java - JAXB XmlTransient 不起作用

Question

我正在尝试使用 JAXB 解码以下 XML:

<artist xmlns="http://www.spotify.com/ns/music/1">
   <name>Basement Jaxx</name>
   <albums>
      <album href="spotify:album:3xOulZzGRe4Ycwm59iCdKg">
         <name>Back 2 the Wild</name>
         <artist href="spotify:artist:4YrKBkKSVeqDamzBPWVnSJ">
            <name>Basement Jaxx</name>
         </artist>          
         <released>2013</released>
         <id type="upc">5055489272702</id>          
      <album>
   </albums>
</artist>

当我对专辑中的艺术家使用 @XmlTransient 以跳过它时，无论如何它都会被解析。

我该怎么做才能使 JAXB 正确处理标记为 @XmlTransient 的字段？

编辑 1 - 文件

测试 xml:

<artist>
     <name>Adema</name>
     <albums>
          <album href="spotify:album:07tjJowJIddz8c74x5WOvj">
               <name>Topple the Giants</name>
               <artist href="spotify:artist:3n4ersmDo55xV4fPSCKpXb">
                    <name>Adema</name>
               </artist>
               <released>2013</released>
               <id type="upc">886443922082</id>
               <availability>
                    <territories>AD AT AU BE CA CH DE DK EE ES FI FR GB HK IE IS IT LI LT LU LV MC MX MY NL NO NZ PL PT SE SG US</territories>
               </availability>
          </album>
          <album href="spotify:album:06QaJLqG068uXHQbAcPZKU">
               <name>Kill The Headlights</name>
               <artist href="spotify:artist:3n4ersmDo55xV4fPSCKpXb">
                    <name>Adema</name>
               </artist>
               <released>2007</released>
               <id type="upc">4030816195283</id>
               <availability>
                    <territories>AD AT BE CH DE DK EE ES FI FR GB IE IS IT LI LT LU LV MC NL NO PL PT SE</territories>
               </availability>
          </album>
    </albums>
</artist>

XTest.java:

package dao.spotify;

import dao.spotify.lookup.entities.LookupArtist;
import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.helpers.DefaultValidationEventHandler;

public class XTest {

    public XTest() {
        load();
    }

    public void load() {
        try { 
            File file = new File("c:/tmp/test5.xml");
            JAXBContext jc = JAXBContext.newInstance(LookupArtist.class);
            Unmarshaller um = jc.createUnmarshaller();
            um.setEventHandler(new DefaultValidationEventHandler());
            LookupArtist spotifyArtistWrapper = (LookupArtist) um.unmarshal(file);
            System.err.println("Done");
        } catch (JAXBException ex) {
            ex.printStackTrace();
        }
    }

    public static void main(String... args) {
        XTest test = new XTest();
    }
}

查找艺术家.java:

package dao.spotify.lookup.entities;

import java.util.ArrayList;
import java.util.List;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;

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

    @XmlElement
    private String name;
    @XmlElementWrapper(name = "albums")
    @XmlElement(name = "album")
    private List<LookupInnerAlbum> albums = new ArrayList();

}

LookupInnerAlbum.java:

package dao.spotify.lookup.entities;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;

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

    @XmlAttribute
    private String href;
    private String name;
    private int released;
    private String id;
    private LookupInnerAvailability availability;
    @XmlTransient
    private LookupInnerArtist artist;

}

LookupInnerAvailability.java:

package dao.spotify.lookup.entities;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

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

    @XmlElement
    private String territories;

}

LookupInnerArtist.java:

package dao.spotify.lookup.entities;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlType;

@XmlType(name = "artist")
@XmlAccessorType(XmlAccessType.FIELD)
public class LookupInnerArtist {

    @XmlElement
    private String name;
    @XmlAttribute
    private String href;
}

运行时我得到:

DefaultValidationEventHandler: [ERROR]: unexpected element (uri:"", local:"artist"). Expected elements are <{}id>,<{}released>,<{}name>,<{}availability> 
javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"artist"). Expected elements are <{}id>,<{}released>,<{}name>,<{}availability>
     Location: line 6 of file:/c:/tmp/test5.xml
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:662)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:258)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:253)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:120)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.childElement(Loader.java:105)
    at com.sun.xml.bind.v2.runtime.unmarshaller.StructureLoader.childElement(StructureLoader.java:262)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:498)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:480)
    at com.sun.xml.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:150)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:506)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:376)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2717)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:607)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:116)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:489)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:835)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:764)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:123)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1210)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:568)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:258)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:229)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:136)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:141)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:150)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:168)
    at dao.spotify.XTest.load(XTest.java:30)
    at dao.spotify.XTest.<init>(XTest.java:21)
    at dao.spotify.XTest.main(XTest.java:38)

Answer 1

当我运行您的示例时，我得到了同样的结果。报错信息正确unexpected element (uri:"", local:"artist")该元素存在于 XML 中，但您尚未映射到它。您映射到的预期元素是 <{}id>,<{}released>,<{}name>,<{}availability>元素 <{}artist>不会出现在那里，因为您已使用 @XmlTransient 排除了它.

DefaultValidationEventHandler: [ERROR]: unexpected element (uri:"", local:"artist"). Expected elements are <{}id>,<{}released>,<{}name>,<{}availability> 
     Location: line 6 of file:/Users/bdoughan/GIT/EclipseLink-Trunk3/Scratch/src/dao/spotify/test5.xml
javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"artist"). Expected elements are <{}id>,<{}released>,<{}name>,<{}availability>
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:642)

关于 DefaultValidationEventHandler 的注释.此类表示与 JAXB 2.0 不同的 JAXB 1.0 的默认验证事件规则。以下内容来自 Javadoc(参见:http://docs.oracle.com/javase/7/docs/api/javax/xml/bind/helpers/DefaultValidationEventHandler.html)

JAXB 1.0 only default validation event handler. This is the default handler for all objects created from a JAXBContext that is managing schema-derived code generated by a JAXB 1.0 binding compiler.

This handler causes the unmarshal and validate operations to fail on the first error or fatal error.

This handler is not the default handler for JAXB mapped classes following JAXB 2.0 or later versions. Default validation event handling has changed and is specified in Unmarshaller and Marshaller.

如果您没有将其指定为 ValidationEventHandler那么您的文档就会正确解码。

---

更新

I'm afraid I don't understand; I thought that I had mapped artist when specifying: private LookupInnerArtist artist;? When changing the DefaultValidationEventHandler to ValidationEventCollector (correct?) everything works fine, even if I have specified artist as @XmlTransient.

由于您指定了 @XmlAccessorType(XmlAccessType.FIELD)除了用 @XmlTransient 注释的字段之外的所有字段将被视为已映射。

I can still see artist when debugging, though it has a null value.

尽管artist注释为 @XmlTransient它仍然可以在您的类里面使用。因为它现在被认为是未映射的，所以它不会被解码操作填充。

了解更多信息

• http://blog.bdoughan.com/2012/04/jaxb-and-unmapped-properties.html