soaplogin.groovy

public static String buildSoapLogin(String username, String password) {
        def builder = new StreamingMarkupBuilder()
        builder.encoding = 'UTF-8'
        def soapEnv = builder.bind {
            mkp.xmlDeclaration()
            mkp.declareNamespace(soapenv: SOAP.SOAP11_NS)
            mkp.declareNamespace(tns: 'urn:partner.soap.sforce.com')
            mkp.declareNamespace(ens: 'urn:sobject.partner.soap.sforce.com')
            'soapenv:Envelope' {
                'soapenv:Header' {
                    if (sessionId) {
                        'tns:SessionHeader' {
                            'tns:sessionId' sessionId
                        }
                    }
                }
                'soapenv:Body' {
            'tns:login' {
                'tns:username' username
                'tns:password' password
            }
        }
            }
        }
        def writer = new StringWriter()
        soapEnv.writeTo(writer)
        return writer.toString()
    }