When defining a field in Jasper, normally you would supply the RecordEditor field name in the fieldDescription tag as below.
In the following code, the Jasper field PackQty is associated with the RecordEditor field Pack Qty.
25: <field name="PackQty" class="java.math.BigDecimal"> 26: <fieldDescription><![CDATA[Pack Qty]]></fieldDescription> 27: </field>
When the Jasper field name is the same as the RecordEditor field you do not need to use the fieldDescription tag as below.
34: <field name="Apn" class="java.lang.String"> 35: </field>
For files with more than one type of Record the RecordDataSource stores the last Line of each Record Type for your use. You can access a field in a specific record by using a field name of Record Name.Field Name. i.e. The following example accesses the field beg01 code in the last ams PO Download: Header Line:
62: <field name="Beg01Code" class="java.lang.String"> 63: <fieldDescription><![CDATA[ams PO Download: Header.beg01 code]]></fieldDescription> 64: </field>