Merging two pdf documents with PDFMergerUtility throws: IOException("Page tree root must be a dictionary")

Question

I have a spring boot application and I am trying to merge two pdf files. The one I am getting as a byte array from another service and the one I have it locally in my resources file: /static/documents/my-file.pdf. This is the code of how I am getting byte array from my file from resources:

public static byte[] getMyPdfContentForLocale(final Locale locale) {
    byte[] result = new byte[0];
    try {
        final File myFile = new ClassPathResource(TEMPLATES.get(locale)).getFile();
        final Path filePath = Paths.get(myFile.getPath());
        result = Files.readAllBytes(filePath);
    } catch (IOException e) {
        LOGGER.error(format("Failed to get document for local %s", locale), e);
    }
    return result;
}

I am getting the file and getting the byte array. Later I am trying to merge this two files with the following code:

PDFMergerUtility pdfMergerUtility = new PDFMergerUtility();
pdfMergerUtility.addSource(new ByteArrayInputStream(offerDocument));
pdfMergerUtility.addSource(new ByteArrayInputStream(merkblattDocument));
ByteArrayOutputStream os = new ByteArrayOutputStream();
pdfMergerUtility.setDestinationStream(os);
pdfMergerUtility.mergeDocuments(null);
os.toByteArray();

But unfortunately it throws an error:

throw new IOException("Page tree root must be a dictionary");

I have checked and it makes this validation before it throws it:

if (!(root.getDictionaryObject(COSName.PAGES) instanceof COSDictionary))
    {
        throw new IOException("Page tree root must be a dictionary");
    }

And I really have no idea what does this mean and how to fix it. The strangest thing is that I have created totally new project and tried the same code to merge two documents (the same documents) and it works!

Additionally what I have tried is:

Change the spring boot version if it is ok
Set the mergeDocuments method like this: pdfMergerUtility.mergeDocuments(setupMainMemoryOnly())
Set the mergeDocuments method like this: pdfMergerUtility.mergeDocuments(setupTempFileOnly())
Get the bytes with a different method not using the Files from java.nio:
And also executed this in a different thread
Merging files only locally stored (in resources)
Merging the file that I am getting from another service - this works btw and that is why I am sure he is ok

Can anyone help with this?

Please make sure you're using the latest PDFBox version (2.0.19) and share your file. Also make sure that resource filtering is disabled (this is a common pitfall!). https://stackoverflow.com/questions/55722595/ — Tilman Hausherr, Mar 20 '20 at 14:03
Why would the resource filtering be causing issues? I am actually using that to put data in some other xml files that I have. — f.trajkovski, Mar 20 '20 at 14:24
Ok you are totally right about this filtering. But unfortunately I can't disable it. Is there any other way to avoid this in my java code? — f.trajkovski, Mar 20 '20 at 14:42
That is mentioned in the links from my first comment, e.g. here: https://stackoverflow.com/a/24282250/535646 — Tilman Hausherr, Mar 20 '20 at 18:39

f.trajkovski · Accepted Answer · 2020-03-21T17:43:55.990

0

The issue as Tilman Hausherr said is in that resource filtering that you can find in your pom file. If you have a case where you are not allowed to modify this then this approach will help you:

final String path = new 
ClassPathResource(TEMPLATES.get(locale)).getFile().getAbsolutePath();
final File file = new File(path);
final Path filePath = Paths.get(file.getPath());
result = Files.readAllBytes(filePath);

and then just pass the bytes to the pdfMergerUtility object (or even the whole file instead of the list of bytes).

edited Mar 21 '20 at 17:43

answered Mar 20 '20 at 16:14

f.trajkovski

794
9
24

Don't know if this approach will work in production when it is a jar outside of your IDE. – Tilman Hausherr Mar 20 '20 at 17:13
1

You were right @TilmanHausherr. You shouldn't use file for location. – f.trajkovski Jun 23 '20 at 22:30

Merging two pdf documents with PDFMergerUtility throws: IOException("Page tree root must be a dictionary")

1 Answers1