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Date: Mon, 1 Dec 2008 08:49:37 +1030
From: "Andrew Hughes" <ahhughes@gmail.com>
To: "Commons Users List" <user@commons.apache.org>
Subject: Re: JXPath XBeanInfo & Generic Collection Problem
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Does JXPath still have an active user/development base? I've seen very
little traffic on this list. This still does not work and I've no idea why.

On Tue, Nov 25, 2008 at 11:05 AM, Andrew Hughes <ahhughes@gmail.com> wrote:

> Everything falls apart once collections or array's are involved. I am doing
> something wrong, help would be most appreciated. I can't see any simple
> examples online and there's no doco on how to do this.
> I'm considering giving up, like the rest of the people before me.
>
> On Mon, Nov 24, 2008 at 12:28 PM, Andrew Hughes <ahhughes@gmail.com>wrote:
>
>> After further testing, I have reduced the complexity of my 'Bean'. The
>> 'Bean' is no longer a Collection<> and provides getThe* methods that do not
>> meet the Beans standard. Hence, JXPath must use an XBeanInfo and
>> DynamicHandler to perform sucessful traversal/evalution, and it does...
>> For the first time I can see  DynamicHandler<init> being called. My
>> previous DynamicHandler that worked with a Collection class was never
>> initialized and thus proves JXPath was never using it.
>>
>> The big question is, why? I know I can get around this by reworking my
>> datastructure so that it does not extend ArrayList<MyBean> () but I really
>> don't think I should have to do this.
>>
>> I've read a few posts with the same problem now (some as far back as
>> 2006). Im yet to see a solution, it looks like everyone else just decides to
>> 'give up' which I'd rather not do, because if this works it's a great
>> solution.
>>
>> :)
>>
>>
>> On Mon, Nov 24, 2008 at 9:49 AM, Andrew Hughes <ahhughes@gmail.com>wrote:
>>
>>> After a little more investigation, I have overriden every
>>> Collection/ArrayList method in the "PojoNode" class to see how/if JXPath
>>> calls ANY of the inherited super methods. It does not! If JXPath is not
>>> traversing my data structure in any way, then it's probably not even
>>> evaluating it. But Im not sure why this would be, or why under such
>>> circumstances a mis-configuration like this does not throw any exceptions.
>>> As I said, I think I have exhausted the online docs and I'm getting a
>>> little desperate (probably sound like it too). So any help would definitely
>>> be appreciated. :)
>>>
>>>
>>> On Fri, Nov 21, 2008 at 1:42 PM, Andrew Hughes <ahhughes@gmail.com>wrote:
>>>
>>>> Hi,
>>>> I'm trying to work out how I can add the following PojoNode to JXPath's
>>>> context for evaluation.
>>>>
>>>> public class PojoNode extends java.util.ArrayList<PojoNode> {
>>>> public PojoNode(Pojo pojo) {
>>>>  this.pojo = pojo;
>>>>  }
>>>>  private Pojo pojo;
>>>>  public Pojo getPojo() {
>>>>  return pojo;
>>>>  }
>>>> }
>>>>
>>>>
>>>>
>>>> The PojoNode tree above is (definitely) populated... then I setup and
>>>> ask JXPath to evaluate an expression on it:
>>>>
>>>>
>>>> JXPathIntrospector.registerDynamicClass(PojoNode.class,PojoDynamicPropertyHandler.class);
>>>> JXPathContext jxPathContext = JXPathContext.newContext(rootPojoNode);
>>>> PojoNode result = (PojoNode)jxPathContext.getValue("/"); //this always
>>>> produces an empty result
>>>>
>>>>
>>>> What concerns me is not the code I have written but the code I have not.
>>>> I've got log statements in the PojoXInfoBean and PojoDynamicPropertyHandler
>>>> (see below) but none every fire (in particular  "I have been asked to
>>>> look.." and "...w00t").  Consequently the PojoNode tree is not being
>>>> traversed correctly and thus fails. I suspect that because PojoNode
>>>> implements a Collection it's picked up buy another DynamicPropertyHandler.
>>>>
>>>> I feel like I have exhausted the javadocs and any help would be very
>>>> very much appreciated.
>>>>
>>>> Thank You.
>>>>
>>>>
>>>> ps if you wanted to see more code it is below....
>>>>
>>>> public class PojoNodeDynamicPropertyHandler implements
>>>>  DynamicPropertyHandler {
>>>>
>>>> private final static Logger log =
>>>> Logger.getLogger(PojoNodeDynamicPropertyHandler.class);
>>>>
>>>> public Object getProperty(Object PojoNode, String name) {
>>>>  log.debug("I have been asked to look for '"+name+"'");
>>>>  Collection<PojoNode> hits = new ArrayList<PojoNode>();
>>>>  for(PojoNode childPojoNode : (PojoNode) PojoNode){
>>>>  if (childPojoNode.getPojo().getName().equals(name)){
>>>>  hits.add(childPojoNode);
>>>>  }
>>>>  }
>>>>
>>>> log.debug("I have found '"+hits.size()+"' instances of '"+name+"'");
>>>>  return hits;
>>>>  }
>>>>
>>>> public String[] getPropertyNames(Object PojoNode) {
>>>>  log.debug("JXPath has asked for this, w00t!");
>>>>  HashSet<String> nameSet = new HashSet<String>();
>>>>  nameSet.addAll(collectChildNames(PojoNode));
>>>>  return (String[]) nameSet.toArray(new String[nameSet.size()]);
>>>>  }
>>>>
>>>> public void setProperty(Object arg0, String arg1, Object arg2) {
>>>>  throw new RuntimeException(
>>>>  "Manipulation through JXPath is not allowed.... (yet)");
>>>>  }
>>>>
>>>> private HashSet<String> collectChildNames(Object PojoNode) {
>>>>  HashSet<String> nameSet = new HashSet<String>();
>>>>  for (PojoNode childPojo : (PojoNode) PojoNode) {
>>>>  nameSet.add(childPojo.getPojo().getName());
>>>>  }
>>>>  return nameSet;
>>>>  }
>>>>
>>>> }
>>>>
>>>> ........................................................................................
>>>>
>>>> public class PojoNodeXBeanInfo implements JXPathBeanInfo{
>>>>
>>>>   private static final Logger log =
>>>> Logger.getLogger(PojoNodeXBeanInfo.class);
>>>>
>>>>
>>>> public Class<PojoNodeDynamicPropertyHandler>
>>>> getDynamicPropertyHandlerClass() {
>>>>
>>>>  log.debug("JXPath has asked for this, w00t!");
>>>>
>>>>  return PojoNodeDynamicPropertyHandler.class;
>>>>
>>>>  }
>>>>
>>>>
>>>>  public PropertyDescriptor getPropertyDescriptor(String arg0) {
>>>>
>>>>  log.debug("JXPath has asked for this, w00t!");
>>>>
>>>>  return null;
>>>>
>>>> }
>>>>
>>>>
>>>> public PropertyDescriptor[] getPropertyDescriptors() {
>>>>
>>>>  log.debug("JXPath has asked for this, w00t!");
>>>>
>>>>  return null;
>>>>
>>>>  }
>>>>
>>>>
>>>>  public boolean isAtomic() {
>>>>
>>>> log.debug("JXPath has asked for this, w00t!");
>>>>
>>>>  return false;
>>>>
>>>>  }
>>>>
>>>>
>>>>  public boolean isDynamic() {
>>>>
>>>> log.debug("JXPath has asked for this, w00t!");
>>>>
>>>>  return true;
>>>>
>>>>  }
>>>>
>>>>  }
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>
>

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