SoapUi Groovy conditional property transfer

smilnik 

There is another approach which finds offer id for matching service def and doesn't use xpath.  You may use which ever is comfortable for you.

NOTE: have used context.response as place holder value for xml data which inside parseText(), feel free to change as needed. 

Follow the comments in-line.

//Define the match / search criteria, element name and value 
def match = [ key:'ServiceDefinitionRefID',value:'SRV-SAF']

//Find all OfferItem 's
def oItems = new XmlSlurper().parseText(context.response).'**'.findAll {it.name() == 'OfferItem'}

//Get the Offer Item Id by applying search criteria defined above in match variable, returns null if no match
def getOfferItemIdForMatchingElement = { oItem, name, value -> oItem.'**'.find { it.name() == name && it.text()==value } ? oItem.OfferItemID.text() : null }

//Get offer item id for all Offer items, of course, there will be one as we are expecting, so filter null values
def offerItemId = oItems.collect { oItem -> getOfferItemIdForMatchingElement (oItem, match['key'], match['value']) }.find {it}

log.info "Offer item id: $offerItemId"
assert !offerItemId, 'No offer item id found for defined match criteria'

context.testCase.setPropertyValue('ITEMID', offerItemId)