Thanks very much for your synchronistic response. I have since resorted to using XML Schema.
I did not have any luck with the properties declared in the Digester class (probably my ignorance), so I used the following instead:
Digester digester = new Digester();
digester.setValidating(true);
digester.setNamespaceAware(true);
digester.setSchemaLanguage("http://www.w3.org/2001/XMLSchema";);
digester.setSchema("wdkModelSchema.xsd");
digester.setErrorHandler(new org.xml.sax.helpers.DefaultHandler());
Unfortunately, the DefaultHandler does not offer the option of terminating on error (instead it logs [ERROR] messages).
So, I am now in search of an ErrorHandler that does that.
Steve
Simon Kitching wrote:
On Sat, 2004-06-05 at 04:31, Steve Fischer wrote:
Hello-
I am new to Digester. I am using it for a simple application.
I would like digester to halt if the XML file contains unexpected tags or attributes. By unexpected I mean that there is no rule matching them. In other words, the file must only contain XML that conforms to my rules.
But, Digester continues past these, and only mentions the problem in the log under DEBUG mode.
Questions:
- can i make digester stop on a no-rule-found condition? (if not, what is the thinking behind why that is not an option?)
- or, do i need to define a DTD for my xml and use validation? If so, what errorHandler should I use?
Hi Steve,
This is definitely a case of "synchronicity" (http://en.wikipedia.org/wiki/Synchronicity)!
I was trying to achieve exactly this effect just yesterday.
In the CVS HEAD version of digester, there is a Rules class called "WithDefaultsRulesWrapper" which allows a set of default rules to be returned if an element is encountered in the input and there are no matching rules. By setting the default rule to be a rule that just throws an exception from its "begin" method the effect we are trying to achieve can be implemented. I got this working yesterday.
This WithDefaultsRulesWrapper class should work fine with the digester-1.5 distribution, so if you don't want to use a complete digester build from CVS you could still extract this class, change the package name, and include it with your app.
I think that this solution could be made a bit more elegant though. I am
looking into whether the WithDefaultsRulesWrapper functionality could
essentially be embedded into the standard RulesBase class. And adding
this custom rule which throws exceptions into the standard Digester
distribution.
Alternatively, a schema could be applied to the input as you mention. I think you will need to call the Digester.setErrorHandler method with an appropriate parameter in order to cause validation errors to terminate processing.
Or, as you suggest, a flag could be added to the Digester to specify whether processing should terminate if no match is found. I think this is not a bad idea. You could of course implement this right now simply by subclassing digester and overriding the startElement method. I believe that this could be done quite elegantly by calling the inherited startElement method, then inspecting the top object on the "matches" stack; if it is null or an empty list then the current input element matched no rules. [NB: not tested...]
If you have any other suggestions about how this could be implemented, please let me know....
Regards,
Simon
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