OpenSAML user discussion

Hi
I am implementing the webservice method which will take saml artifact and 
retireves the authentication assertion and retunr to the client calling as 
follows
public SAMLAssertion getSAMLAuhtenticationAssertion(String SAMLArt) throws 
AxisFault

but when i try to create webservice i got the following errors
<em>
The service class 
"com.tta.checkpoint.webservices.server.service.SAMLAssertionGenerationServiceImpl"
 does not comply to one or more requirements of the JAX-RPC 1.1 
specification, and may not deploy or function correctly.
  The value type "org.opensaml.SAMLObject" used via the service class 
"com.tta.checkpoint.webservices.server.service.SAMLAssertionGenerationServiceImpl"
 does not have a public default constructor. Chapter 5.4 of the JAX-RPC 1.1 
specification requires a value type to have a public default constructor, 
otherwise a JAX-RPC 1.1 compliant Web service engine may be unable to 
construct an instance of the value type during deserialization.
  The field or property "conditions" on the value type 
"org.opensaml.SAMLAssertion" used via the service class 
"com.tta.checkpoint.webservices.server.service.SAMLAssertionGenerationServiceImpl"
 has a data type, "java.util.Iterator", that is not supported by the JAX-RPC 
1.1 specification. Instances of the type may not serialize or deserialize 
correctly. Loss of data or complete failure of the Web service may result.
  The field or property "advice" on the value type 
"org.opensaml.SAMLAssertion" used via the service class 
"com.tta.checkpoint.webservices.server.service.SAMLAssertionGenerationServiceImpl"
 has a data type, "java.util.Iterator", that is not supported by the JAX-RPC 
1.1 specification. Instances of the type may not serialize or deserialize 
correctly. Loss of data or complete failure of the Web service may result.
  The field or property "statements" on the value type 
"org.opensaml.SAMLAssertion" used via the service class 
"com.tta.checkpoint.webservices.server.service.SAMLAssertionGenerationServiceImpl"
 has a data type, "java.util.Iterator", that is not supported by the JAX-RPC 
1.1 specification. Instances of the type may not serialize or deserialize 
correctly. Loss of data or complete failure of the Web service may result.
</em>

How do i return the SAMLassertion to client? what shud be my method signature?