reqEnv.declareNamespace("http://schemas.xmlsoap.org/wsdl/soap12/","soap12");
SOAPHeader header = omfactory.createSOAPHeader(reqEnv);
OMNamespace hns = reqEnv.declareNamespace("http://soapinterop.org/echoheader/", "hns"); //xmlns:m0="http://soapinterop.org/echoheader/
SOAPHeaderBlock block2 = header.addHeaderBlock("echoMeStructRequest", hns);
block2.addAttribute("xsi:type", "s:SOAPStruct", null);
OMElement h2Val1 = omfactory.createOMElement("varString", null);
h2Val1.addAttribute("xsi:type", "xsd:string", null);
h2Val1.addChild(omfactory.createText("string"));