Large Excel JasperReports

When generating large Excel report by using JasperReports and DynamicJasper, have to take note the following configuration.

• Java Heap Size
• VIRTUALIZER
• IS_IGNORE_PAGINATION

If you miss 1 of the configuration, you might encounter OutOfMemoryError exception.

Check out the following example code.

public class JasperExcelReport {

protected JasperPrint jp;

protected JasperReport jr;

protected Map params = new HashMap();

protected DynamicReport dr;

public void buildReport() throws Exception {

DynamicReportBuilder drb = new DynamicReportBuilder();

for (int i = 1; i <= 10; i++) {

AbstractColumn column = ColumnBuilder.getInstance()

.setColumnProperty("Column" + i, String.class.getName())

.setTitle("Column " + i + " Title").setWidth(200).build();

drb.addColumn(column);

}

drb.setUseFullPageWidth(true);

dr = drb.build();

JRDataSource ds = getDataSource();

// Make sure Java Heap Size is set.

// E.g. "-Xms256m -Xmx1024m"

// Virtualizer convert the page and store into a physical files on harddisk.

JRFileVirtualizer virtualizer = new JRFileVirtualizer(100, "C://tmp");

params.put(JRParameter.REPORT_VIRTUALIZER, virtualizer);

System.out.println("Generating...");

jr = DynamicJasperHelper.generateJasperReport(dr, new ClassicLayoutManager(), params);

System.out.println("Filling...");

if (ds != null) {

// JRParameter.IS_IGNORE_PAGINATION default is false,

// if you set to true, virtualizer will not work.

params.put(JRParameter.IS_IGNORE_PAGINATION, new Boolean(false));

jp = JasperFillManager.fillReport(jr, params, ds);

} else {

jp = JasperFillManager.fillReport(jr, params);

}

// If column width more then page width, some column will merge automatically.

// Set the page width to resolve this issue.

//jp.setPageWidth(0);

//jp.setPageHeight(0);

FileOutputStream fileOut = new FileOutputStream("C:/tmp/ExcelReport.xls");

JRExporter exporter = new JExcelApiExporter();

exporter.setParameter(JExcelApiExporterParameter.OUTPUT_STREAM, fileOut);

exporter.setParameter(JExcelApiExporterParameter.JASPER_PRINT, jp);

System.out.println("Exporting...");

exporter.exportReport();

fileOut.flush();

fileOut.close();

}

protected JRDataSource getDataSource() {

// Generate dummy data to show in the report.

List records = new ArrayList();

for (int i = 1; i < 500000; i++) {

Map columns = new HashMap();

for (int j = 1; j <= 10; j++) {

System.out.println("Column" + j);

// The HashMap Key must save with ColumnProperty Name

columns.put("Column" + j, "Record " + i + " Column " + j + " data.");

}

records.add(columns);

}

JRDataSource ds = new JRMapCollectionDataSource(records);

return ds;

}

public static void main(String[] args) throws Exception {

JasperExcelReport jer = new JasperExcelReport();

jer.buildReport();

System.out.println("Done");

}

}