问题
I am testing my method with this form https://help.adobe.com/en_US/Acrobat/9.0/Samples/interactiveform_enabled.pdf
It is being called like so:
Pdf.editForm("./src/main/resources/pdfs/interactiveform_enabled.pdf", "./src/main/resources/pdfs/FILLEDOUT.pdf"));
where Pdf is just a worker class and editForm is a static method.
The editForm method looks like this:
public static int editForm(String inputPath, String outputPath) {
try {
PdfDocument pdf = new PdfDocument(new PdfReader(inputPath), new PdfWriter(outputPath));
PdfAcroForm form = PdfAcroForm.getAcroForm(pdf, true);
Map<String, PdfFormField> m = form.getFormFields();
for (String s : m.keySet()) {
if (s.equals("Name_First")) {
m.get(s).setValue("Tristan");
}
if (s.equals("BACHELORS DEGREE")) {
m.get(s).setValue("Off"); // On or Off
}
if (s.equals("Sex")) {
m.get(s).setValue("FEMALE");
}
System.out.println(s);
}
pdf.close();
logger.info("Completed");
} catch (IOException e) {
logger.error("Unable to fill form " + outputPath + "\n\t" + e);
return 1;
}
return 0;
}
Unfortunately the FILLEDOUT.pdf file is no longer a form after calling this method. Am I doing something wrong?
I was using this resource for guidance. Notice how I am not calling the form.flattenFields(). If I do call that method however, I get an error of java.lang.IllegalArgumentException.
Thank you for your time.
回答1:
Your form is Reader-enabled, i.e. it contains a usage rights digital signature by a key and certificate issued by Adobe to indicate to a regular Adobe Reader that it shall activate a number of additional features when operating on that very PDF.
If you stamp the file as in your original code, the existing PDF objects will get re-arranged and slightly changed. This breaks the usage rights signature, and Adobe Reader, recognizing that, disclaims "The document has been changed since it was created and use of extended features is no longer available."
If you stamp the file in append mode, though, the changes are appended to the PDF as an incremental update. Thus, the signature still correctly signs its original byte range and Adobe Reader does not complain.
To activate append mode, use StampingProperties when you create your PdfDocument:
PdfDocument pdf = new PdfDocument(new PdfReader(inputPath), new PdfWriter(outputPath), new StampingProperties().useAppendMode());
(Tested with iText 7.1.1-SNAPSHOT and Adobe Acrobat Reader DC version 2018.009.20050)
By the way, Adobe Reader does not merely check the signature, it also tries to determine whether the changes in the incremental update don't go beyond the scope of the additional features activated by the usage rights signature.
Otherwise you could simply take a small Reader-enabled PDF and in append mode replace all existing pages by your own content of choice. This of course is not in Adobe's interest...
回答2:
The filled in PDF is still an AcroForm, otherwise the example below would result in the same PDF twice.
public class Main {
public static final String SRC = "src/main/resources/interactiveform_enabled.pdf";
public static final String DEST = "results/filled_form.pdf";
public static final String DEST2 = "results/filled_form_second_time.pdf";
public static void main(String[] args) throws Exception {
File file = new File(DEST);
file.getParentFile().mkdirs();
Main main = new Main();
Map<String, String> data1 = new HashMap<>();
data1.put("Name_First", "Tristan");
data1.put("BACHELORS DEGREE", "Off");
main.fillPdf(SRC, DEST, data1, false);
Map<String, String> data2 = new HashMap<>();
data2.put("Sex", "FEMALE");
main.fillPdf(DEST, DEST2, data2, false);
}
private void fillPdf(String src, String dest, Map<String, String> data, boolean flatten) {
try {
PdfDocument pdf = new PdfDocument(new PdfReader(src), new PdfWriter(dest));
PdfAcroForm form = PdfAcroForm.getAcroForm(pdf, true);
//Delete print field from acroform because it is defined in the contentstream not in the formfields
form.removeField("Print");
Map<String, PdfFormField> m = form.getFormFields();
for (String d : data.keySet()) {
for (String s : m.keySet()) {
if(s.equals(d)){
m.get(s).setValue(data.get(d));
}
}
}
if(flatten){
form.flattenFields();
}
pdf.close();
System.out.println("Completed");
} catch (IOException e) {
System.out.println("Unable to fill form " + dest + "\n\t" + e);
}
}
}
The issue you are facing has to do with the 'reader enabled forms'. What it boils down to is that the PDF file that is initially fed to your program is reader enabled. Hence you can open the PDF in Adobe Reader and fill in the form. This allows Acrobat users to extend the behaviour of Adobe Reader. Once the PDF is filled in and closed using iText it saves the PDF as 'not reader-extended'. This makes it so that the AcroForm can still be filled using iText but when you open the PDF using Adobe Reader the extended functionality you see in the original PDF is gone. But this does not mean the form is flattened.
iText cannot make a form reader enabled, as a matter of fact, the only way to create a reader enabled form is using Acrobat Professional. This is how Acrobat and Adobe Reader interact and it is not something iText can imitate or solve. You can find some more info and a possible solution on this link.
The IllegalArgumentException you get when you call the form.flattenFields() method is because of the way the PDF document was constructed. The "Print form" button should have been defined in the AcroForm, yet it is defined in the contentstream of the PDF, meaning the button in the AcroForm has an empty text value, and this is what causes the exception.
You can fix this by removing the print field from the AcroForm before you flatten.
来源：https://stackoverflow.com/questions/47581765/why-is-my-form-being-flattened-without-calling-the-flattenfields-method