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From Saliya Ekanayake <esal...@gmail.com>
Subject Re: XPath evaluation doesn't work on resources picked from registry
Date Sun, 21 Jun 2009 12:01:38 GMT
Hi Indika,

I tested your point and found the cause. Simply, in the second case there is
no parent for the root element. Therefore, evaluating an XPath containing
<hello> element will cause an exception. But if you evaluate an XPath like,
//anotherthing/insideanother, you will get the desired result.

So the solution I would like to suggest in this case is to first check the
parent of the element. If the parent is an instance of OMDocument then we
need not detach (if you need to build then just use OMNode#build()). If the
parent is an instance of OMElement then you need to detach since you want
the element to be isolated from the connecting tree.

Thanks,
Saliya

On Sun, Jun 21, 2009 at 11:06 AM, indika kumara <indika.kuma@gmail.com>wrote:

>         Hi Saliya
>
>         Following shown my scenarios.
>
>
>        Scenario 1  - without detach on root element
>
>         String str = "<hello><something>wow
> nice</something><anotherthing><insideanother>great</insideanother></anotherthing></hello>";
>         XMLStreamReader parser = XMLInputFactory.newInstance().
>                 createXMLStreamReader(new
> ByteArrayInputStream(str.getBytes()));
>         StAXOMBuilder builder = new StAXOMBuilder(parser);
>         OMElement root = builder.getDocumentElement();
> *//        root.detach();*
>
>         AXIOMXPath xpath = new AXIOMXPath("//hello/something");
>         OMElement node = (OMElement) xpath.selectSingleNode(root);
>         System.out.println(node == null);
>         if (node != null) {
>             System.out.println(node.getText());
>         }
>
>
>       Out put :
>
>        false
>       * wow nice*
>
>
>        Scenario 2 - with  detach on root element
>
>         String str = "<hello><something>wow
> nice</something><anotherthing><insideanother>great</insideanother></anotherthing></hello>";
>         XMLStreamReader parser = XMLInputFactory.newInstance().
>                 createXMLStreamReader(new
> ByteArrayInputStream(str.getBytes()));
>         StAXOMBuilder builder = new StAXOMBuilder(parser);
>         OMElement root = builder.getDocumentElement();
>       *  root.detach();*
>
>         AXIOMXPath xpath = new AXIOMXPath("//hello/something");
>         OMElement node = (OMElement) xpath.selectSingleNode(root);
>         System.out.println(node == null);
>         if (node != null) {
>             System.out.println(node.getText());
>         }
>
>        Output
>
>        true
>
>
>    In second case , XPath  have not been evaluated correctly.
>
> Thanks
> Indika
>
> On Sat, Jun 20, 2009 at 9:40 PM, Saliya Ekanayake <esaliya@gmail.com>wrote:
>
>> Hi,
>>
>> Um, I am not really clarified with the problem here. I agree that the full
>> tree should be built before we can evaluate XPath. Adding the element to a
>> new OMDocument, however, just to get this done seems not right.
>> Additionally, the original OMDocument created by the builder will be there
>> even if you detach the element. Detach will only remove the element from the
>> tree to which it belongs. To check this, you can get the builder from the
>> detached element and ask for the OMDocument.  IMHO, we can call
>> result.build() if necessary.
>>
>> Btw. I am not clear why XPath doesn't work on the detached element. I did
>> a simple test as follows and XPath worked, may be I have missed something
>> (please let me know if so).
>>
>>     public static void main(String[] args) throws XMLStreamException,
>> JaxenException {
>>         String str = "<hello><something>wow
>> nice</something><anotherthing><insideanother>great</insideanother></anotherthing></hello>";
>>         StAXOMBuilder builder = new StAXOMBuilder(new
>> ByteArrayInputStream(str.getBytes()));
>>         OMElement root = builder.getDocumentElement();
>>
>>         OMDocument doc = builder.getDocument();
>>         System.out.println(doc == null);
>>
>>         OMElement anotherthing = root.getFirstChildWithName(new
>> QName("anotherthing"));
>>         anotherthing.detach();
>>
>>         doc = ((StAXOMBuilder)anotherthing.getBuilder()).getDocument();
>>         System.out.println(doc == null);
>>
>>         AXIOMXPath xpath = new AXIOMXPath("//insideanother");
>>         OMElement node = (OMElement) xpath.selectSingleNode(anotherthing);
>>         System.out.println(node.getText());
>>     }
>>
>> Thanks,
>> Saliya
>>
>> On Sat, Jun 20, 2009 at 4:45 AM, Andreas Veithen <
>> andreas.veithen@gmail.com> wrote:
>>
>>> StAXOMBuilder actually already creates an OMDocument (which can be
>>> retrieved by the getDocument method). The important thing is that we
>>> need to make sure that the Axiom tree is fully built before closing
>>> the input stream. I guess that the detach method is used because it
>>> has the side effect of fully building the element and because
>>> OMDocument has no method to build the entire tree (see WSCOMMONS-479).
>>>
>>> This gives us two solutions:
>>>
>>> - Use StAXOMBuilder#getDocument and iterate over its children to make
>>> sure the document is fully built.
>>> - Continue to use "detach" and add the element to a new document, as
>>> you suggested. Note that you should not use OMDocumentImpl directly,
>>> but create it using the OMFactory.
>>>
>>> Andreas
>>>
>>> On Fri, Jun 19, 2009 at 09:30, indika kumara<indika.kuma@gmail.com>
>>> wrote:
>>> > Devs
>>> >
>>> > $subject is due to we do  'detach()'  on picked resource OMElement .
>>> > If I add detached element to a OMDocument as a child, it works
>>> >
>>> > Existing code  SImpleURLRegistry
>>> >
>>> > result.detach();
>>> > inputStream.close();
>>> >
>>> >
>>> > Modified code
>>> >
>>> > result.detach();
>>> > OMDocumentImpl omDocument = new OMDocumentImpl();
>>> > omDocument.addChild(result);
>>> > inputStream.close();
>>> >
>>> >
>>> > Are there any best solution other than what I did ?  I haven't deep
>>> > AXIOM knowledge?  Could anyone help me?
>>> >
>>> > Thanks
>>> > Indika
>>> >
>>> > ---------------------------------------------------------------------
>>> > To unsubscribe, e-mail: dev-unsubscribe@synapse.apache.org
>>> > For additional commands, e-mail: dev-help@synapse.apache.org
>>> >
>>> >
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: dev-unsubscribe@synapse.apache.org
>>> For additional commands, e-mail: dev-help@synapse.apache.org
>>>
>>>
>>
>>
>> --
>> Saliya Ekanayake
>> http://www.esaliya.blogspot.com
>> http://www.esaliya.wordpress.com
>>
>
>


-- 
Saliya Ekanayake
http://www.esaliya.blogspot.com
http://www.esaliya.wordpress.com

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