Re: [validator] Schematron-type/XPath Validator

[Don Brown]

Yeah, I think putting it in contrib as Robert suggested might be a good 
start, however even if it shipped with Validator, it wouldn't be needed 
unless you wanted to use the jxpath validator. XPath is basically an 
expression language to locate nodes. While intended for XML documents, 
JXPath makes it possible to use it with JavaBeans, DynaBeans, and a 
bunch more. In addition to node location syntax, XPath includes various 
functions like the number() one in my example.

A XPath tutorial: 
http://www.zvon.org/xxl/XPathTutorial/General/examples.html
XPath functions: 
http://www.devguru.com/Technologies/xslt/quickref/xslt_index_functions.html

Of course this validator wouldn't be for everyone, particularly those 
with no XPath knowledge, but for those of us that work with it every 
day, it allows us to re-use that knowledge to do complex things quickly 
and efficiently. One less language/syntax to learn is a good thing! :)

Don
David Graham wrote:
This sounds interesting but I don't know anything about XPath so a more in
depth example would be useful.  I'm also worried about adding another
dependency; maybe this could be an optional download?
David
--- Don Brown <[EMAIL PROTECTED]> wrote:
 

I wrote a simple Validator that uses JXPath to implement a 
schematron-style validation where fields are evaluated against boolean 
XPath expressions.  The idea is from the XMLForms project 
(http://www.xmlform.org), previously of Cocoon.  JXPath makes it easy to

write complex validations on many types of objects that can span object 
trees.

The initialization of the validator looks like this:
<validator name="jxpath"
               
classname="org.apache.commons.validator.JXPathValidator"
                method="isValid"
                
methodParams="java.lang.Object,org.apache.commons.validator.Field"
                msg=""/>

and a sample usage:
<field property="value" depends="jxpath">
 <var>
   <var-name>test</var-name>
   <var-value>number(.) > 0 and number(.) &lt; 10</var-value>
 </var>
</field>
The test variable contains the xpath expression to evaluate.  The 
"property" attribute contains the xpath expression to narrow the scope 
of the tested xpath.  Thanks to JXPath, this validator works on many 
different types of Java objects, including JavaBeans, and can handle 
field property xpath expressions that match multiple "nodes" or values.

If this validator would be useful for the commons-validator project, I 
can supply code for the validator, unit tests, and any patches to 
existing files, through bugzilla of course.

Don
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