JasperReports: JRDataSource.subDataSource shows undefined - jasper-reports

Question

I am following this tutorial to create my reports using iReport.
I have already created a couple of reports using the guidelines mentioned.
But in a new report, when I set the DataSource of the ListComponent Jasper reports the following error to me:
The method subDataSource(String) is undefined for the type JRDataSource                 value = ((net.sf.jasperreports.engine.JRDataSource)parameter_REPORT_DATA_SOURCE.getValue()).subDataSource("/items/invoices"); //$JR_EXPR_ID=11$
I tried to look up in the docs, It does mention that JRDataSource doesn't have any such methods. But, I have followed this tutorial earlier and made reports.
This is the JRXML code of the report where I am stuck:
<?xml version="1.0" encoding="UTF-8"?>
<jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" name="product-wise-sales-analysis" pageWidth="595" pageHeight="842" columnWidth="555" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20" uuid="a8a1a939-18a1-4ecf-8c4c-9f7b556b5ce3">
<property name="ireport.zoom" value="1.0"/>
<property name="ireport.x" value="0"/>
<property name="ireport.y" value="0"/>
<subDataset name="invoices" uuid="9d9c4386-0f01-4f9f-9b17-12906b566f63">
<queryString language="xPath">
<![CDATA[/data/items/invoices]]>
</queryString>
<field name="invoiceId" class="java.lang.String">
<fieldDescription><![CDATA[invoiceId]]></fieldDescription>
</field>
<field name="salesInvoiceDate" class="java.lang.String">
<fieldDescription><![CDATA[salesInvoiceDate]]></fieldDescription>
</field>
<field name="partyName" class="java.lang.String">
<fieldDescription><![CDATA[partyName]]></fieldDescription>
</field>
<field name="quantity" class="java.lang.String">
<fieldDescription><![CDATA[quantity]]></fieldDescription>
</field>
<field name="rate" class="java.lang.String">
<fieldDescription><![CDATA[rate]]></fieldDescription>
</field>
</subDataset>
<queryString language="xPath">
<![CDATA[/data/items]]>
</queryString>
<field name="productCatlgNo" class="java.lang.String">
<fieldDescription><![CDATA[productCatlgNo]]></fieldDescription>
</field>
<field name="description" class="java.lang.String">
<fieldDescription><![CDATA[description]]></fieldDescription>
</field>
<field name="groupName" class="java.lang.String">
<fieldDescription><![CDATA[groupName]]></fieldDescription>
</field>
<background>
<band splitType="Stretch"/>
</background>
<title>
<band height="79" splitType="Stretch"/>
</title>
<pageHeader>
<band height="35" splitType="Stretch"/>
</pageHeader>
<columnHeader>
<band height="23" splitType="Stretch">
<staticText>
<reportElement x="0" y="2" width="100" height="20" uuid="b14d57a3-c78e-4121-ac21-955b4ab431f0"/>
<text><![CDATA[productCatlgNo]]></text>
</staticText>
<staticText>
<reportElement x="147" y="2" width="100" height="20" uuid="c009d720-b224-4595-9761-89447d437dc3"/>
<text><![CDATA[description]]></text>
</staticText>
<staticText>
<reportElement x="341" y="0" width="100" height="20" uuid="f22f2f3f-885e-4ffd-bd2f-b69025a46c2d"/>
<text><![CDATA[groupName]]></text>
</staticText>
</band>
</columnHeader>
<detail>
<band height="34" splitType="Stretch">
<textField>
<reportElement x="147" y="0" width="194" height="12" uuid="383b8740-6b4d-4ddd-9e85-6aa45a08c464"/>
<textFieldExpression><![CDATA[$F{description}]]></textFieldExpression>
</textField>
<textField>
<reportElement x="0" y="0" width="147" height="12" uuid="ebd965f4-5684-49b8-8ed4-e11e43d64230"/>
<textFieldExpression><![CDATA[$F{productCatlgNo}]]></textFieldExpression>
</textField>
<textField>
<reportElement x="341" y="0" width="209" height="12" uuid="4b98a152-6c2e-4335-835a-9288c179df5a"/>
<textFieldExpression><![CDATA[$F{groupName}]]></textFieldExpression>
</textField>
<componentElement>
<reportElement x="0" y="12" width="555" height="21" uuid="786c54cf-6dc1-4daf-a174-694c24cfd27b"/>
<jr:list xmlns:jr="http://jasperreports.sourceforge.net/jasperreports/components" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports/components http://jasperreports.sourceforge.net/xsd/components.xsd">
<datasetRun subDataset="invoices" uuid="c61741af-4e58-4bb6-a18b-468a29c02b14">
<dataSourceExpression><![CDATA[$P{REPORT_DATA_SOURCE}.subDataSource("/items/invoices")]]></dataSourceExpression>
</datasetRun>
<jr:listContents height="21" width="555">
<textField>
<reportElement x="5" y="0" width="100" height="20" uuid="c3923524-ac87-4a59-a4d0-89d4c6ade197"/>
<textFieldExpression><![CDATA[$F{invoiceId}]]></textFieldExpression>
</textField>
</jr:listContents>
</jr:list>
</componentElement>
</band>
</detail>
<columnFooter>
<band height="45" splitType="Stretch"/>
</columnFooter>
<pageFooter>
<band height="54" splitType="Stretch"/>
</pageFooter>
<summary>
<band height="42" splitType="Stretch"/>
</summary>
</jasperReport>
Any ideas why this is happening?

Answer 1

I figured this out.
For some reason, I had to cast the DataSource of the ListComponent to a JRXmlDataSource object. (I haven't done this casting in my previous reports)
So the expression for DataSource in the ListComponent would be:
((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("/items/invoices")
instead of:
$P{REPORT_DATA_SOURCE}).subDataSource("/items/invoices")

Answer 2

In my case, the answer was to select "groovy" as the language used in the report.
Properties -> Report -> Language