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 block1 = header.addHeaderBlock("echoMeStringRequest", hns);
block1.addAttribute("xsi:type", "xsd:string", null);
block1.addChild(omfactory.createText("string"));
// header.addChild(headerChild);
header.addChild(block1);
SOAPHeaderBlock block2 = header.addHeaderBlock("echoMeStructRequest", hns);