JRExporter became deprecated in 5.6. They introduced new interface Exporter and retrofitted all exporters to have ExporterInput, ReportExportConfiguration, ExporterConfiguration,ExporterOutput. See below link
http://jasperreports.sourceforge.net/api/net/sf/jasperreports/export/Exporter.html
This means that instead of setParameter, you need to create configuration using above mentioned classes or their child classes
PDF export example. Excel export should follow same methodology
JRPdfExporter exporter = new JRPdfExporter();
exporter.setExporterInput(new SimpleExporterInput(jasperPrint));
exporter.setExporterOutput(outputStream);
SimplePdfExporterConfiguration configuration = new SimplePdfExporterConfiguration();
exporter.setConfiguration(configuration);
exporter.exportReport();
Excel counterpart
JRXlsExporter exporter = new JRXlsExporter();
exporter.setExporterInput(new SimpleExporterInput(jasperPrint));
exporter.setExporterOutput(new SimpleOutputStreamExporterOutput(destFile));
SimpleXlsReportConfiguration configuration = new SimpleXlsReportConfiguration();
configuration.setOnePagePerSheet(true);
configuration.setDetectCellType(true);
configuration.setCollapseRowSpan(false);
exporter.setConfiguration(configuration);
exporter.exportReport();
SimpleXlsReportConfiguration will have excel export related configuration. Set values as per your requirement