As suggested in SO [1] and discussed in the mailing list [2], I'll activate the unsynchronized mode in the XmlBeans options. [1] https://stackoverflow.com/questions/45082014/ [2] http://apache-poi.1045710.n5.nabble.com/Unsynchronize-xmlbean-calls-td5728316.html
applied via r1803120
Regression tests showed that this causes multi-threading issues when handling different files in separate threads, therefore we cannot apply this generally. Thus this will be reverted for now. Anybody who wants to use this performance tuning in a single-threaded application can do so by adding the following call before invoking any POI related code: org.apache.poi.POIXMLTypeLoader.DEFAULT_XML_OPTIONS.setUnsynchronized();