Edit an XML file with SAX

Question

Dear all, I am so confused�.
I have been trying for the last few days to understand how sax works� The only thing I understood is:
DefaultHandler handler = new Echo01();
SAXParserFactory factory = SAXParserFactory.newInstance();
        try {
            out = new OutputStreamWriter(System.out, "UTF8");
            SAXParser saxParser = factory.newSAXParser();
            saxParser.parse(file , handler);
        } catch (Throwable t) {
            t.printStackTrace();
        System.exit(0);
    }Ok, I assign the SAXParser the xml file and a handler. The parser parses and throws events that the handler catches. By implementing some handler interface or overriding the methods of an existing handler (e.g DeafultHandler class) I get to do stuff�
But still, suppose I have implement startElement() method of DefaultHandler class and I know that the pointer is currently placed on an element e.g. <name>bob</name>. How do I get the value of the element, and if I manage to do that, how can I replace�bob� with �tom�?
I would really appreciate any help given� just don�t recommend http://java.sun.com/webservices/jaxp/dist/1.1/docs/tutorial/ because although there are interesting staff in there, it does not solve my problem�

Answer 1

Maybe SAX is not the right tool for you.
With SAX, you implement methods like startElement and characters that get called as XML data is encountered by the parser. If you want to catch it or not, the SAX parser does not care. In your case, the "bob" part will be passed in one or more calls to characters. To safely process the data, you need to do something like build a StringBuffer or StringBuilder in the constructor of the class, and then in the startElement, if the name is one you want to read, set the length to zero. In the characters method, append the data to the StringBuilder or StringBuffer. In the endElement, do a toString to keep the data wherever you want.
This works for simple XML, but may need to be enhanced if you have nested elements with string values that contain other elements.
On the other hand, if your file is not huge, you could use DOM. With DOM, (or with JDOM, and I would expect with Dom4J -- but I have only used the first two) you do a parse and get a Document object with the entire tree. That allows you to easily (at least it is easy once you figure out how to do it) find a node like the "name" element and change the Text object that is its child from a value of "bob" to "tom". With DOM, you can then serialize the modified Document tree and save it as an XML file. SAX does not have any way to save your data. That burden falls to you entirely.
Dave Patterson