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From Craig L Russell <Craig.Russ...@Sun.COM>
Subject Re: Proposal to change Derby's public api for XADataSource and ConnectionPoolDataSource
Date Wed, 17 May 2006 00:24:20 GMT
Hi,

It appears that you have made the appropriate change.

XADataSource is not a user API, and in fact isn't a kind-of  
DataSource. It was misnamed (IMHO) from the beginning. An  
XADataSource is a factory that produces XAConnections, which are not  
Connections, but are chimeras (produced by an internal mating of an  
XAResource and a Connection). You might want to see if Derby's  
implementation also incorrectly has XAConnection extending Connection.

Craig

On May 11, 2006, at 1:09 PM, Rick Hillegas wrote:

> Dear Derby users,
>
> Please read this message if you work on an application server or in  
> an application layer which cares about distributed transactions and/ 
> or pooled connections.
>
> Right now the inheritance graph for Derby's DataSources does not  
> mirror the corresponding graph of interfaces in javax.sql. Derby's  
> DataSources are classes which you will find in Derby's published  
> javadoc for the package org.apache.derby.jdbc. In particular,  
> Derby's XADataSources and ConnectionPoolDataSources implement the  
> DataSource interface. This is so even though the  
> javax.sql.XADataSource and javax.sql.ConnectionPoolDataSource  
> interfaces themselves do not extend javax.sql.DataSource.
>
> We believe this is confusing, particularly to developers who are  
> trying to build applications which easily port across different  
> vendors' JDBC implementations. We propose to rework the hierarchy  
> of classes in org.apache.derby.jdbc so that our XADataSources and  
> ConnectionPoolDataSources no longer implement javax.sql.DataSource.  
> We propose to expose this change in Derby 10.2.
>
> However, we do not want to make this change if it will break  
> existing applications. Please let us know if you think this will  
> break your app server or other Derby-powered application.
>
> Thanks,
> -Rick
>
>
> ---------------------------------------------------------------------- 
> -------------
>
> Here is a bit more detail on the problem. This is the inheritance  
> graph from javax.sql:
>
>                     CommonDataSource
>                       /          |           \                  
> XADataSource DataSource ConnectionPoolDataSource
>
> Here is the corresponding 10.1 graph from org.apache.derby.jdbc:
>
>                    ClientDataSource
>                           /           \
> ClientXADataSource    ClientConnectionPoolDataSource
>
> We propose the following 10.2 graph for org.apache.derby.jdbc
>
>                             ClientBaseDataSource
>                              /               |                \
> ClientXADataSource ClientDataSource ClientConnectionPoolDataSource
>

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!


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