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From Yau Lawrence <Lawrence....@nc3a.nato.int>
Subject RE: [SCXML] - XPATH
Date Thu, 05 Jun 2008 09:19:13 GMT
Hello Pascal,
The simplest way to correct the problem is to change your datamodel definition to use an unnamed
namespace for your poolconfiguration XML tree:

...
<data name="poolconfiguration">
        <foo xmlns="">  <!-- override SCXML namespace -->
                <dir>toto</dir>
                <freq>1</freq>
        </foo>
</data>
...

Then your xpath expression will work.  I tested your SCXML document just to be sure.

Hope this helps,
Lawrence


-----Original Message-----
From: Pascal Ravot [mailto:pascal.ravot@mcc-soft.com]
Sent: 05 June 2008 9:26
To: user@commons.apache.org
Subject: SCXML - XPATH

Hello,
I'm a perfect newbie to sxcml, so i'm probably asking stupid questions !

I'm trying to get access to the content of a datamodel from within the scxml document and
a custom action :
Here is the dummy state machine:

     <scxml xmlns="http://www.w3.org/2005/07/scxml" version="1.0"
         xmlns:mc="http://com.mccsoft.scxml/action" initialstate="start">
         <!--  Defining global data  -->
         <datamodel>
             <data name="timeout" expr="1" />
             <data name="counter" expr="1" />
             <data name="poolconfiguration">
                 <foo>
                     <dir>toto</dir>
                     <freq>1</freq>
                 </foo>
             </data>
         </datamodel>
         <!-- State machine starts here -->
         <state id="start">
             <onentry>
                 <log
                     expr="Data(poolconfiguration, 'foo/dir')"
                 />
             </onentry>
             <transition target="now_waiting" />
         </state>
         <state id="now_waiting">
             <onentry>
                 <log expr="Counter is now counter" />
             </onentry>
             <onentry>
                 <mc:wait timeoutName="timeout" conf="poolconfiguration"/>
                 <assign name="counter" expr="counter +1" />
                 <log
                     expr="'Timeout is ' + timeout + ' Counter is ' + counter " />
             </onentry>
             <transition target="now_waiting" />
         </state>

     </scxml>

Regarding execution environment everything is copied from samples  using Jexl :

             exec = new SCXMLExecutor(new JexlEvaluator(),
                     new SimpleDispatcher(), new SimpleErrorReporter());
             exec.setStateMachine(scxml);
             exec.setRootContext(new JexlContext());

I've got a custom action <mc:wait ...> that get the name of the data entry to inspect...
Within the execute of the action i'm trying to do roughly but with java the equivalent of
<log expr="Data(poolconfiguration, 'foo/dir')" />

-->
         scInstance.getEvaluator().eval(
                     scInstance.getRootContext(), "Data(" + conf + ",'foo/dir')");


My objective is to be able to access sub elements of a defined data (in this case poolconfiguration/foo/dir)
of a top level datamodel.
and that either by scxml script or within custom action.

Unfortunately, none of those evaluation is returning the expected "toto".

I got in the log :
1922 [main] DEBUG org.apache.commons.jexl.ExpressionFactory  - Parsing
expression: _builtin.data(_ALL_NAMESPACES, poolconfiguration, 'foo/dir'); 4500 [main] WARN
org.apache.commons.scxml.Builtin  - Data(): No nodes matching the XPath expression "foo/dir",
returning null

or
126125 [main] DEBUG org.apache.commons.scxml.Builtin  - Turning off namespaced XPath evaluation
since no namespace information is available for path: foo/dir 126140 [main] WARN org.apache.commons.scxml.Builtin
 - Data(): No nodes matching the XPath expression "foo/dir", returning null

(for the custom action).

The strange point is that, after debugging this sample, it appeared that the poolconfiguration
node is correctly extracted by the Data expression. I mean the datanode found in the _builtin
seems ok (with childs, sieblings...), but this piece of code  (org.apache.commons.scxml.Builtin.java):
result = XPathAPI.selectNodeList(dataNode, path); returns an empty list.

It is most obvious (to everybody except me) that i've probably spelled the XPATH in an incorrect
way, but i've tried may path without success ( '//dir', '/data/foo/dir',
'data/foo/dir'...)

So any help or idea is welcomed !!!!

By advance thanks.

P. Ravot.

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