Browsers freeze by file download

Question

I got a problem when files were download , I can't get any actions or events when clicking any links , butttons and menues after download process was done.

Below is my codes for excel file download button ...

    Button btnDownloadExcel = new Button("Excel Download");
    btnDownloadExcel.addStyleName("downloadButton");
    btnDownloadExcel.addClickListener(new ClickListener() {

        @Override
        public void buttonClick(final ClickEvent event) {
            StringBuilder url = new StringBuilder("/myproject/filedownload.html?category=excel");
            url.append("&seq=" + 111);
            getUI().getPage().open(url.toString(), "_self");
        }
    });

Below is servlet for handle excel file download request (I used JExcel API for excel file)

@WebServlet(value = "/filedownload.html")
public class DownloadServletController extends HttpServlet {
private final Logger log = LoggerFactory.getLogger(DownloadServletController.class);

protected final void doGet(final HttpServletRequest request,
        final HttpServletResponse response) throws ServletException, IOException {
    String category = request.getParameter("category");
    long seq = request.getParameter("seq") == null ? -1L : Long.parseLong(request.getParameter("seq"));
    byte[] stream = null;
    if (category.equals("excel")) {
        try {
            stream = getSampleExcelStream(seq);
        }
        catch (BusinessException e) {
            log.error("Generating streams for " + category + " got Error !" + e);
        }
        ExcelSupport.createExcel("Test", seq, stream, response);
    }
}

private byte[] getSampleExcelStream(final long seq) throws BusinessException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try {
        String staticDir = System.getProperty("staticDir");
        String templateDir = staticDir + "/templates/sample_excel_template.xls";

        WorkbookSettings wsWrite = new WorkbookSettings();
        wsWrite.setEncoding("UTF-8");
        wsWrite.setAutoFilterDisabled(false);
        WritableWorkbook workBook = Workbook.createWorkbook(baos, Workbook.getWorkbook(new File(templateDir)),
                wsWrite);

        workBook.write();
        baos.close();
        workBook.close();
    }
    catch (BiffException e) {
        throw new BusinessException("Excel file Creating Error!");
    }
    catch (WriteException e) {
        throw new BusinessException("Error ! writing excel file process has occured!");
    }
    catch (FileNotFoundException e) {
        throw new BusinessException("FileNotFoundException, when getting stream for excel", e);
    }
    catch (IOException e) {
        throw new BusinessException("IOException, when getting stream for excel", e);
    }
    return baos.toByteArray();
}
}

ExcelSupport.java is below

public final class ExcelSupport {
private ExcelSupport() {
}

private static final Logger LOGGER = LoggerFactory.getLogger(ExcelSupport.class);

public static void createExcel(final String fileNamePrefix, final long seq,
        final byte[] stream, final HttpServletResponse response) {
    StringBuffer fileName = new StringBuffer();
    fileName.append(fileNamePrefix + "_");
    if (seq > -1) {
        fileName.append("(uid-" + seq + ")_");
    }
    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
    fileName.append(sdf.format(new Date()));
    fileName.append(".xls");

    StringBuffer sbContentDispValue = new StringBuffer();
    sbContentDispValue.append("inline");
    sbContentDispValue.append("; filename=");
    sbContentDispValue.append(fileName);

    response.setContentType("application/msexcel");
    response.addHeader("Cache-Control", "max-age=30");
    response.addHeader("Content-disposition", sbContentDispValue.toString());
    response.setContentLength(stream.length);
    try {
        ServletOutputStream osStream = response.getOutputStream();
        osStream.write(stream);
        osStream.flush();
        osStream.close();
    }
    catch (IOException e) {
        LOGGER.error("Creating Excel for " + fileName + " got Error !" + e);
    }
}
}

Can somebody correct me what I am wrong ? Download process was fine , nothing error and I got excel file successfully. But I have no idea why browser was freeze. I can't see any error logs or messages in IDE console and browser's console. Thanks for reading my question !

PS : I am sure this codes work fine and did not freeze on other GWT projects.

Answer 1

Now I found the problem . I used Network console of Firefox 31 and here is screen-shoot for before download and here is after download. I notice that I lost all web datas because the replacing url by getUI().getPage().open(url.toString(), "_self");

So , if I use others instead of _self , everythings were fine but browsers were block popups. I can't tell the users to enable popups of their browsers . So , finally I use Link component as below ..

    Link linkDownloadExcel = new Link("Excel Download", new ExternalResource(
        "/myproject/filedownload.html?category=excel&seq=" + 111), "_blank", -1, -1, BorderStyle.DEFAULT);
    linkDownloadExcel.addStyleName("downloadButton");
    linkDownloadExcel.setIcon(new ExternalResource("/myproject/images/excel-icon.png"));
    hlButtonLayout.addComponent(linkDownloadExcel);