JAXB 解组：ElementNSImpl 从何而来？
JAXB unmarshall: where does ElementNSImpl come from?
当我解组某个对象时，我没有返回对象的类型，而是类型 ElementNSImpl 似乎有我的数据，但为什么 JAXB 不将它解组到我的 JAXB classes?
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "Asset", propOrder = {
"platformContentOrFeatureContentOrAirspace",
...
})
@XmlSeeAlso({
...
})
public abstract class Asset {
@XmlElements({
@XmlElement(name = "PlatformContent", type = AnyPlatform.class),
@XmlElement(name = "FeatureContent", type = AnyFeature.class),
@XmlElement(name = "Airspace", type = Airspace.class)
})
protected Object platformContentOrFeatureContentOrAirspace;
...
public Object getPlatformContentorFeatureContentorAirspace(){
return platformContentOrFeatureContentOrAirspace;
}
...
}
这是一个架构片段：
<complexType name="Asset">
<complexContent>
<restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
<sequence>
<choice minOccurs="0">
<element name="PlatformContent" type="temp:TargetNamespaceURI}AnyPlatform"/>
<element name="FeatureContent" type="{temp:TargetNamespaceURI}AnyFeature"/>
<element ref="{temp:TargetNamespaceURI}Airspace"/>
</choice>
</sequence>
</restriction>
</complexContent>
</complexType>
更新：
在这种情况下，我试图解组包含 PlatformContent 标记的 XML。如果我取出 @XmlTransient 注释，我会得到一个异常，说明它无法实例化 AnyPlatform。我是 JAXB 的新手，但我意识到这可能是一个错误的步骤，并且绕过了我的问题，将 @XmlTransient 留在了
中
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "AnyPlatform", propOrder = {
"fooOrBarOrBaz"
})
@XmlTransient //This may be needed to parse correctly.
@XmlSeeAlso({
AnyPlatformDerivedType1.class,
AnyPlatformDerivedType2.class
})
public abstract class AnyPlatform {
@XmlElements({
@XmlElement(name = "Foo", type = Foo.class),
@XmlElement(name = "Bar", type = Bar.class),
@XmlElement(name = "Baz", type = Baz.class),
})
protected PlatformType fooOrBarOrBaz;
public PlatformType getFooOrBarOrBaz() {
return fooOrBarOrBaz;
}
}
这是架构片段
<xs:complexType name="AnyPlatform" abstract="true">
<xs:choice>
<xs:element ref="Foo"/>
<xs:element ref="Bar"/>
<xs:element ref="Baz"/>
</xs:choice>
</xs:complexType>
当 @XmlTransient 被删除时，我得到这个异常：
javax.xml.bind.UnmarshalException: Unable to create an instance of AnyPlatform
- with linked exception:
[java.lang.InstantiationException]
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.UnmarshallingContext.createInstance(UnmarshallingContext.java:690)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.StructureLoader.startElement(StructureLoader.java:171)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.XsiTypeLoader.startElement(XsiTypeLoader.java:65)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:559)
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:380)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2787)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:118)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:243)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:214)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:125)
at App.parse(App.java:66)
at MainWindow.actionPerformed(MainWindow.java:57)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access0(EventQueue.java:97)
at java.awt.EventQueue.run(EventQueue.java:709)
at java.awt.EventQueue.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue.run(EventQueue.java:731)
at java.awt.EventQueue.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.lang.InstantiationException
at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.sun.xml.internal.bind.v2.ClassFactory.create0(ClassFactory.java:118)
at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.createInstance(ClassBeanInfoImpl.java:270)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.createInstance(UnmarshallingContext.java:684)
... 60 more
更新 2
这是有问题的 XML：
<p:AssetList>
<p:Asset>
<p:PlatformContent>
<p:Foo>
<!-- Foo's Data -->
</p:Foo>
</p:PlatformContent>
</p:Asset>
</p:AssetList>
更新3
为了更加清晰，AnyPlatform 是两个派生的 classes 的基础 class。我们将它们称为 AnyPlatformDerivedClass1 和 AnyPlatformDerivedClass2。这是它们的样子：
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "AnyPlatformDerivedType1")
public class AnyPlatformDerivedType1
extends AnyPlatform
{
// Yes. These really are empty according to the schema.
}
根据架构，它们是故意留空的。所以这基本上只是具有不同 XML 标签名称的相同内容。
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "AnyPlatformDerivedType2")
public class AnyPlatformDerivedType2
extends AnyPlatform
{
// Yes. These really are empty according to the schema.
}
只要您使用 xsi:type 作为鉴别器并且具体实现在 JAXBContext 中（直接添加或通过 XmlSeeAlso 引用），它就可以充分发挥作用。这是一个例子：
class QuickTest {
@XmlRootElement
public static class Container {
@XmlElement
public Base base;
}
public static abstract class Base {
}
@XmlType(name="one")
public static class ChildOne extends Base {
}
@XmlType(name="two")
public static class ChildTwo extends Base {
}
private static final String MESSAGE = "<container xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"><base xsi:type=\"one\"/></container>";
public static void main(String [] args) throws Exception {
JAXBContext context = JAXBContext.newInstance(Container.class, Base.class, ChildOne.class, ChildTwo.class);
Container con = (Container) context.createUnmarshaller().unmarshal(new StringReader(MESSAGE));
System.out.println(con.base.getClass());
//Prints QuickTest$ChildOne
}
}
我最终从 AnyPlatform 中删除了抽象关键字。一切都按预期工作，现在对我来说不太可能在未来需要它。
当我解组某个对象时，我没有返回对象的类型，而是类型 ElementNSImpl 似乎有我的数据，但为什么 JAXB 不将它解组到我的 JAXB classes?
