解组错误Jaxb-“类没有默认的无参数构造函数”，而有默认的无参数构造函数

Question

I'm trying to unmarshal the following XML but getting an exception: "1 counts of IllegalAnnotationExceptions EntityVersionInfo does not have a no-arg default constructor." despite actually having a no args constructor. What am I missing?

XML:

<topLevelObject>
  <entityVersionInfo>
        <id>111111</id>
        <version>1</version>
  </entityVersionInfo>
</topLevelObject>

Entities in Java with Annotations:

TopLevelObject:

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "topLevelObject")

public class TopLevelObject {

    @XmlElement(name = "entityVersionInfo")
    private EntityVersionInfo versionInfo;

    public TopLevelObject() {
        //no args constructor
    }

    //GETTERS AND SETTERS HERE...
}

EntityVersionInfo:

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "entityVersionInfo")

public class EntityVersionInfo {
    @XmlElement(name = "id")
    private String id;

    @XmlElement(name = "version")
    private String version;

    public EntityVersionInfo() {
        //no arg constructor
    }

    //GETTERS AND SETTERS
}

Answer 1

Adding this to EntityVersionInfo

@Override
public String toString() {
    return "EntityVersionInfo [id=" + id + ", version=" + version + "]";
}

Adding this to TopLevelObject

@Override
public String toString() {
    return "TopLevelObject [versionInfo=" + versionInfo + "]";
}

Running this test I get:

    JAXBContext context = JAXBContext.newInstance(TopLevelObject.class);
    Unmarshaller u = context.createUnmarshaller();

    Reader reader = new StringReader(
            "<topLevelObject>\r\n" + 
            "  <entityVersionInfo>\r\n" + 
            "        <id>111111</id>\r\n" + 
            "        <version>1</version>\r\n" + 
            "  </entityVersionInfo>\r\n" + 
            "</topLevelObject>");
    Object o = u.unmarshal(new InputSource(reader ));
    System.out.println(o);

I get :

TopLevelObject [versionInfo=EntityVersionInfo [id=111111, version=1]]

So your entity code is good, maybe you have more then one EntityVersionInfo class in your project or something else, but entities are good.