FULL PRODUCT VERSION :
java version "1.6.0-rc"
Java(TM) SE Runtime Environment (build 1.6.0-rc-b92)
Java HotSpot(TM) Client VM (build 1.6.0-rc-b92, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
Since b90 there seems to be a check in StAX if the encoding declared in the XML matchs the encoding of the output stream. Unfortunately, if ISO-8859-1 is used as encoding the string for the encoding of the stream is internally transformed and thus the check fails with an exception.

REGRESSION. Last worked in version mustang

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
run following code:
String ENCODING = "ISO-8859-1";
OutputStream out = new ByteArrayOutputStream();
XMLOutputFactory factory = XMLOutputFactory.newInstance();
XMLStreamWriter writer = factory.createXMLStreamWriter(out, ENCODING);
writer.writeStartDocument(ENCODING, "1.0");


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
no exception
ACTUAL -
XMLStreamException

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" javax.xml.stream.XMLStreamException: Underlying stream encoding 'ISO8859_1' and input paramter for writeStartDocument() method 'ISO-8859-1' do not match.
at com.sun.xml.internal.stream.writers.XMLStreamWriterImpl.writeStartDocument(XMLStreamWriterImpl.java:1170)
at StaxTest.main(StaxTest.java:15)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.io.ByteArrayOutputStream;
import java.io.OutputStream;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

public class StaxTest {
    private static final String ENCODING = "ISO-8859-1";

    public static void main(String[] args) throws XMLStreamException {
OutputStream out = new ByteArrayOutputStream();
XMLOutputFactory factory = XMLOutputFactory.newInstance();
XMLStreamWriter writer = factory.createXMLStreamWriter(out, ENCODING);
writer.writeStartDocument(ENCODING, "1.0");
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
use an other encoding e.g. utf-8