Re: [validator] Schematron-type/XPath Validator

[Don Brown]

Those dependencies are only necessary if you plan to use functionality 
that relies on them.  JXPath has code to work with many different 
objects, like for example JDOM elements, but if you don't use JDOM, then 
you don't need the JDOM dependencies.  I'm not sure about the 
collections dependency, however.

Don
Niall Pemberton wrote:
Given all the recent furore over collections is JXPath's dependency on it
due to Beanutils or does it use collections classes directly?
Also I was surprised JXPath depends on the servlet api and is this a
dependancy validator is OK to inherit?
http://jakarta.apache.org/commons/jxpath/dependencies.html
Niall
----- Original Message ----- 
From: "Don Brown" <[EMAIL PROTECTED]>
To: "Jakarta Commons Developers List" <[EMAIL PROTECTED]>
Sent: Friday, May 21, 2004 5:41 PM
Subject: Re: [validator] Schematron-type/XPath Validator

 

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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