[英]I get the error as “missing an @XmlRootElement annotation” while trying to marshall an object into xml file using JAXB
I am someone who has just started to use JAXB,All I need it for is write an object into xml and read it back into java at some point 我是刚开始使用JAXB的人,我需要做的就是将对象写入xml并在某个时候将其读回Java
Here is my class: 这是我的课:
public class VSM implements java.io.Externalizable
{
ArrayList<String> termList; //Term Dictionary
ArrayList<String> queryTermList; //Query list
ArrayList<ArrayList<Doc>> docLists;
ArrayList<ArrayList<Doc>> queryDocLists;
double[] docLength; //Denominator for doc linearization
double queryLength; //Denominator for query lineriazation
HashMap<String, Double> queryDocLenght; //Vector for holding noramiliase queries
HashMap<String, Double> queryDoc;
String Docs[]; //List of file names
Double scoreCap=0.04; //Score cap to reduce the effect of stop words
public static String fileName = "indexedFiles.txt";
private static final long serialVersionUID = 7863262235394607247L;
public VSM()
{
//Some constructor code
}
}
Here is the method I use to construct the XML file 这是我用来构造XML文件的方法
public void writeXML(VSM vsm)
{
try {
File file = new File("IndexXmlfile.xml");
//JAXBElement<VSM> jaxbWrappedHeader = objectFactory.createHeader(obj);
JAXBContext jaxbContext = JAXBContext.newInstance(VSM.class);
Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
// output pretty printed
jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
jaxbMarshaller.marshal(new JAXBElement<VSM>(new QName("uri","local"), VSM.class, vsm), System.out);
jaxbMarshaller.marshal(vsm, file);
jaxbMarshaller.marshal(vsm, System.out);
} catch (JAXBException e) {
e.printStackTrace();
}
}
Altough WHen I try to run the code I get the error as : 当我尝试运行代码时,出现以下错误:
javax.xml.bind.MarshalException
- with linked exception:
[com.sun.istack.SAXException2: unable to marshal type "KPT.VSM" as an element because it is missing an @XmlRootElement annotation]
at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:326)
at com.sun.xml.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:251)
at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(Unknown Source)
at KPT.VSM.writeXML(VSM.java:477)
at KPT.VSM.main(VSM.java:511)
Caused by: com.sun.istack.SAXException2: unable to marshal type "KPT.VSM" as an element because it is missing an @XmlRootElement annotation
at com.sun.xml.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:249)
at com.sun.xml.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:339)
at com.sun.xml.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:494)
at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:323)
... 4 more
I dont understand JABX and all it methods fully yet ,so its kind of difficult for me understand this error,I tried googling a little and found a lot of people get this error, but still find it difficult to understand the problem the solution here.. 我还不完全了解JABX及其所有方法,因此它对我来说很难理解此错误,我尝试了一下Google搜寻,发现很多人都遇到了这个错误,但是仍然很难在这里理解问题的解决方案。 。
When your class is not annotated with @XmlRootElement
then you need to wrap it in an instance of JAXBElement
as you have done for one of your marshal
operations: 当你的类不带注释
@XmlRootElement
那么你需要用它的一个实例JAXBElement
为你做你的一个marshal
操作:
jaxbMarshaller.marshal(new JAXBElement<VSM>(new QName("uri","local"), VSM.class, vsm), System.out);
The exception is coming from the time you try to marshal the instance of VSM
wihtout doing that: 例外是您尝试封送
VSM
实例的时间而来的:
jaxbMarshaller.marshal(vsm, System.out);
Thanks for ur answer,doing that only let me create empty xml file, but now I know what I was doing wrong, it was stupid of me trying to write an xml without specifying the annoations
谢谢你的回答,这样做只会让我创建一个空的xml文件,但是现在我知道自己做错了,这很愚蠢,因为我试图在不指定注释的情况下编写xml
JAXB (JSR-222) implementations don't require any annotations (see: http://blog.bdoughan.com/2012/07/jaxb-no-annotations-required.html ). JAXB(JSR-222)实现不需要任何注释(请参阅: http : //blog.bdoughan.com/2012/07/jaxb-no-annotations-required.html )。 The most common annotation added is
@XmlRootElement
, but without it you can use JAXBElement
(see: http://blog.bdoughan.com/2012/07/jaxb-and-root-elements.html ). 添加的最常见的注释是
@XmlRootElement
,但是如果没有它,则可以使用JAXBElement
(请参阅: http : @XmlRootElement
)。 If your class does not have public accessor methods then you may also be interested in the @XmlAccessorType(XmlAccessType.FIELD)
annotation (see: http://blog.bdoughan.com/2011/06/using-jaxbs-xmlaccessortype-to.html ). 如果您的类没有公共访问器方法,那么您可能也对
@XmlAccessorType(XmlAccessType.FIELD)
注释感兴趣(请参阅: http : @XmlAccessorType(XmlAccessType.FIELD)
。 html )。
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