在itext7中将html转换为pdf时出错

Question

To convert my html to pdf i use itext7's API convertToDocument, passing parameters the template's ByteArrayInputStream, the PDFDocument and convertProperties.

relevant code snippet:

HtmlConverter.convertToDocument(new ByteArrayInputStream(templateWritten), pdfDocument, converterProps);

As docs says, if I set baseURI of convertProperties there is no problem, but if I set PDF fonts this error shows up when the are many concurrent calls:

"Pdf indirect object belongs to other PDF document. Copy object to current pdf document.”

creation of convert properties

private ConverterProperties addResourcesForInitiative(String templateKey, FontProvider fontProvider) {
//        CustomDefaultFontProvider cdfp = new CustomDefaultFontProvider();
        ConverterProperties converterprops = new ConverterProperties();
//        converterprops.setFontProvider(fontProvider);
        converterprops.setBaseUri(ConfigurationManager.getParamValue("resource.path") + templateKey + "/resources/");
        log.info("Properties for conversione are setted. Url of folder loaded " + converterprops.getBaseUri());
        return converterprops;
    }

the object is created each call before convertToDocument API

am I missing something?

thanks all for your help

Answer 1

I experienced the same problem. It is related to (but not a duplicate of) Itext7 generate pdf with Exception "Pdf indirect object belongs to other PDF document. Copy object to current pdf document."

What I didn't understand about iText 7 at first, is that you have a FontProgram and a PdfFont .

• FontProgram is a class that contains all the information that iText needs to use a font program. It can be reused in a process that creates many different PDF files.
• PdfFont is a class that uses FontProgram in the context of a single document. Each PdfFont object belongs to exactly one PdfDocument .

If you try to use a PdfFont object to create another document, you get the error "Pdf indirect object belongs to other PDF document. Copy object to current pdf document."

In other words: you can't just reuse PdfFont objects, only FontProgram objects. This can be a problem when reusing ConverterProperties (or a FontProvider ). The trick is not to cache PdfFont objects in a FontProvider , but cache the FontProgram instead.

As this is very confusing, I have asked the iText 7 development team to fix this. When I look at the closed ticketing system, I can see that the documentation will be fixed, and that efforts will be done with respect to the ConverterProperties . This means that you'll see improvements in the next version.

In the meantime, I have fixed this for myself by changing the way I use a FontProvider and ConverterProperties . New instances of PdfFont have to be created for every new document, and I understand why: PdfFont keeps track of the characters that are used in a specific document, and uses that information to create a font subset. That subset is different for every document; hence every document needs a different PdfFont instance.

I will add a reference to this question in the tickets about this topic.