[TIKA-2896] NullPointerException in MimeTypesReader.releaseParser()

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.21
• Fix Version/s: 1.22
• Component/s: mime
• Assignee: Unassigned
• Reporter: Eamonn Saunders
• Created: 17/Jun/19 16:54
• Updated: 18/Jun/19 08:55
• Resolved: 18/Jun/19 08:55

Description

We have encountered a situation where the call to parser.reset() in the following code snippet results in a NullPointerException.

    private static void releaseParser(SAXParser parser) {
        try {
            parser.reset();
        } catch (UnsupportedOperationException e) {
            //ignore
        }

releaseParser() is called in the finally block of MimeTypesReader.read()

    public void read(InputStream stream) throws IOException, MimeTypeException {
        SAXParser parser = null;
        try {

            parser = acquireSAXParser();
            parser.parse(stream, this);
        } catch (TikaException e) {
            throw new MimeTypeException("Unable to create an XML parser", e);
        } catch (SAXException e) {
            throw new MimeTypeException("Invalid type configuration", e);
        } finally {
            releaseParser(parser);
        }
    }

The parser variable will be null coming out of acquireSAXParser() if acquireSAXParser() is called on a thread that is interrupted (i.e. the InterruptedException is handled in the following code):

    private static SAXParser acquireSAXParser()
            throws TikaException {
        while (true) {
            SAXParser parser = null;
            try {
                READ_WRITE_LOCK.readLock().lock();
                parser = SAX_PARSERS.poll(10, TimeUnit.MILLISECONDS);
            } catch (InterruptedException e) {
                throw new TikaException("interrupted while waiting for SAXParser", e);
            } finally {
                READ_WRITE_LOCK.readLock().unlock();

            }
            if (parser != null) {
                return parser;
            }
        }
    }

A simple fix would be to check for null before calling releaseParser() in the finally block.

Issue Links

• links to: GitHub Pull Request #274