The contract is defined by wsdl and schema, not by java. The way you should examine this, is:

1) look at the wsdl to see what schema type is used for the return
2) look at jaxrpc-mapping to see waht java type this maps to

If that is the base type, then only the SOAP representation of the base type will be put on the wire and the client will get the base type regardless of whether you returned the sub type from your endpoint.

If wsdl, schema and mapping use the sub type instead of the basetype, we have a bug need to create a jira issue for it.

You can use the 'code' marker

 <some-element>text</some-element>

I'm not the original author, but I'm having the same problem:

In responses generated by JBoss hosted web services, the returned document does not properly identify the derived type with an xsi:type attribute when the service is defined to return an instance of the super type.

Thomas, I've checked and included everything you asked the original poster for, and using your criteria, must conclude this is a JBoss bug.

Environment: JBoss 4.0.2, Windows XP, Doc-Literal, JWSDP 1.6, top-down development, one part per message

Below I give an example of the incorrect instance doc returned by JBoss, my WSDL, fragments of the type mapping, the SEI and the SEI implementation.

 <?xml version="1.0" encoding="UTF-8"?>
 <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <soapenv:Body>
 <ns1:result xmlns:ns1="http://siterefresh.refreshsoftware.com/types">
 <id>4FDB5C620016F617010582DF2C9A47A4</id>
 </ns1:result>
 </soapenv:Body>
 </soapenv:Envelope>

<definitions
 targetNamespace="http://siterefresh.refreshsoftware.com/wsdl/services"
 xmlns:tns="http://siterefresh.refreshsoftware.com/wsdl/services"
 xmlns:srt="http://siterefresh.refreshsoftware.com/types"
 xmlns="http://schemas.xmlsoap.org/wsdl/"
 xmlns:soapbind="http://schemas.xmlsoap.org/wsdl/soap/"
 name="SiteRefreshSoapServices">

 <types>
 <schema
 targetNamespace="http://siterefresh.refreshsoftware.com/types"
 xmlns="http://www.w3.org/2001/XMLSchema"
 xmlns:srt="http://siterefresh.refreshsoftware.com/types">

 <element name="event" type="srt:Event" />
 <element name="eventException" type="srt:EventException" />
 <element name="result" type="srt:Result" />

 <complexType name="Event" abstract="true">
 <sequence>
 <element name="id" type="string" minOccurs="0" />
 </sequence>
 </complexType>

 <complexType name="AssetRead">
 <complexContent>
 <extension base="srt:Event" />
 </complexContent>
 </complexType>

 <complexType name="AssetCreate">
 <complexContent>
 <extension base="srt:Event">
 <sequence>
 <element name="nextStep" type="int" />
 <element name="template" type="string" />
 </sequence>
 </extension>
 </complexContent>
 </complexType>

 <complexType name="Result" abstract="true"></complexType>

 <complexType name="AssetCreateResult">
 <complexContent>
 <extension base="srt:Result">
 <sequence>
 <element name="id" type="string" />
 </sequence>
 </extension>
 </complexContent>
 </complexType>

 <complexType name="AssetReadResult">
 <complexContent>
 <extension base="srt:Result">
 <sequence>
 <element name="id" type="string" />
 <element name="body" type="string" />
 </sequence>
 </extension>
 </complexContent>
 </complexType>

 <complexType name="EventException">
 <sequence>
 <element name="message" type="string" />
 </sequence>
 </complexType>

 </schema>
 </types>

 <message name="processEventResponse">
 <part name="processEventResponse" element="srt:result" />
 </message>
 <message name="processEventRequest">
 <part name="processEventRequest" element="srt:event" />
 </message>
 <message name="processEventException">
 <part name="processEventException" element="srt:eventException" />
 </message>

 <portType name="ServiceFacadeEndpoint">
 <operation name="processEvent">
 <input message="tns:processEventRequest"
 name="processEventRequest" />
 <output message="tns:processEventResponse"
 name="processEventResponse" />
 <fault message="tns:processEventException"
 name="processEventException" />
 </operation>
 </portType>

