[PDFBOX-3521] FontProvider not thread safe

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.0.3, 3.0.0 PDFBox
• Fix Version/s: 2.0.4, 3.0.0 PDFBox
• Component/s: PDModel
• Labels: concurrency
• Assignee: Tilman Hausherr
• Reporter: rob hinds
• Created: 03/Oct/16 13:33
• Updated: 25/Mar/17 18:13
• Resolved: 08/Oct/16 18:51

Description

I understand that PDFBox is not yet thread-safe, however, from reading this comment on a similar ticket, it seems like the fonts should be thread safe and is something that we want to fix. However, I am experiencing an intermittent NullPointerException when running multi-threaded unit tests that attempt to read several PDFs at once (see details here.

Inside FontMapperImpl.java the getProvider and setProvider methods are synchronised:

    public synchronized void setProvider(FontProvider fontProvider)
    {
        this.fontProvider = fontProvider;
        fontInfoByName = createFontInfoByName(fontProvider.getFontInfo());
    }

    /**
     * Returns the font service provider. Defaults to using FileSystemFontProvider.
     */
    public synchronized FontProvider getProvider()
    {
        if (fontProvider == null)
        {
            setProvider(DefaultFontProvider.INSTANCE);
        }
        return fontProvider;
    }

However, the calling code from the findFont() method is not synchronised:

        // make sure the font provider is initialized
        if (fontProvider == null)
        {
            getProvider();
        }

        // first try to match the PostScript name
        FontInfo info = getFont(format, postScriptName);
        if (info != null)
        {
            return info.getFont();
        }

As a result, if multiple threads attempt to access this at once, thread A may be in the setProvider method and have set fontProvider, but still processing the creation of fontInfoByName - so thread B could attempt to access before initialised.