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "Asset", propOrder = {
"platformContentOrFeatureContentOrAirspace",
...
})
@XmlSeeAlso({
...
})
public abstract class Asset {
@XmlElements({
@XmlElement(name = "PlatformContent", type = AnyPlatform.class),
@XmlElement(name = "FeatureContent", type = AnyFeature.class),
@XmlElement(name = "Airspace", type = Airspace.class)
})
protected Object platformContentOrFeatureContentOrAirspace;
...
public Object getPlatformContentorFeatureContentorAirspace(){
return platformContentOrFeatureContentOrAirspace;
}
...
}
这是一个架构片段：
<complexType name="Asset">
<complexContent>
<restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
<sequence>
<choice minOccurs="0">
<element name="PlatformContent" type="temp:TargetNamespaceURI}AnyPlatform"/>
<element name="FeatureContent" type="{temp:TargetNamespaceURI}AnyFeature"/>
<element ref="{temp:TargetNamespaceURI}Airspace"/>
</choice>
</sequence>
</restriction>
</complexContent>
</complexType>
更新：
在这种情况下，我试图解组包含 PlatformContent 标记的 XML。如果我取出 @XmlTransient 注释，我会得到一个异常，说明它无法实例化 AnyPlatform。我是 JAXB 的新手，但我意识到这可能是一个错误的步骤，并且绕过了我的问题，将 @XmlTransient 留在了
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "AnyPlatform", propOrder = {
"fooOrBarOrBaz"
})
@XmlTransient //This may be needed to parse correctly.
@XmlSeeAlso({
AnyPlatformDerivedType1.class,
AnyPlatformDerivedType2.class
})
public abstract class AnyPlatform {
@XmlElements({
@XmlElement(name = "Foo", type = Foo.class),
@XmlElement(name = "Bar", type = Bar.class),
@XmlElement(name = "Baz", type = Baz.class),
})
protected PlatformType fooOrBarOrBaz;
public PlatformType getFooOrBarOrBaz() {
return fooOrBarOrBaz;
}
}
这是架构片段
<xs:complexType name="AnyPlatform" abstract="true">
<xs:choice>
<xs:element ref="Foo"/>
<xs:element ref="Bar"/>
<xs:element ref="Baz"/>
</xs:choice>
</xs:complexType>
当 @XmlTransient 被删除时，我得到这个异常：
javax.xml.bind.UnmarshalException: Unable to create an instance of AnyPlatform
- with linked exception:
[java.lang.InstantiationException]
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.UnmarshallingContext.createInstance(UnmarshallingContext.java:690)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.StructureLoader.startElement(StructureLoader.java:171)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.XsiTypeLoader.startElement(XsiTypeLoader.java:65)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:559)
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:380)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2787)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:118)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:243)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:214)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:157)
at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:125)
at App.parse(App.java:66)
at MainWindow.actionPerformed(MainWindow.java:57)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access0(EventQueue.java:97)
at java.awt.EventQueue.run(EventQueue.java:709)
at java.awt.EventQueue.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue.run(EventQueue.java:731)
at java.awt.EventQueue.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.lang.InstantiationException
at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.sun.xml.internal.bind.v2.ClassFactory.create0(ClassFactory.java:118)
at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.createInstance(ClassBeanInfoImpl.java:270)
at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.createInstance(UnmarshallingContext.java:684)
... 60 more
更新 2 这是有问题的 XML：
<p:AssetList>
<p:Asset>
<p:PlatformContent>
<p:Foo>
<!-- Foo's Data -->
</p:Foo>
</p:PlatformContent>
</p:Asset>
</p:AssetList>
更新3 为了更加清晰，AnyPlatform 是两个派生的 classes 的基础 class。我们将它们称为 AnyPlatformDerivedClass1 和 AnyPlatformDerivedClass2。这是它们的样子：
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "AnyPlatformDerivedType1")
public class AnyPlatformDerivedType1
extends AnyPlatform
{
// Yes. These really are empty according to the schema.
}
根据架构，它们是故意留空的。所以这基本上只是具有不同 XML 标签名称的相同内容。
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "AnyPlatformDerivedType2")
public class AnyPlatformDerivedType2
extends AnyPlatform
{
// Yes. These really are empty according to the schema.
}
只要您使用 xsi:type 作为鉴别器并且具体实现在 JAXBContext 中（直接添加或通过 XmlSeeAlso 引用），它就可以充分发挥作用。这是一个例子：
class QuickTest {
@XmlRootElement
public static class Container {
@XmlElement
public Base base;
}
public static abstract class Base {
}
@XmlType(name="one")
public static class ChildOne extends Base {
}
@XmlType(name="two")
public static class ChildTwo extends Base {
}
private static final String MESSAGE = "<container xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"><base xsi:type=\"one\"/></container>";
public static void main(String [] args) throws Exception {
JAXBContext context = JAXBContext.newInstance(Container.class, Base.class, ChildOne.class, ChildTwo.class);
Container con = (Container) context.createUnmarshaller().unmarshal(new StringReader(MESSAGE));
System.out.println(con.base.getClass());
//Prints QuickTest$ChildOne
}
}
我最终从 AnyPlatform 中删除了抽象关键字。一切都按预期工作，现在对我来说不太可能在未来需要它。