user defaulthandler2 and xml serializer

[Lingzhi Zhang <lz...@gmail.com>]

Hi,

I am trying to XML serializer to format a XML file that I frequently change.
I want to keep everything in the original document there (e.g. comment),
just use the XML serializer to format the document. I found that using
DefaultHandler2 has a comment callback, however, it seems that it didn't
work, since i didn't see anything is printed in that method. Other than
that, if I get the comment() call back, how can I make the ContentHandler to
write the comment into output stream. Any hint would be appreciated.

Steve.

My code is like:


package xml;

import java.io.FileOutputStream;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.apache.xml.serialize.OutputFormat;
import org.apache.xml.serialize.XMLSerializer;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
//import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.ext.DefaultHandler2;

/**
 * A writer which parses XML file and output it as standard indented format
 * @author lingzhi.zhang
 *
 */
public class XercesXMLWriter extends DefaultHandler2
{
 private static ContentHandler hd;
 public static void main(String[] args)
 {
  if(args.length != 1)
  {
   System.err.println("Usage: cmd filename");
            System.exit(1);
  }

  // initialize and start Serialization
  try
  {
   FileOutputStream fos = new FileOutputStream(args[0] + ".new");
   OutputFormat of = new OutputFormat("XML","UTF-8",true);
   of.setIndent(1);
   of.setIndenting(true);
//   of.setDoctype(null,"users.dtd");
   XMLSerializer serializer = new XMLSerializer(fos,of);
   hd = serializer.asContentHandler();
  } catch (Throwable t) {
   t.printStackTrace();
  }

  // initialize and start parser
  try
  {
      SAXParserFactory factory = SAXParserFactory.newInstance();
      SAXParser parser = factory.newSAXParser();
      DefaultHandler2 handler = new XercesXMLWriter();
      parser.parse(args[0], handler);
  }
  catch (Throwable t)
  {
   t.printStackTrace();
  }
  System.exit(0);
 }

 public void startDocument() throws SAXException
 {
  hd.startDocument();
 }

 public void startElement(String namespaceURI,
                String lName, // local name
                String qName, // qualified name
                Attributes attrs)
 throws SAXException
 {
  hd.startElement(namespaceURI, lName, qName, attrs);
 }

 public void character(char buf[], int offset, int len)
 throws SAXException
 {
  hd.characters(buf, offset, len);
 }

 public void endElement(String namespaceURI,
       String sName, // simple name
       String qName  // qualified name
             )
 throws SAXException
 {
  hd.endElement(namespaceURI, sName, qName);
 }

 public void endDocument() throws SAXException
 {
  hd.endDocument();
 }

 public void comment(char[] ch, int start, int length)
 throws SAXException
 {
  System.out.println("comment");
 }
}

Re: user defaulthandler2 and xml serializer

[Klaus Malorny <Kl...@knipp.de>]

Lingzhi Zhang wrote:
> Hi,
>  
> I am trying to XML serializer to format a XML file that I frequently 
> change. I want to keep everything in the original document there (e.g. 
> comment), just use the XML serializer to format the document. I found 
> that using DefaultHandler2 has a comment callback, however, it seems 
> that it didn't work, since i didn't see anything is printed in that 
> method. Other than that, if I get the comment() call back, how can I 
> make the ContentHandler to write the comment into output stream. Any 
> hint would be appreciated.
>  
> Steve.
>  
> My code is like:
>  
> 

Hi,

as far as I understand this, DefaultHandler2 implements the LexicalHandler 
interface which contains the requested method. However, the parse method only 
takes a DefaultHandler and is therefore unaware of the implemented 
LexicalHandler interface. So IMHO you have to explicitly tell the parser about 
an implementation of LexicalHandler via the Parser.setProperty method, i.e.

   parser.setProperty ("http://xml.org/sax/properties/lexical-handler", handler);

just before calling the parse method. See also the JavaDoc for the 
org.xml.sax.ext.LexicalHandler interface. By the way, the XMLSerializer also 
implements the LexicalHandler interface, so you could directly specify it in the 
setProperty call and your adapter class wouldn't need to take care of it.

greetings,

Klaus

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