I isolated the concurrency failures to two places. First, SAXParserFactories are not guaranteed to be thread-safe, so I synchronized the saxFactory.newSAXParser() call.
Second, and much more major - we are apparently "sharing" instances of SimpleDeserializers....?!? I don't understand how this could work in a multi-threaded environment, when each deserializer is maintaining a StringBuffer collecting values from deserialized XML.... I propose we remove all of the code related to sharing deserializers. Serializers may be shared, since they don't have state, but Deserializers must be created on a per-instance basis, or must be redesigned to hold state in TLS or some other thread-safe place. I may be missing something here, so please fill me in if you think this is an incorrect analysis. I will note that turning off sharing in all cases has fixed the concurrency test problems. Sorry for not noticing and commenting on this earlier. --Glen