 <binding name="ServiceFacadeSoapBinding"
 type="tns:ServiceFacadeEndpoint">
 <soapbind:binding style="document"
 transport="http://schemas.xmlsoap.org/soap/http" />

 <operation name="processEvent">
 <soapbind:operation soapAction="" />
 <input name="processEventRequest">
 <soapbind:body use="literal" />
 </input>
 <output name="processEventResponse">
 <soapbind:body use="literal" />
 </output>
 <fault name="processEventException">
 <soapbind:fault name="processEventException"
 use="literal" />
 </fault>
 </operation>
 </binding>

 <service name="ServiceFacade">
 <port binding="tns:ServiceFacadeSoapBinding"
 name="ServiceFacadePort">
 <soapbind:address location="http://dummy-location" />
 </port>
 </service>

</definitions>

<?xml version="1.0" encoding="UTF-8"?>
<java-wsdl-mapping xmlns="http://java.sun.com/xml/ns/j2ee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.1"
 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://www.ibm.com/webservices/xsd/j2ee_jaxrpc_mapping_1_1.xsd">
 <package-mapping>
 <package-type>
 com.refreshsoftware.siterefresh.services.documents
 </package-type>
 <namespaceURI>
 http://siterefresh.refreshsoftware.com/wsdl/services
 </namespaceURI>
 </package-mapping>
 <package-mapping>
 <package-type>
 com.refreshsoftware.siterefresh.services.documents
 </package-type>
 <namespaceURI>
 http://siterefresh.refreshsoftware.com/types
 </namespaceURI>
 </package-mapping>

 <java-xml-type-mapping>
 <java-type>
 com.refreshsoftware.siterefresh.services.documents.Event
 </java-type>
 <root-type-qname
 xmlns:typeNS="http://siterefresh.refreshsoftware.com/types">
 typeNS:Event
 </root-type-qname>
 <qname-scope>complexType</qname-scope>
 <variable-mapping>
 <java-variable-name>id</java-variable-name>
 <xml-element-name>id</xml-element-name>
 </variable-mapping>
 </java-xml-type-mapping>

 <java-xml-type-mapping>
 <java-type>
 com.refreshsoftware.siterefresh.services.documents.AssetCreate
 </java-type>
 <root-type-qname
 xmlns:typeNS="http://siterefresh.refreshsoftware.com/types">
 typeNS:AssetCreate
 </root-type-qname>
 <qname-scope>complexType</qname-scope>
 <variable-mapping>
 <java-variable-name>nextStep</java-variable-name>
 <xml-element-name>nextStep</xml-element-name>
 </variable-mapping>
 <variable-mapping>
 <java-variable-name>template</java-variable-name>
 <xml-element-name>template</xml-element-name>
 </variable-mapping>
 </java-xml-type-mapping>

 <java-xml-type-mapping>
 <java-type>
 com.refreshsoftware.siterefresh.services.documents.Result
 </java-type>
 <root-type-qname
 xmlns:typeNS="http://siterefresh.refreshsoftware.com/types">
 typeNS:Result
 </root-type-qname>
 <qname-scope>complexType</qname-scope>
 </java-xml-type-mapping>

 <java-xml-type-mapping>
 <java-type>
 com.refreshsoftware.siterefresh.services.documents.AssetCreateResult
 </java-type>
 <root-type-qname
 xmlns:typeNS="http://siterefresh.refreshsoftware.com/types">
 typeNS:AssetCreateResult
 </root-type-qname>
 <qname-scope>complexType</qname-scope>
 <variable-mapping>
 <java-variable-name>id</java-variable-name>
 <xml-element-name>id</xml-element-name>
 </variable-mapping>
 </java-xml-type-mapping>

