Create zip on the fly with csv files inside

Question

I am trying to create a zip file on the fly containing a bunch of csv files to return from a servlet, and this is very confusing. A little guide would be great. Here are the pieces of code that I have, something needs to work together:

// output stream coming from httpResponse, thats all fine ZipOutputStream zip = new ZipOutputStream(outputStream); // using the openCSV library to create the csv file CSVWriter writer = new CSVWriter(Writer?); // what writer do I use? I want to write to memory, not a file writer.writeNext(entries); writer.close(); // at this point should I have the csv file in memory somewhere? //and then try to copy it into the zip file? int length; byte[] buffer = new byte[1024 * 32]; zip.putNextEntry(new ZipEntry(getClass() + ".csv")); // the 'in' doesn't exist yet - where am I getting the input stream from? while((length = in.read(buffer)) != -1) zip.write(buffer, 0, length); zip.closeEntry(); zip.flush(); 

Answer 1

You can transfer a ZIP file containing your CSV as follows:

 try { OutputStream servletOutputStream = httpServletResponse.getOutputStream(); // retrieve OutputStream from HttpServletResponse ZipOutputStream zos = new ZipOutputStream(servletOutputStream); // create a ZipOutputStream from servletOutputStream List<String[]> csvFileContents = getContentToZIP(); // get the list of csv contents. I am assuming the CSV content is generated programmatically int count = 0; for (String[] entries : csvFileContents) { String filename = "file-" + ++count + ".csv"; ZipEntry entry = new ZipEntry(filename); // create a zip entry and add it to ZipOutputStream zos.putNextEntry(entry); CSVWriter writer = new CSVWriter(new OutputStreamWriter(zos)); // There is no need for staging the CSV on filesystem or reading bytes into memory. Directly write bytes to the output stream. writer.writeNext(entries); // write the contents writer.flush(); // flush the writer. Very important! zos.closeEntry(); // close the entry. Note : we are not closing the zos just yet as we need to add more files to our ZIP } zos.close(); // finally closing the ZipOutputStream to mark completion of ZIP file } catch (Exception e) { log.error(e); // handle error }