[jdom-interest] Comment and ProcessingInstruction parents

[Elliotte Rusty Harold]

I'm repeating this suggestion from April. At the time Bradley 
Huffman, agreed that it was a good idea. I don't think anyone else 
commented one way or the other. I've implemented this for Comment. It 
would be hard to implement it for the other classes.

The Comment and ProcessingInstruction classes appear to be deeply 
schizophrenic about who can be their parents, specifically whether or 
not a Document is allowed as a parent of one of these. (This is legal 
in normal XML temrinology. A typical xml-stylesheet processing 
instruction in the prolog would be considered to have the document 
itself as its parent.)

For example, in ProcessingInstruction the parent field is declared to 
have type Object:

    /** Parent element, document, or null if none */
    protected Object parent;

However, setParent() and getParent() only allow elements as parents:

    /**
     * <p>
     * This will return the parent of this <code>ProcessingInstruction</code>.
     *   If there is no parent, then this returns <code>null</code>.
     * </p>
     *
     * @return parent of this <code>ProcessingInstruction</code>
     */
    public Element getParent() {
        if (parent instanceof Element) {
            return (Element) parent;
        }
        return null;
    }

    /**
     * <p>
     * This will set the parent of this <code>ProcessingInstruction</code>.
     * </p>
     *
     * @param parent <code>Element</code> to be new parent.
     * @return this <code>ProcessingInstruction</code> modified.
     */
    protected ProcessingInstruction setParent(Element parent) {
        this.parent = parent;
        return this;
    }

One of these needs to be fixed, and I think it's setParent() and 
getParent(). Processing instructions and comments do appear with the 
document itself as the natural parent. We need to support that.


-- 
+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | elharo at metalab.unc.edu | Writer/Programmer |
+-----------------------+------------------------+-------------------+ 
|           The XML Bible, 2nd Edition (IDG Books, 2001)             |
|             http://www.cafeconleche.org/books/bible2/              |
|   http://www.amazon.com/exec/obidos/ISBN=0764547607/cafeaulaitA/   |
+----------------------------------+---------------------------------+
|  Read Cafe au Lait for Java News:   http://www.cafeaulait.org/ 
| |  Read Cafe con Leche for XML News:  http://www.cafeconleche.org/ 
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-- 

+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | elharo at metalab.unc.edu | Writer/Programmer |
+-----------------------+------------------------+-------------------+
|           Processing XML with Java (Addison-Wesley, 2002)          |
|              http://www.cafeconleche.org/books/xmljava             |
| http://www.amazon.com/exec/obidos/ISBN%3D0201771861/cafeaulaitA  |
+----------------------------------+---------------------------------+
|  Read Cafe au Lait for Java News:  http://www.cafeaulait.org/      |
|  Read Cafe con Leche for XML News: http://www.cafeconleche.org/    |
+----------------------------------+---------------------------------+