Need a way to instantiate ZipOutputStream object in the service layer

Question

I have the following block of code in my bean class -

HttpServletResponse response = (HttpServletResponse) getFacesContext().getExternalContext().getResponse();
ZipOutputStream zos = new ZipOutputStream(response.getOutputStream());

From my bean I call my service layer, which in turn calls the database layer, retrieves data and writes the files generated in a ZIP file in the service layer. I have an issue where I do not have a clue what to do if there are no files generated.

When I instantiate ZipOutputStream object in my bean, it creates a ZIP file and opens up a "Opening Extracts.zip" window, and when I click on OK, I get an error because there are no files in the ZIP folder.

Can somoone please tell me if there is any way I can move the zos instantiation to the service layer without having to pass the response object?

Thanks, Raaz

Answer 1

I found I can do the following to fix my issue -

In my bean class, I wrote the following code -

HttpServletResponse response = (HttpServletResponse) getFacesContext().getExternalContext().getResponse();
ByteArrayOutputStream outputStream = null;

try {
    outputStream = //Call service to generate the extract, return outputStream ; 
    if(outputStream != null){
    response.setContentType(T3Constants.MIME_ZIP);
    response.setHeader(T3Constants.CONTENT_DISPOSITION, ATTACH_FILE_NAME);
    response.getOutputStream().write(outputStream.toByteArray());
    response.flushBuffer();
    FacesContext.getCurrentInstance().responseComplete();
    outputStream.close();
    } else {
    formatFacesMessage(FacesMessage.SEVERITY_WARN, "No data for selected filter", "No data for selected filter");
    }
}

In my service, I wrote the following code -

ByteArrayOutputStream outputStream = null;
if(CollectionUtils.isNotEmpty(list returned from DB)) {
    outputStream = new ByteArrayOutputStream();
    ZipOutputStream zos = new ZipOutputStream(outputStream);
    //Add files to ZIP
    outputStream = new ByteArrayOutputStream();
    workbook.write(outputStream);
    zos.putNextEntry(new ZipEntry(xlsName.toString()));
    zos.write(outputStream.toByteArray());
    zos.flush();
    zos.close();
return outputStream;
}

Thanks, Raaz