I'm using Nested Java Collections to generate a report. I've managed to display a nested collection of my main objects as a table. Now I would like to display another level as a table within a table, but the engine throws an exception on this. The main java object contains a List-attribute named "interestingCases". And an InterestingCase object contains & List-attribute named "interestingCaseReasons". Can anyone tell me, if it possible to nest these tables and if so, what I'm doing wrong. Thanks in advance, Bart Code:<band height="72"> <componentElement> <reportElement key="table 8" style="table 8" x="0" y="32" width="555" height="20"/> <jr:table 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="InterestingCaseDataSet"> <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.data.JRBeanCollectionDataSource($F{interestingCases})]]></dataSourceExpression> </datasetRun> <jr:column width="90"> <jr:columnHeader style="table 8_CH" height="30" rowSpan="1"> <textField isStretchWithOverflow="true" isBlankWhenNull="true"> <reportElement x="0" y="0" width="90" height="30"/> <textElement/> <textFieldExpression class="java.lang.String"><![CDATA[$R{report.enquiry.table.interesting.case.header.reason}]]></textFieldExpression> </textField> </jr:columnHeader> <jr:detailCell style="table 8_TD" height="20" rowSpan="1"> <componentElement> <reportElement key="table 11" style="table 11" x="0" y="0" width="90" height="20"/> <jr:table> <datasetRun subDataset="InterestingCaseReasonDataSet"> <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.data.JRBeanCollectionDataSource($F{interestingCaseReasons})]]></dataSourceExpression> </datasetRun> <jr:column width="90"> <jr:detailCell style="table 11_TD" height="20"> <textField> <reportElement x="0" y="0" width="90" height="20"/> <textElement/> <textFieldExpression class="java.lang.String"><![CDATA[str($F{messageKey})]]></textFieldExpression> </textField> </jr:detailCell> </jr:column> </jr:table> </componentElement> </jr:detailCell> </jr:column> </jr:table> </componentElement> </band>