java - JAXB 从 Xml 模式生成的类不返回所有属性的 getter setter

Question

我正在使用 Jaxb 构建 Java 类以编码来自 upnp 的 xml 数据。 didlite 规范，所需的 xsd 文件可以在 https://gitlab.gnome.org/GNOME/gupnp-av/-/tree/master/data 找到

它可以工作，但不如我希望的那样好，有些元素不会为大多数属性甚至名称/值映射返回 getter 和 setter。相反，它们只是提供了所有 JAXBElement 的列表，我必须遍历这些 JAXBElement 才能找到我想要的属性，这是为什么呢？

/**
 * Gets the value of the allowedUnderItem property.
 * 
 * <p>
 * This accessor method returns a reference to the live list,
 * not a snapshot. Therefore any modification you make to the
 * returned list will be present inside the JAXB object.
 * This is why there is not a <CODE>set</CODE> method for the allowedUnderItem property.
 * 
 * <p>
 * For example, to add a new item, do as follows:
 * <pre>
 *    getAllowedUnderItem().add(newItem);
 * </pre>
 * 
 * 
 * <p>
 * Objects of the following type(s) are allowed in the list
 * {@link JAXBElement }{@code <}{@link ChannelGroupNameType }{@code >}
 * {@link JAXBElement }{@code <}{@link ChannelIDType }{@code >}
 * {@link JAXBElement }{@code <}{@link DayOfWeekEnLen3 }{@code >}
 * {@link JAXBElement }{@code <}{@link DescType }{@code >}
 * {@link JAXBElement }{@code <}{@link DeviceUDNType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ElementType }{@code >}
 * {@link JAXBElement }{@code <}{@link ForeignMetadataType }{@code >}
 * {@link JAXBElement }{@code <}{@link GenreType }{@code >}
 * {@link JAXBElement }{@code <}{@link InclusionType }{@code >}
 * {@link JAXBElement }{@code <}{@link ObjectLinkRefType }{@code >}
 * {@link JAXBElement }{@code <}{@link ObjectLinkType }{@code >}
 * {@link JAXBElement }{@code <}{@link OwnerType }{@code >}
 * {@link JAXBElement }{@code <}{@link PersonWithRoleType }{@code >}
 * {@link JAXBElement }{@code <}{@link PersonWithRoleType }{@code >}
 * {@link JAXBElement }{@code <}{@link PersonWithRoleType }{@code >}
 * {@link JAXBElement }{@code <}{@link PreservedTimeRangeType }{@code >}
 * {@link JAXBElement }{@code <}{@link PriceType }{@code >}
 * {@link JAXBElement }{@code <}{@link ProgramCodeType }{@code >}
 * {@link JAXBElement }{@code <}{@link ProgramIDType }{@code >}
 * {@link JAXBElement }{@code <}{@link ProgramIDType }{@code >}
 * {@link JAXBElement }{@code <}{@link ProgramListType }{@code >}
 * {@link JAXBElement }{@code <}{@link ProgramPreservedType }{@code >}
 * {@link JAXBElement }{@code <}{@link QualifiedDateTime }{@code >}
 * {@link JAXBElement }{@code <}{@link QualifiedDateTime }{@code >}
 * {@link JAXBElement }{@code <}{@link QualifiedDateTimeISO8601 }{@code >}
 * {@link JAXBElement }{@code <}{@link QualifiedDateTimeISO8601 }{@code >}
 * {@link JAXBElement }{@code <}{@link QualifiedDateTimeRange }{@code >}
 * {@link JAXBElement }{@code <}{@link RatingType }{@code >}
 * {@link JAXBElement }{@code <}{@link ResExtType }{@code >}
 * {@link JAXBElement }{@code <}{@link ResType }{@code >}
 * {@link JAXBElement }{@code <}{@link SearchClassType }{@code >}
 * {@link JAXBElement }{@code <}{@link SearchClassType }{@code >}
 * {@link JAXBElement }{@code <}{@link StateVariableCollectionType }{@code >}
 * {@link JAXBElement }{@code <}{@link StatusType }{@code >}
 * {@link JAXBElement }{@code <}{@link Boolean }{@code >}
 * {@link JAXBElement }{@code <}{@link Boolean }{@code >}
 * {@link JAXBElement }{@code <}{@link Boolean }{@code >}
 * {@link JAXBElement }{@code <}{@link Boolean }{@code >}
 * {@link JAXBElement }{@code <}{@link Integer }{@code >}
 * {@link JAXBElement }{@code <}{@link Integer }{@code >}
 * {@link JAXBElement }{@code <}{@link Integer }{@code >}
 * {@link JAXBElement }{@code <}{@link Integer }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link Long }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link String }{@code >}
 * {@link JAXBElement }{@code <}{@link List }{@code <}{@link String }{@code >}{@code >}
 * 
 * 
 */
public List<JAXBElement<?>> getAllowedUnderItem() {
    if (allowedUnderItem == null) {
        allowedUnderItem = new ArrayList<JAXBElement<?>>();
    }
    return this.allowedUnderItem;
}

