How to format numeric data in Excel

We can use net.sf.jasperreports.export.xls.detect.cell.type property for solving issue.

The quote from documentation:

net.sf.jasperreports.export.xls.detect.cell.type

Property whose value is used as default state of the IS_DETECT_CELL_TYPE export flag.

Specifies whether the exporter should take into consideration the type of the original text field expressions and set the cell types and values accordingly.

For example we can set this property for the whole report:

<?xml version="1.0" encoding="UTF-8"?>
<jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" ...>
    <property name="net.sf.jasperreports.export.xls.detect.cell.type" value="true"/>