List deeply nested set in jasper report

Question

I have deep nested Set of strings in my model and I can't list them in my jasper report.

My model:

Profile:
List<Project> projectList;

    Project:
    Skill skills;

          Skill:
          Set<String> programmingLanguages;

I create report where Profile is main report, Skill is subreport but I can't get data from programmingLanguages Set in Skill subreport.

My jrxml files:

Profile report

<?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="jasper-test" pageWidth="595" pageHeight="842" columnWidth="535" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20" uuid="9f3515b2-a9bf-4194-ae0f-ceb8d4de1e70">
<parameter name="SUBREPORT_DIR" class="java.lang.String" isForPrompting="false"/>
  <field name="projectList" class="java.util.List"/>
<detail>
<band height="299" splitType="Stretch">
<subreport>
                <reportElement x="-2" y="148" width="555" height="51" uuid="f081f980-ea14-4434-9282-beebf515cb6c"/>
                <subreportParameter name="SUBREPORT_DIR"/>
                <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.data.JRBeanCollectionDataSource
                    ($F{projectList})]]></dataSourceExpression>
                <subreportExpression><![CDATA[$P{SUBREPORT_DIR} + "jasper-subreport-project.jasper"]]></subreportExpression>
</subreport>
</band> 

</detail>
</jasperReport>

Project subreport:

<?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="jasper-test" pageWidth="595" pageHeight="842" columnWidth="535" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20" uuid="9f3515b2-a9bf-4194-ae0f-ceb8d4de1e70">
<field name="skills" class="com.company.profilelist.model.Skill"/>
<detail>
<band height="299" splitType="Stretch">
    <subreport>
                <reportElement x="296" y="43" width="200" height="100" uuid="1084d612-8188-4dcc-8b09-6e534e76b879"/>
                <subreportParameter name="skills">
                    <subreportParameterExpression><![CDATA[$F{skills}]]></subreportParameterExpression>
                </subreportParameter>
                 <subreportExpression><![CDATA[$P{SUBREPORT_DIR} + "jasper-subreport-skills.jasper"]]></subreportExpression>
            </subreport>
</band> 

</detail>
</jasperReport>

Skill subreport:

<?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="jasper-test" pageWidth="595" pageHeight="842" columnWidth="535" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20" uuid="9f3515b2-a9bf-4194-ae0f-ceb8d4de1e70">
<field name="programmingLanguages" class="java.util.Set">
<detail>
<band height="299" splitType="Stretch">
    <textField>
                <reportElement x="100" y="20" width="119" height="23" uuid="085d4a07-8dfa-4de4-b89d-6d915681fbc5"/>
                <textElement>
                    <font size="9"/>
                </textElement>
                <textFieldExpression><![CDATA[$F{programmingLanguages}]]></textFieldExpression>
            </textField>
</band> 

</detail>
</jasperReport>

I can't reach programmingLanguage field in skills subreport is there something I'm missing ?

Answer 1

try with following steps,

firstly, declare the skills as a List in the project model

Project:
List<Skill> skills;

then, change the class of field skills to java.util.List in the project report

<field name="skills" class="java.util.List"/>

finally, add dataSourceExpression for skill sub report in the project report and remove the subreportParameterExpression of skill sub report in the project report

<subreport>
    <reportElement x="296" y="43" width="200" height="100" uuid="1084d612-8188-4dcc-8b09-6e534e76b879"/>
    <subreportParameter name="skills"/>
    <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.data.JRBeanCollectionDataSource($F{skills})]]></dataSourceExpression>                
    <subreportExpression><![CDATA[$P{SUBREPORT_DIR} + "jasper-subreport-skills.jasper"]]></subreportExpression>
</subreport>

Answer 2

You can build a java Object that suits your DataSource exactly and a second which shows all your needed variables in a not nested form and then write a Datamodel-MergeClass. It works great for me.