RE: XMLBookmark question...

Wed, 29 Mar 2006 12:41:50 -0800

Are there any examples of XMLBookmark usage??  I don't seem to be able to get back a bookmark I set, and I'm having trouble seeing what I'm doing wrong...
 
I've created an extension 'getSomething()' for an XMLBeans-derived collection type, and I'm trying to use a bookmark to associate a HashMap object with the collection - but when I create a cursor and set a bookmark, I don't get the bookmark back when I try to get it..  And... I've been unable to find examples anywhere which illustrate a working case...
 
My extension function is currently...
 
  public static String getSomething(XmlObject xo)
  {
    NVPCollection coll = (NVPCollection)xo;
    XmlCursor tmpCursor = coll.newCursor();
    NVPBookmark foo = new NVPBookmark();
    NVPBookmark bmk;
 
    ArrayList fubar = new ArrayList();
 
    bmk = (NVPBookmark)tmpCursor.getBookmark(NVPBookmark.class);
 
    String rval;
 
    if (bmk == null)
    {
    tmpCursor.setBookmark(bmk);
    rval = "created new bookmark:";
    }
    else
    rval = "already had a bookmark:";
 
    tmpCursor.getAllBookmarkRefs(fubar);
 
    tmpCursor.dispose(); // make sure we don't leak...
 
    return rval + String.valueOf(fubar.size());
 
  }
And the bookmark class is just a shell...
 
public class NVPBookmark extends XmlCursor.XmlBookmark
{
  private HashMap nameMap = new HashMap();
 
  public HashMap getMap()
  {
    return nameMap;
  }
}
 

From: Cezar Andrei [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 29, 2006 1:20 PM
To: [email protected]
Subject: RE: XMLBookmark question...

The rule is to call xmlCursor.dispose() after you finished the work with a cursor.

 

Cezar

 

From: Tim Parker [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 28, 2006 4:00 PM
To: [email protected]
Subject: XMLBookmark question...

 

As a follow-on to the HashMap implementation questions...  I feel like I may be missing something but... I'm looking at creating an extension method for my NVPCollection class something like:

 

public String getValueByMap(String keyName)

 

If I hang the hashmap on a bookmark, how do I get the bookmark without having to do a newCursor() every time?  Or is it OK to run newCursor() dozens or hundreds of times without risk of performance or memory problems?  Am I missing something?

 

Tim

 

 

 

From: Cezar Andrei [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 28, 2006 4:33 PM
To: [email protected]
Subject: RE: alternate representations of collections in XMLBeans??

That is a good article to read, also check out the tests under test\cases\xbean\extensions.

 

Cezar

 

From: Tim Parker [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 28, 2006 3:08 PM
To: [email protected]
Subject: RE: alternate representations of collections in XMLBeans??

 

Thank you for the quick reply - I'll look into the XMLBookmark idea...

 

Is there anything else I need to know about the preSet and postSet methods?  I found documentation (including the operationType values) at http://dev2dev.bea.com/pub/a/2004/11/Configuring_XMLBeans.html - is this the latest-and-greatest, or is there a better and/or more current reference available?

 

Tim

 

From: Cezar Andrei [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 28, 2006 2:29 PM
To: [email protected]
Subject: RE: alternate representations of collections in XMLBeans??

Tim,

 

I would recommend using the extensions, otherwise modifying the generated code is definitely possible but missing even a small thing would break the code.

 

Back to using extensions, if one wants to store a state he can do it by using XmlBookmark – which stays with the xml entity even if moved. In your case the hash map should be stored on ‘metadata’ element.

Also the pre/post Set methods are called every time the document is about to change, so you’ll get calls for all creation/modification/deletion events, made through XmlObject interfaces. Modification through other interfaces like XmlCursor or DOM will not trigger the calls to the pre/post Set methods.

 

Cezar

 

From: Tim Parker [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 28, 2006 1:11 PM
To: [email protected]
Subject: alternate representations of collections in XMLBeans??

 

The XMLBeans representation of a collection (for something with a maxOccurs GT 1) is a bit limiting... I'm looking to extend it to look more like a Map interface... and I'm hitting some brick walls...

 

For discussion sake, I'll use a structure with three fields:

 

struct foo

{

    int ID;

    String name;

    HashMap metadata;

}

 

The 'metadata' field contains arbitrary name/value pairs - for simplicity we'll say 'name' and 'value' fields in the hashmap are always strings...

 

The obvious (to me, at least) schema for this is something like:

 

 <xs:complexType name="NVP">
  <xs:sequence>
   <xs:element name="Value" type="xs:string"/>
  </xs:sequence>
  <xs:attribute name="Name" type="xs:string"/>
 </xs:complexType>

 

 <xs:complexType name="NVPCollection">
  <xs:sequence>
   <xs:element name="Entry" type="my:NVP" minOccurs="0" maxOccurs="unbounded"/>
  </xs:sequence>
 </xs:complexType>

 

<xs:complexType name="testCase">

  <xs:sequence>

    <xs:element name="ID" type="xs:int"/>

    <xs:element name="name" type="xs:string"/>

    <xs:element name="metadata" type="my:NVPCollection"/>

  </xs:sequence>

</xs:complexType>

 

====

 

I could build another layer on top of this, but this could get ugly - What I really need is a way to extend NVPCollection so I can address items by name (like in a HashMap) rather than by position... 

 

The ideal would be something like (assuming that we have a mechanism to bind the 'name' field to the map key and the 'value' field to be the one of interest)...

 

NVPCollection thisCollection;

 

// some magic here to get the collection populated...

 

someValue = thisCollection.GetByMap("someArbitraryName");

 

.... Or we could save some binding complexity by doing ...GetByMap("someArbitraryName","value"), saying "get the field 'value' from the collection member whose key field contains 'someArbitraryName'" (The presumption is that the binding to the key field 'name' would need to be established earlier so the map can be maintained)

 

====

 

As I read the documentation, I could build an extension like this, but I'm hosed if I want to do anything more sophisticated than a linear search through the collection on each 'get' call - Unless I'm missing something, I need a place to put an instance-specific HashMap object to maintain mapping between the key field ('name') and the array index... more than a little difficult with the 'static method' requirement for the extension  (Not to mention the population problem for the HashMap object itself, but a preSet or postSet implementation would work as long as I never try to delete anything)..

 

Presumably I could also build an 'extendedNVPCollection' class, based on the NVPCollection class generated by XMLBeans, but how would I wire that back into my (XMLBeans-generated) 'testCase' class?  I don't want to get into creating wrapper classes for every layer...

 

I tried ignoring the "don't touch - generated code" warnings and added some stuff directly to the generated classes for the NVPCollection object, but things started breaking - I'm not sure if the problem is a flaw in my hacking or a fundamental problem I won't solve, so I'm seeking advice - am I tilting at windmills here?

 

Does anyone have ideas as to better ways to do this?

=======================================================

Tim Parker
Senior Developer
PaperThin, Inc.
617-471-4440 x 203
[EMAIL PROTECTED]
www.paperthin.com

===================

PaperThin, Inc. was recently named to KMWorld’s “100 Companies that Matter in Knowledge Management”.

Find out more at www.paperthin.com.

 

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