Using subreports

Parameters#

Parameter	Details
parametersMapExpression	The Map with parameters. Not required
subreportParameter	The pair of name and value (set with subreportParameterExpression). Not required. Several parameters can be passed to subreport
connectionExpression	Connection for getting data. Not required
dataSourceExpression	Expression for passing Datasource. Not required
subreportExpression	The subreport’s path/URI or even JasperReport object. Not required
returnValue	The pair of name and value. Not required. Several values can be returned from subreport to master report back

Remarks#

Subreports can be used for constructing complex reports. The reusing of existing reports is another goal of using subreports.
The subreport will be shown as a part of master report in case using of <subreport> element.
The value of subreportExpression parameter is differ for using at JasperReports Server or just by JasperReports framework (some API using or using in IDE).

For JasperReports Server it looks like:
```
<subreportExpression><![CDATA["repo:subreport.jrxml"]]></subreportExpression>
```
For using by just JasperReports engine:
```
<subreportExpression><![CDATA["/somePath/subreport.jasper"]]></subreportExpression>
```
^{The great explanation by @AndreasDietrich can be found at JasperServer: Unable to locate the subreport exception post}
For some reasons the subreport can be used as a common report - without calling from the master report (with help of <subreport> element). The subreport is always a report.

Passing connection to subreport; return values back to the master report

This is a snippet of master report. Two parameters and the connection (for example, jdbc) are passing to the subreport. One value is returned from the subreport back to the master report, this value (variable) can be used in master report

<subreport>
    <reportElement x="0" y="80" width="200" height="100"/>
    <subreportParameter name="someSubreportParameter">
        <subreportParameterExpression><![CDATA[$P{someMasterReportParamter}]]></subreportParameterExpression>
    </subreportParameter>
    <subreportParameter name="anotherSubreportParameter">
        <subreportParameterExpression><![CDATA["Some text - constant value"]]></subreportParameterExpression>
    </subreportParameter>
    <connectionExpression><![CDATA[$P{REPORT_CONNECTION}]]></connectionExpression>
    <returnValue subreportVariable="someVariableInSubreport" toVariable="someVariableInMasterReport"/>
    <subreportExpression><![CDATA["$P{SUBREPORT_DIR} + "subreport.jasper"]]></subreportExpression>
</subreport>

Passing datasoure to subreport

This is a snippet of master report. The datasource is passed to the subreport with help of net.sf.jasperreports.engine.data.JRBeanCollectionDataSource constructor

<field name="someFieldWithList" class="java.util.List"/>
<!-- ...... -->
<subreport>
    <reportElement x="0" y="0" width="200" height="70"/>
    <parametersMapExpression><![CDATA[$P{REPORT_PARAMETERS_MAP}]]></parametersMapExpression>
    <dataSourceExpression><![CDATA[net.sf.jasperreports.engine.data.JRBeanCollectionDataSource($F{someFieldWithList})]]></dataSourceExpression>
    <subreportExpression><![CDATA[$P{SUBREPORT_DIR} + "subreport.jasper"]]></subreportExpression>
</subreport>