Re: Detect XML document encodings with SAX

Sebastian wrote:


I tried.

And I can not get it to work either.

SAX detects UTF-8 no matter what it really is.

StAX seems never to detect and W3C DOM seems to
always detect correct.

I can not offer an explanation. Obviously the parsers
need to internally detect correct. Otherwise they
could not parse correct.

Code below.

Arne

====

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;

import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.ext.Locator2;
import org.xml.sax.helpers.XMLReaderFactory;
import org.xml.sax.helpers.DefaultHandler;

public class XmlEncodingDectect {
    private static final String FNM1 = "/work/foobar1.xml";
    private static final String FNM2 = "/work/foobar2.xml";
    private static final String FNM3 = "/work/foobar3.xml";
    private static void gen1() throws IOException {
        PrintWriter pw = new PrintWriter(new FileWriter(FNM1));
        pw.println("<?xml version='1.0' encoding='UTF-8'?>");
        pw.println("<root/>");
        pw.close();
    }
    private static void gen2() throws IOException {
        PrintWriter pw = new PrintWriter(new FileWriter(FNM2));
        pw.println("<?xml version='1.0' encoding='ISO-8859-1'?>");
        pw.println("<root/>");
        pw.close();
    }
    private static void gen3() throws IOException {
        PrintWriter pw = new PrintWriter(new FileWriter(FNM3));
        pw.println("<?xml version='1.0'?>");
        pw.println("<root/>");
        pw.close();
    }
    private static String encoding;
    private static String detectSAX(String fnm) throws SAXException,
IOException {
         XMLReader parser = XMLReaderFactory.createXMLReader();
         parser.setContentHandler(new DefaultHandler() {
            private Locator2 locator;
             @Override
             public void setDocumentLocator(Locator locator) {
                 if (locator instanceof Locator2) {
                     this.locator = (Locator2) locator;
                 } else {
                     encoding = "Unknown";
                 }
             }
             @Override
             public void startDocument() throws SAXException {
                 if (locator != null) {
                     encoding = locator.getEncoding();
                 }
             }
         });
         parser.parse(new InputSource(new FileInputStream(fnm)));
         return encoding;
    }
    private static String detectW3CDOM(String fnm) throws
ParserConfigurationException, FileNotFoundException, SAXException,
IOException {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document doc = db.parse(new InputSource(new FileInputStream(fnm)));
         String encoding = doc.getXmlEncoding();
         return encoding != null ? encoding : "Unknown";
    }
    private static String detectStAX(String fnm) throws
FileNotFoundException, XMLStreamException {
        XMLInputFactory xif = XMLInputFactory.newInstance();
         XMLStreamReader xsr = xif.createXMLStreamReader(new
FileInputStream(fnm));
         String encoding = null;
         while(xsr.hasNext()) {
          xsr.next();
             switch(xsr.getEventType()) {
                 case XMLStreamReader.START_DOCUMENT:
                  encoding = xsr.getEncoding();
                  break;
                 default:
                  break;
             }
         }
         return encoding != null ? encoding : "Unknown";
    }
    public static void main(String[] args) throws IOException,
SAXException, ParserConfigurationException, XMLStreamException {
        gen1();
        System.out.println(detectSAX(FNM1));
        System.out.println(detectW3CDOM(FNM1));
        System.out.println(detectStAX(FNM1));
        gen2();
        System.out.println(detectSAX(FNM2));
        System.out.println(detectW3CDOM(FNM2));
        System.out.println(detectStAX(FNM2));
        gen3();
        System.out.println(detectSAX(FNM3));
        System.out.println(detectW3CDOM(FNM3));
        System.out.println(detectStAX(FNM3));
    }
}