Class Cast Exception when trying to unmarshall xml?

Question

Trying to get past a class cast exception here:

FooClass fooClass = (FooClass ) unmarshaller.unmarshal(inputStream);

throws this exception:

java.lang.ClassCastException: javax.xml.bind.JAXBElement

I don't understand this - as the class was generated by the xjc.bat tool - and the classes it generated I have not altered at all - so there should be no casting problems here - the unmarshaller should really be giving me back a class that CAN be cast to FooClass.

Any ideas as to what I am doing wrong?

user_22656 · Answer

Does FooClass have the XmlRootElement annotation? If not, try:

Source source = new StreamSource(inputStream);
JAXBElement root = unmarshaller.unmarshal(source, FooClass.class);
FooClass foo = root.getValue();

That's based on the Unofficial JAXB Guide.

Simon_E_5175 · Answer

For a fuller explanation read this article. It turns out that your XSD must be properly set up, i.e. there must be some root element encompassing all the other elements.

XJC does try to put @XmlRootElement annotation on a class that we generate from a complex type. The exact condition is somewhat ugly, but the basic idea is that if we can statically guarantee that a complex type won't be used by multiple different tag names, we put @XmlRootElement.

user_212950 · Answer

We spent too many hours fidgeting with the JAXB factory class to satisfy the unmarshaller. We've learned that using the unmarshaller without calling the JAXB-generated object factory works alright. Hope the sample code redeems someone's frustration:

System.out.println("Processing generic-type unmarshaller: ");
MessageClass mcObject = unmarshalXml(MessageClass.class, msgQryStreamSource,
    NAMESPACE + "." + "MessageClass");

public static  T unmarshalXml(Class clazz, StreamSource queryResults,
    String contextNamespace)
    {
        T resultObject = null;
        try {
            //Create instance of the JAXBContext from the class-name
            JAXBContext jc;
            jc = JAXBContext.newInstance(Class.forName(clazz.getName()));
            Unmarshaller u = jc.createUnmarshaller();
            resultObject = clazz.cast(u.unmarshal(queryResults));
            }
              //Put your own error-handling here.
        catch(JAXBException e)
        {
            e.printStackTrace();
        }
        catch (ClassCastException e)
        {
            e.printStackTrace();
        }
        catch (ClassNotFoundException e)
        {
            e.printStackTrace();
        }
        return clazz.cast(resultObject);
    }

TofuBeer_65868 · Answer

I'd look at the XML file and make sure it is roughly what you expect to see.

I'd also temporarily change the code to:

Object o = unmarshaller.unmarshal(inputStream);
System.out.println(o.getClass());

If the first one failes then the class cast is happening inside the unmarshal method, if it succeeds then you can see the actual class that you are getting back and then figure out why it isn't what you expect it to be.

Greg_Noe_85711 · Answer

Are you absolutely sure FooClass is the root element of the xml input source you passed it? Unmarshall will return an object of the root element created by xjc.

user_1719312 · Answer

If you have access and you can modify the XSD. For me, this issue appends when I generate the XSD from XML with IDEA.

With this xml :

IDEA generate an XSD like that and JAXB won't generate an root element :

BUT, if you modify the XSD in this way (modify your root element "schema" in order to get the xs:complexType inside the tag xs:element) :

JAXB will generate the root element !

user_9346778 · Answer

In my case, I get the error when trying to send a soap petition from the SOAPUI application. I need to set the property 'strip whitespaces' to true to skip this error.

When debug the content received, is a list with the next content:

[0] = "
"
[1] = JAXBElement
[2] = "
"

Hope help someone.

Class Cast Exception when trying to unmarshall xml?

14 Answers