JAXB 用点定义 XML 元素答案

【问题标题】：JAXB Define XML elements with dotsJAXB 用点定义 XML 元素
【发布时间】：2021-04-23 17:45:15
【问题描述】：

我需要创建一个与此结构匹配的 XML：

<OfferPackage Name="aaa">
    <OfferPackage.Offers>
        <OfferCollection Capacity="1">
            <Offer Price="12.34"/>
            <Offer Price="12.34"/>
        </OfferCollection>
    </OfferPackage.Offers>
</OfferPackage>

我的问题是我不知道如何在这里实现：<OfferPackage.Offers>。我怎样才能只用注释来获得这个“点符号”？我得到的一切看起来像这样：

<OfferPackage Name="aaa">
  <OfferCollection Capacity="1">
    <Offer Price="12.34"/>
    <Offer Price="12.34"/>
  </OfferCollection>
</OfferPackage>

这是我当前的代码：

@XmlRootElement(name = "OfferPackage")
@XmlAccessorType(XmlAccessType.FIELD)
public class OfferPackage {
    
    @XmlAttribute(name = "Name")
    private String name = null;

    @XmlElement( name = "OfferCollection")
    private List<OfferCollection> offers = null;

    @SneakyThrows
    public String toString() {
        var sw = new StringWriter();
        var marshaller = JAXBContext
                .newInstance(OfferPackage.class)
                .createMarshaller();

        marshaller.setProperty(JAXB_FRAGMENT, true);
        marshaller.marshal(this, sw);

        return sw.toString();
    }
}

@XmlRootElement(name = "Offer")
@XmlAccessorType(XmlAccessType.FIELD)
public class OfferCollection {

    @XmlAttribute(name = "Capacity")
    private Integer capacity = null;

    @XmlElement(name = "Offer")
    private List<Offer> offer = null;
}

【问题讨论】：

标签： java xml annotations jaxb

【解决方案1】：

您可以使用@XmlElementWrapper annotation 实现所需的行为：

围绕 XML 表示生成一个包装器元素。这主要用于生成围绕集合的包装 XML 元素。

在您的情况下，它看起来类似于：

@XmlRootElement(name = "OfferPackage")
@XmlAccessorType(XmlAccessType.FIELD)
public class OfferPackage {
    
    @XmlAttribute(name = "Name")
    private String name = null;

    @XmlElementWrapper(name="OfferPackage.Offers")
    @XmlElement( name = "OfferCollection")
    private List<OfferCollection> offers = null;

    @SneakyThrows
    public String toString() {
        var sw = new StringWriter();
        var marshaller = JAXBContext
                .newInstance(OfferPackage.class)
                .createMarshaller();

        marshaller.setProperty(JAXB_FRAGMENT, true);
        marshaller.marshal(this, sw);

        return sw.toString();
    }
}

其他可能性是定义一个中间类 OfferPackageOffers 来包装 OfferCollection List::

@XmlRootElement(name = "OfferPackage.Offers")
@XmlAccessorType(XmlAccessType.FIELD)
public class OfferPackageOffers {

  @XmlElement( name = "OfferCollection")
  private List<OfferCollection> offers = null;

  //...
}

并使用OfferPackage 中的新类而不是提到的OfferCollection List：

@XmlRootElement(name = "OfferPackage")
@XmlAccessorType(XmlAccessType.FIELD)
public class OfferPackage {

  @XmlAttribute(name = "Name")
  private String name = null;

  @XmlElement( name = "OfferPackage.Offers")
  private OfferPackageOffers offers = null;

  //...

}

【讨论】：