Getting NestedNullException

[lepiyao]

Hi,
I'm always getting this exception 

'javax.servlet.ServletException: java.lang.NoClassDefFoundError: org/apache/commons/beanutils/NestedNullException'

and the root cause

'java.lang.ClassNotFoundException: org.apache.commons.beanutils.NestedNullException'

, everytime i run my function on my backing bean.
And on the Console Log on my eclipse, it shown that 'JRBeanCollectionDataSource' that cause this exception.

I'm using a simple commandButton (with ajax="false") in my.xhtml file to trigger the function on my backing bean.
Any solution for this ?

 

public void printPDF() throws JRException, IOException {                List<PersonTest> dataSource = new ArrayList<>();        dataSource.add(new PersonTest("Tester","One"));        dataSource.add(new PersonTest("Asdsa","Two"));        dataSource.add(new PersonTest("Wasdsaw","Three"));        String filename = "names.pdf";                String jasperPath ="/resources/report/report.jasper";        this.pdf(null, jasperPath, dataSource, filename);            }        public void pdf(Map<String, Object> params, String jasperPath, List<?> dataSource, String fileName) throws JRException, IOException {        String relativeWebPath = FacesContext.getCurrentInstance().getExternalContext().getRealPath(jasperPath);        File file = new File(relativeWebPath);        JRBeanCollectionDataSource source = new JRBeanCollectionDataSource(dataSource, false);        JasperPrint print = JasperFillManager.fillReport(file.getPath(), params, source);                HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance().getExternalContext().getResponse();        response.addHeader("Content-disposition", "attatchment;filename=" + fileName);             ServletOutputStream stream = response.getOutputStream();        JasperExportManager.exportReportToPdfStream(print, stream);        FacesContext.getCurrentInstance().responseComplete();    }[/code]