意思是我必须写这样的代码

if(object instanceof ContainerType)
        {
            id = ((ContainerType)object).getId();
            title = ((ContainerType)object).getTitle().getValue();

            Iterator<JAXBElement<?>> i = ((ContainerType)object).getAllowedUnderContainer().iterator();
            while(i.hasNext())
            {
                JAXBElement next = i.next();
                if(next.getName().getLocalPart().equals("albumArtURI"))
                {
                    albumArtistUri = (String)next.getValue();
                }
            }
}   

我该如何改进？

Answer 1

虽然在这种情况下可能很困难，因为您正在使用的模式很复杂，但您可以尝试使用 JAXB XML bindings为此目的。

JAXB XML 绑定(bind)允许您以不同的方式自定义 JAXB Java 类生成过程。

在这些定制中，它允许您指示生成器使用您自己的类模型。

此信息应在绑定(bind) XML 文件中提供；在您的用例中，它可能与此类似:

<?xml version="1.0" encoding="UTF-8"?>
<jaxb:bindings 
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
    version="2.1">

    <jaxb:bindings schemaLocation="didl-lite-v2.xsd">
        <jaxb:bindings node="//xsd:complexType[@name='container.type']">
            <jaxb:class ref="didl.ContainerType"/>
        </jaxb:bindings>
        <jaxb:bindings node="//xsd:complexType[@name='item.type']">
            <jaxb:class ref="didl.ItemType"/>
        </jaxb:bindings>
    </jaxb:bindings>
</jaxb:bindings>

请注意自定义类 didl.ContainerType 和 didl.ItemType 的定义，以表示复杂类型 container.type 和 item.type，分别。

ContainerType 可能如下所示:

package didl;

import javax.xml.bind.annotation.XmlElement;

public class ContainerType {

  @XmlElement(
      name = "title", namespace = "http://purl.org/dc/elements/1.1/"
  )
  private String title;

  @XmlElement(
      name = "albumArtURI", namespace = "urn:schemas-upnp-org:metadata-1-0/upnp/"
  )
  private String albumArtURI;

  // Other fields

  public String getTitle() {
    return title;
  }

  public String getAlbumArtURI() {
    return albumArtURI;
  }
  
  // Other getters
}

我将在答案中使用 xjc 工具，但该解决方案应该可以轻松移植到 Maven，例如。

使用xjc，您需要像这样生成代码以考虑绑定(bind)文件和请求的类:

xjc -d output -b binding.xml didl-lite-v2.xsd -classpath /path/to/custom/classes

如您所见，我们提供了绑定(bind)文件 binding.xml 和生成器应在其中搜索自定义类的 classpath。

相同的方法，虽然用于更简单的用例，但已在 Stackoverflow 中的不同问题中举例说明，例如在这些问题中:

• JAXB xjc mapping to existing domain objects
• JAX-B - How to map a schema element to an existing Java class
• JAXB generates List<Jaxbelement> instead of fields

This Oracle article已经过时了，但它很好地解释了字段之间的实际对应关系是如何发生的。