Nor any of its super class is known to this context

I'm trying to send some entity to ejb based web service. Here is my web service client code:

package ejbserviceclient;

import java.net.MalformedURLException;
import java.net.URL;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.namespace.QName;
import javax.xml.ws.Service;

public class EjbServiceClient {

  public static void main(String[] args) throws MalformedURLException, JAXBException {

    JAXBContext context = JAXBContext.newInstance(EjbServiceClient.class);


    URL url = new URL("http://ipsedin:8080/WebServiceBeanService/WebServiceBean?wsdl");
    QName serviceName = new QName(
            "http://ejb.rpt.softcomputer.com/",
            "WebServiceBeanService");
    QName portName = new QName(
            "http://ejb.rpt.softcomputer.com/",
            "WebServiceBeanPort");

    Service service = Service.create(url, serviceName);
    Echo ejbService = service.getPort(portName, Echo.class);

    System.out.println(ejbService.echo("lololo"));
    System.out.println(ejbService.processExCourse(new ExCourse()));

  }
}

And here is entity:

package ejbserviceclient;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class ExCourse {

int id;

}

But there is exception:

Exception in thread "main" javax.xml.ws.WebServiceException: javax.xml.bind.MarshalException
 - with linked exception:
[javax.xml.bind.JAXBException: class ejbserviceclient.ExCourse nor any of its super class is known to this context.]
    at com.sun.xml.internal.ws.message.jaxb.JAXBMessage.writePayloadTo(JAXBMessage.java:318)
    at com.sun.xml.internal.ws.message.AbstractMessageImpl.writeTo(AbstractMessageImpl.java:131)
    at com.sun.xml.internal.ws.encoding.StreamSOAPCodec.encode(StreamSOAPCodec.java:98)
    at com.sun.xml.internal.ws.encoding.SOAPBindingCodec.encode(SOAPBindingCodec.java:249)
    at com.sun.xml.internal.ws.transport.http.client