문제 설명
iText로 가변 페이지 PDF를 생성하려고 할 때 예외 (Exception when attempting to generate variable‑page PDF with iText)
I'm trying to create an auto‑filled PDF of a government payroll form, which involves the possibility of a variable number of pages. I'm currently storing each page as a Map, with the keys being the names of the fields and the values being their contents. At the moment, I have this code:
in = new FileInputStream(inputPDF);
PdfCopyFields adder = new PdfCopyFields(outStream);
PdfReader reader = null;
PdfStamper stamper = null;
ByteArrayOutputStream baos = null;
for (int pageNum = 0; pageNum < numPages; pageNum++) {
reader = new PdfReader(in);
baos = new ByteArrayOutputStream();
stamper = new PdfStamper(reader, baos);
AcroFields form = stamper.getAcroFields();
Map<String, String> page = pages.get(pageNum);
setFieldsToPage(form, pageNum);
populatePage(form, page, pageNum);
stamper.close();
reader = new PdfReader(baos.toByteArray());
adder.addDocument(reader);
}
The methods called are:
private void populatePage(AcroFields form, Map<String, String> pageMap, int pageNum) throws Exception {
ArrayList<String> fieldNames = new ArrayList<String>();
for (String key : pageMap.keySet()) {
fieldNames.add(key);
}
for (String key : fieldNames) {
form.setField(key + pageNum, pageMap.get(key));
}
}
and
private void setFieldsToPage(AcroFields form, int pageNum) {
ArrayList<String> fieldNames = new ArrayList<String>();
Map<String, AcroFields.Item> fields = form.getFields();
for (String fieldName : fields.keySet()) {
fieldNames.add(fieldName);
}
for (String fieldName : fieldNames) {
form.renameField(fieldName, fieldName + pageNum);
}
}
The issue is that this throws an exception on the second iteration through the loop: at reader = new PdfReader(in); I get the following exception: java.io.IOException: PDF header signature not found. What am I doing wrong here, and how do I fix it?
EDIT: Here is the exception:
java.io.IOException: PDF header signature not found.
at com.lowagie.text.pdf.PRTokeniser.checkPdfHeader(Unknown Source)
at com.lowagie.text.pdf.PdfReader.readPdf(Unknown Source)
at com.lowagie.text.pdf.PdfReader.<init>(Unknown Source)
at com.lowagie.text.pdf.PdfReader.<init>(Unknown Source)
By the way, I'm sorry if the formatting is bad ‑ this is my first time using stackoverflow.
참조 솔루션
방법 1:
Your issue is that you essentially try to read the same input stream multiple times while it is positioned at its end already after the first time:
in = new FileInputStream(inputPDF);
[...]
for (int pageNum = 0; pageNum < numPages; pageNum++) {
reader = new PdfReader(in);
[...]
}
The whole stream is read in the first iteration; thus, in the second one new PdfReader(in) essentially tries to parse an empty file resulting in your
java.io.IOException: PDF header signature not found
You can fix that by simply constructing the PdfReader with the input file path directly every time:
for (int pageNum = 0; pageNum < numPages; pageNum++) {
reader = new PdfReader(inputPDF);
[...]
}
Two more things, though:
You don't close your
PdfReaderinstances after use. In the most recent iText versions implicit closing of readers has been taken out of the code as it collides with numerous use cases. Thus, after you finished working with a reader (this includes that any stamper etc using that reader also is closed), you should close the reader explicitly.In general, if you have a PDF already in your file system, opening a PdfReader for it via a
FileInputStreamis very wasteful resource‑wise ‑‑‑ a reader initialized with an input stream first completely reads that stream into memory (byte[]) and then parses the in‑memory representation; a reader initialized with a file path directly parses on‑disc representation.
방법 2:
The exception tells you that the file you're reading doesn't start with %PDF‑.
Write a small example that doesn't involve iText and check the first 5 bytes of the InputStream in and you'll find out what you're doing wrong (we can't tell you unless you show us those 5 bytes).
(by dais314、mkl、Bruno Lowagie)