Howto let the SAX parser determine the encoding from the xml declaration?

Question

Hi,

I'm trying to parse xml files from different sources (over which I have little control). Most of the them are encoded in UTF-8 and don't cause any problems using the following snippet:

SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
FeedHandler handler = new FeedHandler();
InputSource is = new InputSource(getInputStream());
parser.parse(is, handler);

Since SAX defaults to UTF-8 this is fine. However some of the documents declare:

<?xml version="1.0" encoding="ISO-8859-1"?>

Even though ISO-8859-1 is declared SAX still defaults to UTF-8. Only if I add:

is.setEncoding("ISO-8859-1");

Will SAX use the correct encoding.

How can I let SAX automatically detect the correct encoding from the xml declaration without me specifically setting it? I need this because I don't know before hand what the encoding of the file will be.

Thanks in advance, Allan

Answer 1

I found the answer myself.

The SAX parser uses InputSource internally and from the InputSource docs:

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.

So basically you need to pass a character stream to the parser for it to pick-up the correct encoding. See solution below:

SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
FeedHandler handler = new FeedHandler();
Reader isr = new InputStreamReader(getInputStream());
InputSource is = new InputSource();
is.setCharacterStream(isr);
parser.parse(is, handler);