Jasper 报告 - 如果列表组件没有返回值则打印子报告

Question

我有一份报告，其中有一个主报告和一个子报告。

在子报表中，我有一个列表组件，我在其中显示来自子数据集的 xml 路径数据。

但有时我从该 xml 路径中得不到任何数据。

在那种情况下，我想用另一个数据源（DB数据源）调用子报表。

这可能吗？

<subDataset name="pageHeader" uuid="cf87fcbb-cbcd-4c3b-bf87-3cf147854adb">
    <property name="com.jaspersoft.studio.data.defaultdataadapter" value="Sample DB"/>
    <queryString language="xPath">
        <![CDATA[//address]]>
    </queryString>
    <field name="name" class="java.lang.String">
        <property name="net.sf.jasperreports.xpath.field.expression" value="name"/>
        <fieldDescription><![CDATA[name]]></fieldDescription>
    </field>
    <field name="streetAdressOne" class="java.lang.String">
        <property name="net.sf.jasperreports.xpath.field.expression" value="streetAdressOne"/>
        <fieldDescription><![CDATA[streetAdressOne]]></fieldDescription>
    </field>
    <field name="cityCode" class="java.lang.String">
        <property name="net.sf.jasperreports.xpath.field.expression" value="cityCode"/>
        <fieldDescription><![CDATA[cityCode]]></fieldDescription>
    </field>
    <field name="city" class="java.lang.String">
        <property name="net.sf.jasperreports.xpath.field.expression" value="city"/>
        <fieldDescription><![CDATA[city]]></fieldDescription>
    </field>
</subDataset>
<componentElement>
    <reportElement key="" positionType="Float" stretchType="RelativeToTallestObject" x="0" y="70" width="210" height="100" isRemoveLineWhenBlank="true" uuid="fc7d22c7-8c60-4ecb-974f-c842becc4bf7">
        <property name="com.jaspersoft.studio.layout" value="com.jaspersoft.studio.editor.layout.FreeLayout"/>
        <property name="net.sf.jasperreports.export.headertoolbar.table.name" value=""/>
    </reportElement>
    <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" printOrder="Vertical">
        <datasetRun subDataset="pageHeader" uuid="1e20fa2b-bb3a-475f-b721-5a13d3c374eb">
            <datasetParameter name="XML_DATE_PATTERN">
                <datasetParameterExpression><![CDATA[$P{XML_DATE_PATTERN}]]></datasetParameterExpression>
            </datasetParameter>
            <datasetParameter name="XML_NUMBER_PATTERN">
                <datasetParameterExpression><![CDATA[$P{XML_NUMBER_PATTERN}]]></datasetParameterExpression>
            </datasetParameter>
            <datasetParameter name="XML_LOCALE">
                <datasetParameterExpression><![CDATA[$P{XML_LOCALE}]]></datasetParameterExpression>
            </datasetParameter>
            <datasetParameter name="XML_TIME_ZONE">
                <datasetParameterExpression><![CDATA[$P{XML_TIME_ZONE}]]></datasetParameterExpression>
            </datasetParameter>
            <dataSourceExpression><![CDATA[((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("//buyer/address")]]></dataSourceExpression>
        </datasetRun>
        <jr:listContents height="100" width="210">
            <frame>
                <reportElement x="0" y="0" width="210" height="70" isRemoveLineWhenBlank="true" uuid="86749038-19ba-43c7-bc23-bb9e7cd08f11"/>
                <textField textAdjust="StretchHeight">
                    <reportElement stretchType="RelativeToTallestObject" x="0" y="0" width="210" height="20" uuid="eac696b9-e20f-48a3-b70d-b186f5e649d6"/>
                    <textFieldExpression><![CDATA[$F{name}]]></textFieldExpression>
                </textField>
                <textField>
                    <reportElement stretchType="ContainerHeight" x="0" y="30" width="210" height="20" uuid="2af38c05-8736-49f3-b384-277d8debac61"/>
                    <textFieldExpression><![CDATA[IF($F{streetAdressOne}  != null, $F{streetAdressOne} , "")]]></textFieldExpression>
                </textField>
                <textField>
                    <reportElement x="0" y="50" width="210" height="20" uuid="188ade32-a151-4d95-b89c-9b1d9da61156"/>
                    <textFieldExpression><![CDATA[$F{cityCode} + " " + $F{city}]]></textFieldExpression>
                </textField>
            </frame>
            <subreport>
                <reportElement x="0" y="0" width="210" height="100" uuid="b7174033-6102-4fde-a55c-2fc912c29fad"/>
                <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.JREmptyDataSource()]]></dataSourceExpression>
                <subreportExpression><![CDATA["Buyer.jasper"]]></subreportExpression>
            </subreport>
        </jr:listContents>
    </jr:list>
</componentElement>