Java and XML, Second Edition

Error Handlers

In addition to providing the ContentHandler interface for handling parsing events, SAX provides an ErrorHandler interface that can be implemented to treat various error conditions that may arise during parsing. This class works in the same manner as the document handler already constructed, but defines only three callback methods. Through these three methods, all possible error conditions are handled and reported by SAX parsers. Here’s a look at the ErrorHandler interface:

public interface ErrorHandler {
    public abstract void warning (SAXParseException exception)
		throws SAXException;
    public abstract void error (SAXParseException exception)
		throws SAXException;
    public abstract void fatalError (SAXParseException exception)
		throws SAXException;
}

Each method receives information about the error or warning that has occurred through a SAXParseException. This object holds the line number where the trouble was encountered, the URI of the document being treated (which could be the parsed document or an external reference within that document), and normal exception details such as a message and a printable stack trace. In addition, each method can throw a SAXException. This may seem a bit odd at first; an exception handler that throws an exception? Keep in mind that each handler receives a parsing exception. This can be a warning that should not cause the parsing process to stop or an error that needs to be resolved for parsing to continue; however, the callback may need ...