I am attempting to generate HTML within my application for printing
documents.  Due to various restrictions, I am using the
javax.swing.text.html.HTMLDocument package.  That can't change (unless
it is impossible to do what I want to do).

My method takes in a TableModel and attempts to create an HTML
document from the data in the table, replicating the table within HTML
code.  However, when I run the method below, I get the following
exception:

javax.swing.text.StateInvariantError: Illegal cast to
MutableAttributeSet
    at javax.swing.text.AbstractDocument
$AbstractElement.checkForIllegalCast(AbstractDocument.java:2055)
    at javax.swing.text.AbstractDocument
$AbstractElement.addAttributes(AbstractDocument.java:1988)
    at javax.swing.text.AbstractDocument
$AbstractElement.<init>(AbstractDocument.java:1781)
    at javax.swing.text.AbstractDocument
$BranchElement.<init>(AbstractDocument.java:2248)
    at javax.swing.text.html.HTMLDocument
$BlockElement.<init>(HTMLDocument.java:3674)
    at
javax.swing.text.html.HTMLDocument.createBranchElement(HTMLDocument.java:
379)
    at
hasrd.gui.components.print.HasrdDocument.generateHTML(MyHTMLDocumentGenerator.java:
152)
       ...

Is it even possible to do what I want to do?  If so, what am I doing
wrong?

Thanks

Here is the method in question.  It is self-contained.

   protected void generateHTML(TableModel dataTable) {
       AbstractDocument.AttributeContext ctx = getAttributeContext();

       // create default root element
       BranchElement root = (BranchElement) this.createDefaultRoot();

       // create the table
       AttributeSet atts = ctx.getEmptySet();
       atts = ctx.addAttribute(atts, StyleConstants.NameAttribute,
               HTML.Tag.TABLE);
       BranchElement table = (BranchElement)
createBranchElement(root, atts); // ERROR HAPPENS HERE
       root.replace(0, 0, new Element[] { table });

       // for each row in the table, add a row to the html
       for (int row = 0; row < dataTable.getRowCount(); row++) {
           // create the table
           atts = ctx.getEmptySet();
           atts = ctx.addAttribute(atts,
StyleConstants.NameAttribute,
                   HTML.Tag.TR);
           BranchElement rowTag = (BranchElement)
createBranchElement(table,
                   atts);
           table.replace(0, 0, new Element[] { rowTag });

           // for each column
           for (int col = 0; col < dataTable.getColumnCount(); col++)
{
               // create the cell
               atts = ctx.getEmptySet();
               atts = ctx.addAttribute(atts,
StyleConstants.NameAttribute,
                       HTML.Tag.TD);
               BranchElement cellTag = (BranchElement)
createBranchElement(
                       rowTag, atts);
               rowTag.replace(0, 0, new Element[] { cellTag });

               // put data into leaf node
               atts = ctx.getEmptySet();
               atts = ctx.addAttribute(atts,
StyleConstants.NameAttribute,
                       HTML.Tag.CONTENT);
               atts = ctx.addAttribute(atts,
                       StyleConstants.ComposedTextAttribute,
dataTable
                               .getValueAt(row, col));
               Element leaf = createLeafElement(cellTag, atts, 0, 1);
               cellTag.replace(0, 0, new Element[] { leaf });
           }
       }
   }