OpenSAML user discussion

hi,
 i am using svn trunk code of opensaml, when i am trying to create a 
assertion and than print it. i am getting it as null

output: [saml:Asserton: null]
can you please help me what could be going wrong.

thanks
harsha


Configuration.init();
                XMLObjectBuilderFactory builderFactory = 
Configuration.getBuilderFactory();

  // Get the assertion builder based on the assertion element name
                AssertionBuilder builder = (AssertionBuilder) 
builderFactory.getBuilder(Assertion.DEFAULT_ELEMENT_NAME);
                  // Create the assertion
                Assertion assertion = builder.buildObject ();

      // set Id
                assertion.setID ("12345");
                IssuerBuilder ib = new IssuerBuilder();
        // set Issuer
                Issuer i = ib.buildObject();
                i.setValue("Hello World");
                assertion.setIssuer(i);
        // set IssueInstant
                DateTime dt = new DateTime();
                assertion.setIssueInstant(dt);
        // set Conditions
                ConditionsBuilder cb = new ConditionsBuilder();
                Conditions cd = cb.buildObject();
                cd.setNotOnOrAfter(dt);
                assertion.setConditions(cd);

        // set Subject

                 // Get the marshaller factory
  MarshallerFactory marshallerFactory = Configuration.getMarshallerFactory();

  // Get the Subject marshaller
  Marshaller marshaller = marshallerFactory.getMarshaller(assertion);

  // Marshall the Subject
  Element subjectElement = marshaller.marshall(assertion);
  System.out.println(subjectElement);