According to "Easy and Efficient XML Processing" article (http://java.sun.com/developer/technicalArticles/xml/jaxp1-3/):
Is it possible to use the same parser instance to parse multiple XML documents? This was not clear, and the behavior was implementation dependent.
In case Xerces is being used as a parser, it seems to be safe. Xerces parser class org.apache.xerces.parsers.SAXParser implements org.xml.sax.XMLReader, which in turn is safe for reuse (according to javadoc):
Once a parse is complete, an application may reuse the same XMLReader object, possibly with a different input source.