Need to manually add xsi namespace to SOAP envelope

My project is using inheritance to define some types used in WS requests and that's causing some unexpected trouble. Here is a simplified version of my project:

The base class:

@XmlType(name = "BaseClass")
@XmlSeeAlso( {ExtendingClass1.class, ExtendingClass2.class} )
class BaseClass {....}

The extending class is like this:

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "extendingClass1", propOrder = { "foo" })
@XmlRootElement(name = "extendingClass1")
public class ExtendingClass1 extends BaseClass {....}

The request looks like this:

@XmlAccessorType(XmlAccessType.FIELD)
class Request {
  @XmlElementRefs({ @XmlElementRef(type = ExtendingClass1.class), @XmlElementRef(type = ExtendingClass2.class) })
   protected BaseClass myObject;
}

When SOAPUI creates the request for me, I need to manually add to the envelope the namespace:
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

And I need to change the requests a bit to add xsi:type to my objects. For example:
<myns:myObject xsi:type="myns:ExtendingClass1">

Even though I have google'd for a while and looked up in the forum, I haven't been able to find a proper solution for this. So here are my questions:

• Is there a way I can tell SOAPUI to automatically add this namespace?


• Do I need to change my web service code to force the addition of the namespace on the envelope?


• Other devs in the project complain that they need to manually add the namespace and type to attributes, is there any way that SOAPUI can help with this?

I appreciate your help and support!