We had the same problem, and we did not find a solution, just ugly workarounds.
, , .
, . :
$P{field_name1} | $P{field_name2}
------
$F{value1} | $P{value2} ...
. , , . , , .
: Jasper Design ( , ) - jrxml, .
JasperDesign jasperDesign = JRXmlLoader.load(myJrxml);