使用Java中的pdfbox为PDF中的方程插入双值

Question

I'm struggling with a little Java Project: I made a Program which autofills a PDF Formular. Mostly everything works fine for me, but there is a Problem: In this PDF Formular (which is given from my company, so I have to deal with this document) is a equation Field, which is used for calculation the Costs from Number of Items and the single Price. When I insert the Price of a single Item as a String to my PDF

    public void setEinzelpreis(String Einzelpreis)
{
    try {
        fieldList.get(30).setValue(Einzelpreis);
...

There should be the single Price on the empty field in the first row. The last Cell of the row is auto-calculated by the pdf. When I Click in the PDF in the "empty" Field, the Value appears: When I click to another Field, the Value disappears. This is my Problem. I'm getting the FieldList via pdfbox and the Code for getting my fieldList of the PFD is:

try {
    pdfTemplate = PDDocument.load(template);
    PDDocumentCatalog docCatalog = pdfTemplate.getDocumentCatalog();
    PDAcroForm acroForm = docCatalog.getAcroForm();
    if (acroForm != null)
    {
    // Get field names
    fieldList = acroForm.getFields();
    
    }
...

So, can anybody tell what I'm doing wrong? Maybe the PDF wants a double Value for the equation and I am giving a String? But I don't know how to write a double in the FieldList. Thanks a lot for every hint!

Edit:
The PDF File which I'm using: https://1drv.ms/b/s!Av6exjPNXlgOioouAuXL6QV4eUGkqg?e=ocfhvC

And this is the file I generated: https://1drv.ms/b/s!Av6exjPNXlgOioovK-HuRuXW2aRy_w?e=D1ZCA8

The strange thing is: when I change the value in the document by hand, everything acts normal, even with a different Document Viewer.

Answer 1

First of all, the AcroForm form structure in your PDF is weird. It looks like someone used a graphical form generation tool he did not understand and clicked, dragged, dropped, copied, ... until the form in a viewer did what he wanted, not caring about it having become difficult to maintain.

In particular the Einzelpreis fields have a completely unnecessary structure of intermediate and final fields, eg

Thus, the field Einzelpreis in € exkl USt1 (the '€' is missing in the tree above) is not the one to fill in, it's merely an intermediary field. The actual form field to fill in is Einzelpreis in € exkl USt1.0.0.0.0 .

Unfortunately you in your code simply grab the 30th field in the field list returned by PDAcroForm , and this field happens to be the intermediary field Einzelpreis in € exkl USt1 ; as an intermediary field it has no visible widgets of its own, so your setValue call doesn't change the visible Einzelpreis.

The JavaScript instruction calculating the Gesamtpreis uses the value from the final field, too:

AFSimple_Calculate("PRD", new Array ("Anzahl1", "Einzelpreis in € exkl USt1.0.0.0.0"));

But as the field value is inheritable and none of the .0 fields has an own value, the calculation sees the 100 once form calculation has been triggered and uses it.

Thus, you should fill the Einzelpreis in € exkl USt1.0.0.0.0 field instead. And the more secure way to retrieve it is not by index in a field list but by name:

PDField fieldByName = acroForm.getField("Einzelpreis in € exkl USt1.0.0.0.0");

(excerpt from FillInForm test testFill2020_04BeschaffungsantragEinzelpreis )

After filling that field, the "100" should be visible in your form.

The remaining problem that the Gesamtpreis value is not calculated is due to the fact already mentioned by @Tilman in a comment to the question: PDFBox doesn't use javascript . Thus, you have to calculate those values yourself and update the fields in question accordingly.

If you need to know the correct name of a form field, you can do as Tilman proposed and use the PDFBox PDFDebugger. If you hover over the field there, it will display the name in the status bar at the bottom.

By the way, the AcroForm method getFields won't return the field required here anyways. As documented in its JavaDocs, this method will return all of the documents root fields , no fields further down in the hierarchy, at least not immediately. (From the user perspective the method name getFields is a misnomer. It is accurate, though, from the PDF specification perspective as the corresponding entry in the AcroForms object has the key Fields .)

Beware, though, you probably will have to update your PDFBox version. In earlier versions PDFBox did not update appearances of fields with JavaScript actions (believing some JavaScript would fill it in anyways). I used the current 3.0.0-SNAPSHOT in which that behavior has been changed.