For excel to automatically detect what type of format the cell should be, add the following to your jrxml file at the top in the report properties section:
<property name="net.sf.jasperreports.export.xls.detect.cell.type" value="true"/>
For excel to automatically detect what type of format the cell should be, add the following to your jrxml file at the top in the report properties section:
<property name="net.sf.jasperreports.export.xls.detect.cell.type" value="true"/>