 <java-xml-type-mapping>
 <java-type>
 com.refreshsoftware.siterefresh.services.documents.EventException_Exception
 </java-type>
 <root-type-qname
 xmlns:typeNS="http://siterefresh.refreshsoftware.com/types">
 typeNS:EventException
 </root-type-qname>
 <qname-scope>complexType</qname-scope>
 <variable-mapping>
 <java-variable-name>message</java-variable-name>
 <xml-element-name>message</xml-element-name>
 </variable-mapping>
 </java-xml-type-mapping>
 <exception-mapping>
 <exception-type>
 com.refreshsoftware.siterefresh.services.documents.EventException_Exception
 </exception-type>
 <wsdl-message
 xmlns:exMsgNS="http://siterefresh.refreshsoftware.com/wsdl/services">
 exMsgNS:processEventException
 </wsdl-message>
 <constructor-parameter-order>
 <element-name>message</element-name>
 </constructor-parameter-order>
 </exception-mapping>

 <service-interface-mapping>
 <service-interface>
 com.refreshsoftware.siterefresh.services.documents.ServiceFacade
 </service-interface>
 <wsdl-service-name
 xmlns:serviceNS="http://siterefresh.refreshsoftware.com/wsdl/services">
 serviceNS:ServiceFacade
 </wsdl-service-name>
 <port-mapping>
 <port-name>ServiceFacadePort</port-name>
 <java-port-name>ServiceFacadePort</java-port-name>
 </port-mapping>
 </service-interface-mapping>

 <service-endpoint-interface-mapping>
 <service-endpoint-interface>
 com.refreshsoftware.siterefresh.services.documents.ServiceFacadeEndpoint
 </service-endpoint-interface>
 <wsdl-port-type
 xmlns:portTypeNS="http://siterefresh.refreshsoftware.com/wsdl/services">
 portTypeNS:ServiceFacadeEndpoint
 </wsdl-port-type>
 <wsdl-binding
 xmlns:bindingNS="http://siterefresh.refreshsoftware.com/wsdl/services">
 bindingNS:ServiceFacadeSoapBinding
 </wsdl-binding>
 <service-endpoint-method-mapping>
 <java-method-name>processEvent</java-method-name>
 <wsdl-operation>processEvent</wsdl-operation>
 <method-param-parts-mapping>
 <param-position>0</param-position>
 <param-type>
 com.refreshsoftware.siterefresh.services.documents.Event
 </param-type>
 <wsdl-message-mapping>
 <wsdl-message
 xmlns:wsdlMsgNS="http://siterefresh.refreshsoftware.com/wsdl/services">
 wsdlMsgNS:processEventRequest
 </wsdl-message>
 <wsdl-message-part-name>
 processEventRequest
 </wsdl-message-part-name>
 <parameter-mode>IN</parameter-mode>
 </wsdl-message-mapping>
 </method-param-parts-mapping>
 <wsdl-return-value-mapping>
 <method-return-value>
 com.refreshsoftware.siterefresh.services.documents.Result
 </method-return-value>
 <wsdl-message
 xmlns:wsdlMsgNS="http://siterefresh.refreshsoftware.com/wsdl/services">
 wsdlMsgNS:processEventResponse
 </wsdl-message>
 <wsdl-message-part-name>
 processEventResponse
 </wsdl-message-part-name>
 </wsdl-return-value-mapping>
 </service-endpoint-method-mapping>
 </service-endpoint-interface-mapping>
</java-wsdl-mapping>

public interface ServiceFacadeEndpoint extends Remote {
 Result processEvent(Event event) throws EventException_Exception, java.rmi.RemoteException;
}

 public Result processEvent(Event event) throws EventException_Exception {

 Result res = null;

 log.info("got an event: " + event.getClass().getName());

 if (event instanceof AssetCreate) {
 res = new AssetCreateResult();
 ((AssetCreateResult)res).setId("123");
 }

 return res;
 }

This has been assigned to
http://jira.jboss.org/jira/browse/JBWS-349