java - 没有注释的 JAXB Unmarshal

Question

我正在尝试解码一个没有注释的编码对象。

这是我的对象类。

class Student {
    private String name;
    private int age;

    public Student() {
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

这就是我用来编码对象的。

public String marshall(Student student){
        StringWriter writer = new StringWriter();
        JAXBContext context;
        try {
            context = JAXBContext.newInstance(Student.class);
            Marshaller m = context.createMarshaller();

            m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            JAXBElement<Student> rootElement = new JAXBElement<Student>(new QName("student"), Student.class, student);
            m.marshal(rootElement, writer);
            return writer.toString();
        } catch (JAXBException e) {
            e.printStackTrace();
            return null;
        }
    }

这就是我用来解码对象的方法。

public Student unMarshall(String input){
        JAXBContext context;
        try {
            context = JAXBContext.newInstance(Student.class);
            Unmarshaller m = context.createUnmarshaller();
            return (Student) m.unmarshal(new StringReader(input));
        } catch (JAXBException e) {
            e.printStackTrace();
            return null;
        }   
    }

当我尝试解码时，出现以下错误

javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"student"). Expected elements are (none)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:648)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:236)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:231)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:105)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1051)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:484)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:465)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:135)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:400)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:626)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3104)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:921)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:647)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:200)
    at com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:173)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:137)
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.unmarshal(AbstractUnmarshallerImpl.java:194)
    at noannotation.Main.unMarshel(Main.java:49)
    at noannotation.Main.main(Main.java:22)

我该如何解决这个错误？

Answer 1

您只需要使用带有Class 参数的unmarshal 方法之一。

public Student unMarshall(String input){
    JAXBContext context;
    try {
        context = JAXBContext.newInstance(Student.class);
        Unmarshaller m = context.createUnmarshaller();
        StreamSource source = new StreamSource(new StringReader(input))
        return m.unmarshal(source, Student.class).getValue();
    } catch (JAXBException e) {
        e.printStackTrace();
        return null;
    }   
}

了解更多信息

您可以在我的博客中找到有关此用例的更多信息:

• http://blog.bdoughan.com/2012/07/jaxb-no-annotations-required.html