Merging 1000 PDF thru iText throws java.lang.OutOfMemoryError: Java heap space

Question

I am trying to merge 1000 PDF Files thru iText. I am not sure where the memory leakage is happening. Below is the sample code. Note that i am removing the child-pdf file as soon as i merge to the parent file. Please pointout bug in below code or is there any better way to do this with out memory conception. This process is done thru servlet (not standalone program)

FileInputStream local_fis = null;
BufferedInputStream local_bis = null;
File localFileObj = null;
for(int taIdx=0;taIdx<totalSize;taIdx++){
    frObj = (Form3AReportObject)reportRows.get(taIdx);
    localfilename = companyId + "_" +  frObj.empNumber + ".pdf";

    local_fis = new FileInputStream(localfilename);
    local_bis = new BufferedInputStream(local_fis); 
    pdfReader = new PdfReader(local_bis);

    cb = pdfWriter.getDirectContent(); 
    document.newPage();
    page = pdfWriter.getImportedPage(pdfReader, 1);
    cb.addTemplate(page, 0, 0);
    local_bis.close();
    local_fis.close();

    localFileObj = new File(localfilename);
    localFileObj.delete();
}
document.close();

Answer 1

Have you tried increasing max heap size from the default (which is only 64mb)?

See:

• How to deal with “java.lang.OutOfMemoryError: Java heap space” error (64MB heap size)
• Java How To ...: 6 Common Errors in Setting Java Heap Size

Answer 2

Who says there is a memory leak? Your merged document needs to fit into memory in its entirety, there's no way around it, and it may well be larger than the default heap size of 64MB in memory (rather than on disc).

I don't see a problem with your code, but if you want to diagnose it in detail, use visualvm's heap profiler (comes with the JDK since Java 6 update 10 or so).

Answer 3

You might want to try something like the following (exception handling, file close and delete removed for clarity):

for(int taIdx = 0; taIdx < totalSize; taIdx++) {
    Form3AReportObject frObj = (Form3AReportObject)reportRows.get(taIdx);

    localfilename = companyId + "_" +  frObj.empNumber + ".pdf";

    FileInputStream local_fis = new FileInputStream(localfilename);

    pdfWriter.freeReader(new PdfReader(local_fis));

    pdfWriter.flush();
}

pdfWriter.close();