jasperreport生成pdf_jasperreport 导出excel_jasperreport json(66)

reporting engine will affect the java.util.Map object it receives, adding the built-in

report parameter values that correspond to the subreport. This map is also affected by the

individually specified subreport parameter values, as already explained above.

In order to avoid altering the original java.util.Map object that you send, you can wrap it

in a different map, before supplying it to the subreport filling process like this:

new HashMap(myOriginalMap)

This way, your original map object remains unaffected and modifications are made to the

wrapping map object.

This is useful especially when you want to supply to your subreport the same set of

parameters that the master report has received and you use the built-in

REPORT_PARAMETERS_MAP report parameter of the master report. However, you don't want

to affect the value of this built-in parameter and you will wrap it like this:

<parametersMapExpression>

new HashMap($P{REPORT_PARAMETERS_MAP})

</parametersMapExpression>

The JasperReports Ultimate Guide

Page 66

9.2 Subreport Data Source

Subreports need a data source in order to generate their content, just like normal report do.

In the 3.4 Filling Reports chapter of this book we have seen that when filling a report you have to

supply either a data source object or a connection object, depending on that particular report type. That

is if it has an internal SQL query and you want to have it executed to obtain the report data or you

supply the report data yourself.

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