注释的方式非常相似.

MOXy's @XmlPath annotation works pretty much the way you are trying to use the @XmlElement annotation in your post.

import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;

@XmlAccessorType(XmlAccessType.FIELD)
public class Child {

    @XmlPath("child/@id")
    int id;

    @XmlPath("child/@name")
    String name;

}

了解更多信息

• http://blog.bdoughan.com/2010/07/xpath-based-mapping.html
• http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html

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