java - 困难的 JAXB 映射

Question

我正在尝试在更大的文档中映射以下 XML 结构，显然这不是 XML 的最大用途，但这是我必须处理的。

为清楚起见简化的示例:

  <details>
    <pictures>
      <picture1>
        http://domain.com/path/picture1.jpg
      </picture1>
      <picture2>
        http://domain.com/path/picture2.jpg
      </picture2>
      <picture3>
        http://domain.com/path/picture3.jpg
      </picture3>
      <picture4>
        http://domain.com/path/picture4.jpg
      </picture4>
      <picture5>
        http://domain.com/path/picture5.jpg
      </picture5>
      <picture6>
        http://domain.com/path/picture6.jpg
      </picture6>
      <picture7>
        http://domain.com/path/picture7.jpg
      </picture7>
    </pictures>
  </details>

此文档有一个 DTD，它声明将有多达 30 个不同的图片元素，编号为 1-30，名称为 <picutre[n]/>。

我想做的是，而不是为这些称为 Picture1、Picture2、Picture3 等的每个元素创建 30 个不同的类。我只想使用一个图片类并将其用于所有 30 个唯一元素名称。

以下是我到目前为止尝试过的方法。

@XmlRootElement
public class Details {

   ...

   @XmlElementWrapper
   @XmlElementRefs({
        @XmlElementRef( name="picture1", type=Picture.class ),
        @XmlElementRef( name="picture2", type=Picture.class ),
        @XmlElementRef( name="picture3", type=Picture.class ),
        @XmlElementRef( name="picture4", type=Picture.class ),
        @XmlElementRef( name="picture5", type=Picture.class ),
        @XmlElementRef( name="picture6", type=Picture.class ),
        @XmlElementRef( name="picture7", type=Picture.class ),
        @XmlElementRef( name="picture8", type=Picture.class ),
        @XmlElementRef( name="picture9", type=Picture.class ),
        @XmlElementRef( name="picture10", type=Picture.class ),
        @XmlElementRef( name="picture11", type=Picture.class ),
        @XmlElementRef( name="picture12", type=Picture.class ),
        @XmlElementRef( name="picture13", type=Picture.class ),
        @XmlElementRef( name="picture14", type=Picture.class ),
        @XmlElementRef( name="picture15", type=Picture.class ),
        @XmlElementRef( name="picture16", type=Picture.class ),
        @XmlElementRef( name="picture17", type=Picture.class ),
        @XmlElementRef( name="picture18", type=Picture.class ),
        @XmlElementRef( name="picture19", type=Picture.class ),
        @XmlElementRef( name="picture20", type=Picture.class ),
        @XmlElementRef( name="picture21", type=Picture.class ),
        @XmlElementRef( name="picture22", type=Picture.class ),
        @XmlElementRef( name="picture23", type=Picture.class ),
        @XmlElementRef( name="picture24", type=Picture.class ),
        @XmlElementRef( name="picture25", type=Picture.class ),
        @XmlElementRef( name="picture26", type=Picture.class ),
        @XmlElementRef( name="picture27", type=Picture.class ),
        @XmlElementRef( name="picture28", type=Picture.class ),
        @XmlElementRef( name="picture29", type=Picture.class ),
        @XmlElementRef( name="picture30", type=Picture.class )
    })
   public List<Picture> getPictures() {
      return this.pictures;
   }

   public void setPictures( List<Pictures> pictures ) {
      this.pictures = pictures;
   }

   ...

}

@XmlElementWrapper
public class Picture {
 ...
}

这会导致 getPictures 始终返回 null。

此外，我尝试将 Picture 类上的注释更改为 @XmlElementWrapper( name="picture1" )这导致我得到一个从 getPictures() 返回的列表，但只包含 <picture1/>元素，而不是其余部分。

我知道我可以求助于获取 JAXBElement 对象的列表，但如果可以避免，我宁愿不这样做。有什么想法可以映射吗？

Answer 1

有几种方法可以处理这个用例:

选项#1

您可以利用 @XmlElements 执行以下操作:

package forum10109418;

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

@XmlRootElement
public class Details {

   private List<Picture> pictures;

   @XmlElementWrapper
   @XmlElements({
       @XmlElement( name="picture1", type=Picture.class ),
       @XmlElement( name="picture2", type=Picture.class ),
       @XmlElement( name="picture3", type=Picture.class ),
       @XmlElement( name="picture4", type=Picture.class ),
       @XmlElement( name="picture5", type=Picture.class ),
       @XmlElement( name="picture6", type=Picture.class ),
       @XmlElement( name="picture7", type=Picture.class ),
       @XmlElement( name="picture8", type=Picture.class ),
       @XmlElement( name="picture9", type=Picture.class ),
       @XmlElement( name="picture10", type=Picture.class ),
       @XmlElement( name="picture11", type=Picture.class ),
       @XmlElement( name="picture12", type=Picture.class ),
       @XmlElement( name="picture13", type=Picture.class ),
       @XmlElement( name="picture14", type=Picture.class ),
       @XmlElement( name="picture15", type=Picture.class ),
       @XmlElement( name="picture16", type=Picture.class ),
       @XmlElement( name="picture17", type=Picture.class ),
       @XmlElement( name="picture18", type=Picture.class ),
       @XmlElement( name="picture19", type=Picture.class ),
       @XmlElement( name="picture20", type=Picture.class ),
       @XmlElement( name="picture21", type=Picture.class ),
       @XmlElement( name="picture22", type=Picture.class ),
       @XmlElement( name="picture23", type=Picture.class ),
       @XmlElement( name="picture24", type=Picture.class ),
       @XmlElement( name="picture25", type=Picture.class ),
       @XmlElement( name="picture26", type=Picture.class ),
       @XmlElement( name="picture27", type=Picture.class ),
       @XmlElement( name="picture28", type=Picture.class ),
       @XmlElement( name="picture29", type=Picture.class ),
       @XmlElement( name="picture30", type=Picture.class )
   })

   public List<Picture> getPictures() {
      return this.pictures;
   }

   public void setPictures( List<Picture> pictures ) {
      this.pictures = pictures;
   }

}

选项#2

您可以按如下方式映射您的Details 类:

package forum10109418;

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

@XmlRootElement
public class Details {

   private List<Picture> pictures;

   @XmlElementWrapper
   @XmlElement(name="picture")
   public List<Picture> getPictures() {
      return this.pictures;
   }

   public void setPictures( List<Picture> pictures ) {
      this.pictures = pictures;
   }

}

然后使用 StreamReaderDelegate 来切断数字后缀:

package forum10109418;

import java.io.FileInputStream;
import javax.xml.bind.*;
import javax.xml.stream.*;
import javax.xml.stream.util.StreamReaderDelegate;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Details.class);

        XMLInputFactory xif = XMLInputFactory.newFactory();
        XMLStreamReader xsr = xif.createXMLStreamReader(new FileInputStream("src/forum10109418/input.xml"));
        xsr = new StreamReaderDelegate(xsr) {
            @Override
            public String getLocalName() {
                String localName = super.getLocalName();
                if(localName.startsWith("picture") && !localName.equals("pictures")) {
                    return "picture";
                }
                return localName;
            }

        };
        Unmarshaller unmarshaller = jc.createUnmarshaller();
        Details details = (Details) unmarshaller.unmarshal(xsr);
        System.out.println(details.getPictures().size());
    }

}

选项 #3

如果您使用 EclipseLink MOXy作为你的JAXB (JSR-222)提供程序，那么您可以使用我们添加的 @XmlVariableNode 扩展:

• http://blog.bdoughan.com/2013/06/mapping-bad-xml-enumerated-collection.html