Creating and Modifying XML Documents - Beginning Java - page 1310

JOptionPane.showMessageDialog(this,
"Parser configuration error while creating

document",

"DOM Parser Error",
JOptionPane.ERROR_MESSAGE);
System.err.println(pce.getMessage());
pce.printStackTrace();
return null;
} catch(DOMException de) {
JOptionPane.showInternalMessageDialog(null,
"DOM exception thrown while creating

document",

"DOM Error",
JOptionPane.ERROR_MESSAGE);
System.err.println(de.getMessage());
de.printStackTrace();
return null;

}

// Each element in the sketch can create its own node in the document
SketcherModel elements = theApp.getModel(); // Get the sketch
for(Element element : elements) { // For each element...

element.addElementNode(doc); // ...add its node.

}
return doc;

}

Directory "Sketcher reading and writing XML"

Notice that this assumes that the DTD file for Sketcher should be in your Beg Java Stuff folder. If it
isn't, amend the code accordingly. You call setErrorHandler() for the DocumentBuilder object to make
the SketcherFrame object the handler for parsing errors. This implies that you must make the Sketcher-
Frame class implement the ErrorHandler interface.
You pop up a dialog and return null if something goes wrong when you are creating the Document object.
In case of a DOMException being thrown, you could add a switch statement to analyze the value in the code
member of the exception and provide a more specific message in the dialog.
To implement the ErrorHandler interface, first amend the first line of the SketcherFrame class defini-
tion:
public class SketcherFrame extends JFrame
implements ActionListener, Observer, Printable, ErrorHandler {

Now you can add the following three method definitions that are required:

// Handles recoverable errors from parsing XML
public void error(SAXParseException spe) {
JOptionPane.showMessageDialog(SketcherFrame.this,
"Error at line " + spe.getLineNumber() + "\n" +

spe.getMessage(),