JAXB unmarshaller.unmarshal何时返回JAXBElement 或MySchemaObject？

JAXB unmarshaller.unmarshal何时返回JAXBElement 或MySchemaObject？

如果根元素唯一地对应于Java类，则将返回该类的实例，否则将返回a

JAXBElement

。

如果要确保始终获取域对象的实例，则可以利用

JAXBInstrospector

。下面是一个例子。

演示版

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());    }}

输出量

class forum10243679.Rootclass forum10243679.Rootclass javax.xml.bind.JAXBElementclass forum10243679.Root