java.lang.IllegalArgumentException: Not supported: indent-number

Question

public String filter(String message) {
    if (message == null) {
        return null;
    }

    // Remove formatting, transformer fails to handle wrong indentation correctly.
    message = message.replaceAll(">\\s*[\\r\\n]+\\s*", ">");
    message = message.replaceAll("\\s*[\\r\\n]+\\s*", " "); // for wrapped attribute lists

    Source xmlInput = new StreamSource(new StringReader(message));
    StringWriter stringWriter = new StringWriter();
    try {
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        transformerFactory.setAttribute("indent-number", INDENT); // for Java 6

        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", INDENT.toString()); // Java 1.5
        transformer.transform(xmlInput, new StreamResult(stringWriter));

        String pretty = stringWriter.toString();
        pretty = pretty.replace("\r\n", "\n");
        return pretty;
    } catch (TransformerException e) {
        if (e.getCause() != null && e.getCause() instanceof SAXParseException) {
            return message;
        }
        throw new RuntimeException(e);
    }
}

but i get exception here:

transformerFactory.setAttribute("indent-number", INDENT); // for Java 6

java.lang.IllegalArgumentException: Not supported: indent-number

my java:

java version "1.6.0_33"

why i get this error?

Answer 1

I fixed that exception by commenting this line:

transformerFactory.setAttribute("indent-number", indent);

and adding this line:

transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");

The exception is gone even though the indetation that appears in the browser is incorrect.