The way to dynamic validate xml against DTD

Although the apache digester is popular today and also benefit us a lot, but sometimes we still need to validate or parse the xml base on the DTD, for the static validate/parse (most of the case, it is the procedure of reading a configuration file of the Web Application), it is really easy to do, we can just specify the path of the xml and let the SAX or DOM do rest things for us.

But what if you need to validate the xml dynamiclly?(Eg, you received a xml from others and you need to specify the different DTD base on the different case, that is common in a J2EE project)

The following API will handle with such case.

For the SAX

SAXParserFactory factory = SAXParserFactory.newInstance();

factory.setValidating(true); // never forgot this

SAXParser parser = factory.newSAXParser();

XMLReader reader = parser.getXMLReader();

reader.setEntityResolver(##you own error handler##);

reader.setErrorHandler(##you own error handler##);

For the DOM

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

factory.setValidating(true); // never forgot this

DocumentBuilder builder = factory.newDocumentBuilder();

builder.setEntityResolver((##you own error handler##););

builder.setErrorHandler((##you own error handler##););

Be very awear of handling the error correctly in your Handler class, Never Try To Use The DefaultHandler. you may drop into the trap.

look at the java api of the org.xml.sax...DefaultHandler

error

public void error(SAXParseException e)

throws SAXException

Receive notification of a recoverable parser error.

The default implementation does nothing. Application writers may override this method in a subclass to take specific actions for each error, such as inserting the message in a log file or printing it to the console.

Specified by:

error in interface ErrorHandler

you can never image that the sun provide us a api that skip the error handling. that is stupid in most of the case I think. actually, I spend to much time on it today. hope your good luck.