iReport/jasperReports how can i check in xml data source if node exsicts

i new to iReport , my question is in the expression editor , how can i build expression that checks if xml node

extincts and base on that print string

i have this expression that returns me null in the result :

( $F{root_customer}.isEmpty() ? "Entity name:" :"Customer id:" )

the r开发者_如何转开发oot_customer does not exsict in the xml

Try something along the following lines in your expression.

( $F{root_customer} == null ? "Entity name:" + $F{someField}  
    :"Customer id:" +  + $F{root_customer})