The SAX parser will use the InputSource object to determine how to read XML input. If there is a character stream available, the parser will read that stream directly, disregarding any text encoding declaration found in that stream. If there is no character stream, but there is a byte stream, the parser will use that byte stream, using the encoding specified in the InputSource or else (if no encoding is specified) autodetecting the character encoding using an algorithm such as the one in the XML specification. If neither a character stream nor a byte stream is available, the parser will attempt to open a URI connection to the resource identified by the system identifier.
http://www.kdgregory.com/index.php?page=xml.parsing
http://stackoverflow.com/questions/3482494/howto-let-the-sax-parser-determine-the-encoding-from-the-xml-declaration
http://www.saxproject.org/apidoc/org/xml/sax/InputSource.html