iText - OutOfMemory creating more than 1000 PDFs

Question

I want to create a ZipOutputStream filled with PDF-As. I'm using iText (Version 5.5.7). For more than 1000 pdf entries I get an OutOfMemory-exception on doc.close() and can't find the leak.

ByteArrayOutputStream baos = new ByteArrayOutputStream();
ZipOutputStream zos = new ZipOutputStream(new BufferedOutputStream(baos));
zos.setEncoding("Cp850");
for (MyObject o : objects) {
try {
    String pdfFilename = o.getName() + ".pdf";
    zos.putNextEntry(new ZipEntry(pdfFilename));
    pdfBuilder.buildPdfADocument(zos);
    zos.closeEntry();
} ...

PdfBuilder

public void buildPdfADocument(org.apache.tools.zip.ZipOutputStream zos){
   Document doc = new Document(PageSize.A4);
   PdfAWriter writer = PdfAWriter.getInstance(doc, zos, PdfAConformanceLevel.PDF_A_1B);
   writer.setCloseStream(false); // to not close my zos
   writer.setViewerPreferences(PdfWriter.ALLOW_PRINTING | PdfWriter.PageLayoutSinglePage);
   writer.createXmpMetadata();
   doc.open();
   // adding Element's to doc
   // with flushContent() on PdfPTables
   InputStream sRGBprofile = servletContext.getResourceAsStream("/WEB-INF/conf/AdobeRGB1998.icc");
   ICC_Profile icc = ICC_Profile.getInstance(sRGBprofile);
   writer.setOutputIntents("Custom", "", "http://www.color.org", "sRGB IEC61966-2.1", icc);
   //try to close/flush everything possible
   doc.close();
   writer.setXmpMetadata(null);
   writer.flush();
   writer.close();
   if(sRGBprofile != null){
     sRGBprofile.close();
   }
}

Any suggestions how can I fix it? Am I forgetting something? I've already tried to use java ZipOutputStream but it makes any difference.

---

Thx for ur answers! I understand the issue with the ByteOutputStream, but I am not sure what's the best approach in my case. It's a web application and I need to pack the zip in a database blob somehow.

What I am doing now is creating the PDFs directly into the ZipOutputStream with iText and saving byte array of the corresponding ByteArrayOutputSteam to blob. Options that I see are:

Split my data in 500 object packages, save first 500 PDFs to the database and then open the zip and add the next 500 ones and so on... But I assume that this creates me the same situation as I have now, namely too big stream opened in the memory.

Try to save the PDFs on the server (not sure if there's enough space), create temporary zip file and then submit the bytes to the blob...

Any suggestions/ideas?

Answer 1

It's because your ZipOutputStream is backed by a ByteArrayOutputStream, so even closing the entries keeps the full ZIP contents in memory.