Java 如何向soap头添加属性？

我想向soap头添加属性，如

    <soapenv:Header attr="somevalue"attr1="somevalue"/> 

    <soapenv:Header>
        <soapenv:Header attr="somevalue"attr1="somevalue"/>
    </soapenv:Header>

SOAPFactory factory = SOAPFactory.newInstance();
String prefix = "soapenv";
String uri="http://schemas.xmlsoap.org/soap/envelope/";
SOAPElement Elem;
Elem = factory.createElement("Header",prefix,uri);
Elem.addAttribute(QName.valueOf("attr"), "value");
Elem.addAttribute(QName.valueOf("attr"), "value");
SOAPHeaderElement soapheader=new SOAPHeaderElement(Elem);
stub.setHeader(soapheader);