jsonql datasource reference This page has a good comparison for syntax and capability of JSON and JSONQL. In question (with language="json") the proper field definition will looks like this: <field name="KeyTwoValue" class="java.lang.String"> <property name="net.sf.jasperreports.json.field.expression" value="proposalFees.nodes(type == KEY_2).value[0]"/> </field>[/code]