Java JAXB unmarshaller.unmarshal何时返回JAXBElement<;MySchemaObject>;还是一个神秘的对象?
我有两个代码,在两个不同的java项目中,执行几乎相同的操作(根据xsd文件解组Web服务的输入) 但在一个例子中,我应该这样写:(Input是一个占位符名称)(element是OMElement Input) 在另一个库中,我必须使用JAXBElement.getValue(),因为它是一个返回的JAXBElement,而简单(输入)转换只是崩溃:Java JAXB unmarshaller.unmarshal何时返回JAXBElement<;MySchemaObject>;还是一个神秘的对象?,java,jaxb,unmarshalling,Java,Jaxb,Unmarshalling,我有两个代码,在两个不同的java项目中,执行几乎相同的操作(根据xsd文件解组Web服务的输入) 但在一个例子中,我应该这样写:(Input是一个占位符名称)(element是OMElement Input) 在另一个库中,我必须使用JAXBElement.getValue(),因为它是一个返回的JAXBElement,而简单(输入)转换只是崩溃: Input input = (Input)unmarshaller.unmarshal( element.getXMLStreamReader()
Input input = (Input)unmarshaller.unmarshal( element.getXMLStreamReader() ).getValue();
您知道是什么导致了这样的差异吗?您需要将正确的
@XMLRootElement
添加到JAXB生成的类中-它应该具有名称空间:
@XmlRootElement(namespace="http://your.namespace.com/", name="yourRootElement")
看看相关的问题(有很多好的提示):这取决于根元素的类上是否存在 如果从XSD生成JAXB类,将应用以下规则:
- 如果根元素的类型是匿名类型->XmlRootElement注释将添加到生成的类中
- 如果根元素的类型是顶级类型,则生成的类中将忽略XmlRootElement注释
<jxb:bindings version="1.0"
xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<jxb:bindings schemaLocation="yourXsd.xsd" node="/xs:schema">
<jxb:bindings node="//xs:element[@name='yourRootElement']">
<jxb:class name="YourRootElementType"/>
</jxb:bindings>
</jxb:bindings>
</jxb:bindings>
多亏了您的解释和链接,我写这篇文章是为了通过注释内省来处理这两种情况 这具有以下优点:
- 不修改生成的java类
- 允许所有可能的xsd格式
public class JaxbWrapper {
private static boolean isXmlRootElement(Class classT){
Annotation[] annotations = classT.getAnnotations();
for(Annotation annotation : annotations){
if(annotation instanceof XmlRootElement){
return true;
}
}
return false;
}
public static Object unmarshall(Class classObjectFactory, Class classObject, XMLStreamReader xmlStreamReader){
Package pack = classObjectFactory.getPackage();
String strPackageName = pack.getName();
Object returnObject = null;
try {
JAXBContext jc = JAXBContext.newInstance(strPackageName, classObjectFactory.getClassLoader());
Unmarshaller unmarshaller = jc.createUnmarshaller();
returnObject = unmarshaller.unmarshal( xmlStreamReader );
boolean bIsRootedElement = isXmlRootElement(classObject);
if(!bIsRootedElement)
{
JAXBElement jaxbElement = (JAXBElement) returnObject;
returnObject = jaxbElement.getValue();
}
}
catch (JAXBException e) {
/*...*/
}
return returnObject;
}
private static void writeToXml(Class classObjectFactory, Object obj, XMLStreamWriter xmlStreamWriter){
Package pack = classObjectFactory.getPackage();
String strPackageName = pack.getName();
try {
JAXBContext jc = JAXBContext.newInstance(strPackageName, classObjectFactory.getClassLoader());
Marshaller marshaller = jc.createMarshaller();
marshaller.marshal(obj, xmlStreamWriter);
}
catch(JAXBException e) {
/*...*/
}
}
public static String marshall(Class classObjectFactory, Class classObject, Object obj){
Object objectToMarshall = obj;
boolean bIsRootedElement = isXmlRootElement(classObject);
if(!bIsRootedElement)
{
Package pack = classObjectFactory.getPackage();
String strPackageName = pack.getName();
String strClassName = classObject.getName();
QName qName = new QName(strPackageName, strClassName);
JAXBElement jaxbElement = new JAXBElement(qName, classObject, null, obj);
objectToMarshall = jaxbElement;
}
StringWriter sw = new StringWriter();
XMLOutputFactory xmlOutputFactory = XMLOutputFactory.newInstance();
XMLStreamWriter xmlStreamWriter = null;
try {
xmlStreamWriter = xmlOutputFactory.createXMLStreamWriter(sw);
writeToXml(classObjectFactory, objectToMarshall, xmlStreamWriter);
xmlStreamWriter.flush();
xmlStreamWriter.close();
}
catch (XMLStreamException e) {
/*...*/
}
return sw.toString();
}
}
如果根元素唯一地对应于一个Java类,那么将返回该类的实例,如果不是,则返回
JAXBElement
如果要确保始终获得域对象的实例,可以利用JAXBInstrospector
。下面是一个例子
演示
package forum10243679;
import java.io.StringReader;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;
public class Demo {
private static final String XML = "<root/>";
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Root.class);
Unmarshaller unmarshaller = jc.createUnmarshaller();
JAXBIntrospector jaxbIntrospector = jc.createJAXBIntrospector();
Object object = unmarshaller.unmarshal(new StringReader(XML));
System.out.println(object.getClass());
System.out.println(jaxbIntrospector.getValue(object).getClass());
Object jaxbElement = unmarshaller.unmarshal(new StreamSource(new StringReader(XML)), Root.class);
System.out.println(jaxbElement.getClass());
System.out.println(jaxbIntrospector.getValue(jaxbElement).getClass());
}
}
我也有同样的问题。JAXB unmarshaller.unmarshal返回一个
JAXBElement
,而不是所需的MyObject
我找到并删除了
@xmlementdecl
。问题已经解决。我认为查看XSD是有意义的,因为这取决于您是将其解组为SimpleType还是ComplexType。注意:名称空间也可以使用@javax.xml.bind.annotation.XmlSchema包注释指定(通常在package info.java中)您应该能够利用JAXBIntrospector
类来简化代码。我添加了一个答案:出于好奇,为什么您要将您的包命名为forum10243679
?@Saintali-我尝试为我的每个答案提供一个工作代码示例。如果需要重新访问,包名可以帮助我找到代码示例。我将前缀forum
用于对应于公共论坛(如Stack Overflow)的代码示例(我使用bug前缀来重新创建bug),数字对应于URL中可以找到的问题ID。
package forum10243679;
import java.io.StringReader;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;
public class Demo {
private static final String XML = "<root/>";
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Root.class);
Unmarshaller unmarshaller = jc.createUnmarshaller();
JAXBIntrospector jaxbIntrospector = jc.createJAXBIntrospector();
Object object = unmarshaller.unmarshal(new StringReader(XML));
System.out.println(object.getClass());
System.out.println(jaxbIntrospector.getValue(object).getClass());
Object jaxbElement = unmarshaller.unmarshal(new StreamSource(new StringReader(XML)), Root.class);
System.out.println(jaxbElement.getClass());
System.out.println(jaxbIntrospector.getValue(jaxbElement).getClass());
}
}
class forum10243679.Root
class forum10243679.Root
class javax.xml.bind.JAXBElement
class forum10243679.Root