SAX Parsing And Keeping Track Of Children
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Thread: SAX Parsing And Keeping Track Of Children

  1. #1
    Join Date
    May 2011
    Posts
    6

    Unhappy SAX Parsing And Keeping Track Of Children

    Hi,
    I'm trying to parse a document using SAX for Java. I need to keep track of the parent of the children in an XML format that allows for infinite decendants. I need to keep track of the parent as I go through. When I find the root phase object, I need to create an object in the database, retrieve the ID of the stored object. When I get to the children I need to know who their parent is so I can set their parentID in the database. How do I keep track of the parent? I included an XML file and a diagram showing the hierarchy. If I go all the way down to B_level4, how do I know that B_level2 is the child of A_level1 and not A_level3?

    I was going to:
    - find the first phase and set it to current
    - Get the level below, set current to parent, and set the id to the current

    How do I deal with the infinite depth (having phases within phases) and keeping track of who the parent is?

    Thanks,
    Stan
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  2. #2
    Join Date
    Aug 2011
    Location
    West Yorkshire, U.K.
    Posts
    54

    Re: SAX Parsing And Keeping Track Of Children

    Use a stack - when startElement is called, push a new element on the stack, when endElement is called, pop the stack.

    Attached is some code (incomplete) which SAX parses XML into a Document. (Before anyone asks - so a massive XML document can be processed througn an XSLT in chunks). It uses a stack to keep track of parent elements. I suspect this could easily be adapted to keep track of your database IDs.

    Code:
    import java.util.Stack;
    
    public class MySaxHandler extends DefaultHandler {
    
        // These are all initialised by the constructor (omitted)
        private Document doc = null;
        private Element workingElement = null;
        private Stack workingStack = null;
    
    
        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            // Add element to the document ....
            Element temp = doc.createElement(qName);
            workingElement.appendChild(temp);
            // Push the current working element on the stack ...
            workingStack.push(workingElement);
            // And make the current element the working one
            workingElement = temp;
        }
    
    
        public void endElement(String uri, String localName, String qName) throws SAXException {
            // Pop off the stack ....
            workingElement = (Element)workingStack.pop();
        }
    
    
        public void characters(char[] arg0, int arg1, int arg2) throws SAXException {
            String chars = new String(arg0, arg1, arg2).toUpperCase();
            Text t = doc.createTextNode(chars);
            workingElement.appendChild(t);
        }
    
    
    }

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