JAXB如何解编组命名空间？

Question

<A xmlns="something">
   <B>4</B>
</A>

我的代码如下：

@XmlRootElement(name = "A")
@XmlAccessorType (XmlAccessType.FIELD)
@Getter //from lombok
public class Data{

@XmlElement(name = "B")
private String b;

public Data(String b) {
    this.b = b;
}

public Data() {
}
// Getter/setter generated by lombok.
}

我怎样才能让它工作？如果我的xml标记有一些相关元素，如上面的“xmlns”，则JAXB解组器会抛出异常。

这是我第一次这么做，所以我对JAXB、解编等都一无所知。我在苦苦挣扎任何帮助都是好的。

编辑StackTrace：

javax.xml.bind.UnmarshalException: unexpected element (uri:"something", local:"A"). Expected elements are <{}B>,<{}A>
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:726)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:247)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:242)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:109)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1131)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:556)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:538)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:153)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:509)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:374)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:613)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3132)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:852)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:112)
at   com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
at ...

Answer 1

所有您需要的是添加一个@XmlAt0016到A（alogn与相应的getter/setter）

@XmlRootElement(name = "A")
@XmlAccessorType (XmlAccessType.FIELD)
@Getter //from lombok
public class Data{

@XmlAttribute(name="xmln")
String attr;
@XmlElement(name = "B")
private String b;

public Data(String b) {
    this.b = b;
}

   public Data() {
 }
// Getter/setter generated by lombok.
    public String getAttr(){
    return attr;
    }
    public void setAttr(String attr){
    this.attr = attr;
  }
  }

编辑：这并不能回答问题，因为问题是关于xml名称空间而不是属性的。

Answer 2

如果xml文档中有名称空间，那么jaxb注释中也需要有名称空间。

例如像这样：

@XmlRootElement(name = "A", namespace="something")
@XmlAccessorType (XmlAccessType.FIELD)
public class Data{

Answer 3

从XmlRootElement的来源：

public @interface XmlRootElement {
    /**
     * namespace name of the XML element.
     * <p>
     * If the value is "##default", then the XML namespace name is derived
     * from the package of the class ( {@link XmlSchema} ). If the
     * package is unnamed, then the XML namespace is the default empty
     * namespace.
     */
    String namespace() default "##default";
     // else of file

您还应该记住，这条规则也适用于大多数JAXB注释，所以您需要指定根元素和其他明确给出命名空间的元素，比如：

@XmlRootElement(namespace="something", name = "A")
@XmlAccessorType (XmlAccessType.FIELD)
@Getter //from lombok
public class Data{
    @XmlElement(namespace="something", name = "B") // <-- mind this
    private String b;

    public Data(String b) {
        this.b = b;
    }

    public Data() {
    }
    // Getter/setter generated by lombok.
}

如果你不这样做，它会期望，假设你的Data在org.example包中，命名空间org.example中的一些元素，只要你有@XmlSchema（elementFormDefault=QUALIFIED），否则它将期望默认命名空间中的元素。