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From David Van Couvering <da...@vancouvering.com>
Subject Re: Derby storage using Java Web Start PersistenceService API - is it doable?
Date Mon, 19 Mar 2007 17:29:35 GMT
I also want to emphasize that if you choose to try and do this, you 
should feel very free to ask for help and guidance on the derby-dev 
list.  The dev team is very responsive and helpful, in my experience.


Daniel John Debrunner wrote:
> David Van Couvering wrote:
>> Hi, Luigi.  I looked at this once, and it really didn't seem that the 
>> API provided by the JWS persistence service was sufficient for the 
>> needs of Derby.  But I didn't look too closely at it.  For me demo 
>> needs, a popup was fine.
>> What you'd have to do is provide a new implementation of the storage 
>> interface.  Others on this list can give you better guidance than I 
>> about where to look and how to do this.  I suspect this is not for the 
>> faint of heart...
> As Andrew pointed out this is would be an implementation of 
> org.apache.derby.io.StorageFactory against Java Web Start 
> PersistenceService API.
> The StorageFactory is is an abstraction around the java filesystem 
> classes so in theory it's not hard to understand. All of the database 
> specific internals are above this layer and would not need to be 
> changed. It's much like the Directory abstraction in Apache Lucene Java.
> You can find the internals java doc at
> http://db.apache.org/derby/javadoc/engine/
> then look for the org.apache.derby.io package.
> Here's some information on getting involved in Derby's development:
>  http://wiki.apache.org/db-derby/DerbyDev
> I would encourage you to subscribe to derby-dev and involve the 
> development community in implementing this (asking questions, 
> incremental development etc.).
> The in-memory implementation Andrew references may not be the best model 
> to follow, the implementation seems to add new api classes with no 
> indication of what their functionality is required to be, i.e. no 
> comments. Then the original contributor never responded to any questions 
> and non-one else has had the itch to pick up the code. Thus that 
> implementation has stalled and not been committed. It would be a shame 
> for any Java Web Start PersistenceService implementation to go the same 
> way.
> In the Derby code there are three implementations of StorageFactory that 
> are in use, for file system, jar files and classpath. There is one more 
> that is not in use, fetching data from an http server. Look for 
> subclasses of StorageFactory.
> HTH,
> Dan.

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