How to define the HTTP Response content with the HttpGateway in JBoss SOA-P 5?

Issue

There is a synchronous HttpGateway action. When trying to control the html returned it is not obvious how to do this. Looking at the documentation it appears it can be done:

    HttpResponse responseInfo = new HttpResponse(HttpServletResponse.SC_OK);

    responseInfo.setContentType("text/xml");
    // Set other response info ...

    // Set the HttpResponse instance on the ESB response Message instance
    responseInfo.setResponse(responseMessage);

But when the HttpResponse class is examined, it is not seen how to set the html.