How to create zip file with two outputStreams (working with JSF)

Question

I've got two outputstreams (filled with data by jasper reports to generate one excel and one csv). The filling of the outputstreams works just fine, but now I have to pack both "streams / files" in to a zip to be downloaded. How could I do this?

The code to download just one file is the following:

public void exportInternalEvaluation() {
    exportStats(ExportingValues.STATISTICS_INTERNAL_EVALUTATION, EXCEL_NAME, solvedDossiers,
            "application/vnd.ms-excel");
}

private void exportStats(ExportingValues exportingValues, String fileName, Collection < ? > collection,
        String contentType) {
    OutputStream os = null;
    try {
        FacesContext fc = FacesContext.getCurrentInstance();
        ExternalContext ec = fc.getExternalContext();

        ec.responseReset();
        ec.setResponseContentType(contentType);
        ec.setResponseHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
        os = ec.getResponseOutputStream();

        statsLocal.generateStatStream(collection, os, exportingValues.getJasperFileName(null),
                exportingValues.getReportingType());

        fc.responseComplete();
    } 
}

This code is setting the content type to excel and lets me download the file. I've already found the following:

        ZipOutputStream zos = new ZipOutputStream(os);  //create a zipOutputStream with my responseOutputStream

but then I'm stuck on creating the ZipEntries. How can I create 2 entries (1 excel and 1 csv) from 2 different streams?

EDIT: And I don't really want to create 2 tempfiles and add them to the zip. I'd like to find a way to "add" the 2 outputstreams to a zip file creating 2 different files without having to create them first (even tempFiles..). If possible though...

Answer 1

You can decorate the response stream with a ZipOutputStream and have your generator code write to that ensuring that you create new entries between each call:

try (OutputStream os = ec.getResponseOutputStream();
    ZipOutputStream zout = new ZipOutputStream(os)) {
  zout.putNextEntry(new ZipEntry("foo.xls"));
  generate(zout, "Excell gen call args");
  zout.closeEntry();
  zout.putNextEntry(new ZipEntry("foo.csv"));
  generate(zout, "CSV gen call args");
  zout.closeEntry();
}