HƯỚNG DẪN DOWNLOAD FILE VỚI P:DOWNLOAD

THƯ VIỆN      
        dependency>
            groupId>javax.portlet/groupId>
            artifactId>portlet-api/artifactId>
            version>2.0/version>
            scope>provided/scope>
        /dependency>
        dependency>
            groupId>com.liferay.portal/groupId>
            artifactId>portal-service/artifactId>
            version>${liferay.version}/version>
            scope>provided/scope>
        /dependency>
        dependency>
            groupId>com.liferay.portal/groupId>
            artifactId>portal-impl/artifactId>
            version>${liferay.version}/version>
            scope>provided/scope>
        /dependency>
       
TRONG BEAN

public void exportToExcel() {

        CellsDataTableMapThongKeHangMucTheoNam cellsDataTableMapThongKeHangMucTheoNam_Moi = new CellsDataTableMapThongKeHangMucTheoNam(hangMucMois, 0);
        CellsDataTableMapThongKeHangMucTheoNam cellsDataTableMapThongKeHangMucTheoNam_ChuyenTiep = new CellsDataTableMapThongKeHangMucTheoNam(hangMucChuyenTieps, hangMucMois.size());
        WorkbookDesigner designer = new WorkbookDesigner();
        try {

            String templatePath = FacesContext.getCurrentInstance()
                    .getExternalContext().getRealPath("/") + File.separator + "TemplateExports" + File.separator + "thongketheonam_in.xlsx";

            Workbook workbook = new Workbook(templatePath);

            designer.setWorkbook(workbook);
            designer.setDataSource("title", "BÁO CÁO HẠNG MỤC SỬ DỤNG NGÂN SÁCH SỰ NGHIỆP THEO NĂM " + namSearch);
            designer.setDataSource("namGiaiNgan", "Giải Ngân Năm " + namSearch);
            designer.setDataSource("hangmucmoi", cellsDataTableMapThongKeHangMucTheoNam_Moi);
            designer.setDataSource("tongHangMucMoi", hangMucMois.size());
            designer.setDataSource("tongHangMucChuyenTiep", hangMucChuyenTieps.size());
            designer.setDataSource("tongHangMuc", hangMucMois.size() + hangMucChuyenTieps.size());
            designer.setDataSource("tongMucDauTuHangMucMoi", tongTongMucDauTuHMMoi);
            designer.setDataSource("tongMucDauTuHangMucChuyenTiep", tongTongMucDauTuHMChuyenTiep);
            designer.setDataSource("tongMucDauTuHangMuc", tongTongMucDauTuHMMoi + tongTongMucDauTuHMChuyenTiep);
            designer.setDataSource("hangmucchuyentiep", cellsDataTableMapThongKeHangMucTheoNam_ChuyenTiep);

            designer.process(false);

            ByteArrayOutputStream ous = new ByteArrayOutputStream();

            designer.getWorkbook().save(ous, SaveFormat.XLSX);


            PortletResponse portletResponse = context.getPortletResponse();
            HttpServletResponse res = PortalUtil.getHttpServletResponse(portletResponse);
            res.setHeader("Content-Disposition", "attachment; filename=\"" + "thongkedanhmuchangmuc.xlsx"  + "\"");
            res.setHeader("Content-Transfer-Encoding", "binary");
            res.setContentType("Content-type: application/vnd.ms-excel");
            res.flushBuffer();


            OutputStream out = res.getOutputStream();
            byte[] buffer = new byte[4096];
            int byteread;
            InputStream is = new ByteArrayInputStream(ous.toByteArray());
            while ((byteread = is.read(buffer)) != -1) {
                out.write(buffer, 0, byteread);
                buffer = new byte[4096];
            }
            out.flush();
            is.close();

        } catch (Exception e) {

            e.printStackTrace();
        }
    }

TRÊN VIEW

p:commandButton value="#{msgs['btn.indanhsach']}" rendered="#{thongKeDuAnBean.showInDanhSach}"  ajax="false" icon="ui-icon-arrowthick-1-s">
            p:fileDownload value="#{thongKeDuAnBean.exportToExcel()}" /
/p:commandButton