The DefaultHashedDataSourceCluster requires that the user specify an object or a hashCode
which will be used consistantly select a member DataSource form a cluster for each connection
request.
The DefaultIndexedDataSourceCluster requires that the user implement their own method of
selecting which DataSource in the cluster to use for each connection request.
A JDBC connection that has a proxy around it in order to dynamicly implement JDBC2/3 needs
to get a handle to its proxied self so that the proxied version can be returned to the pool.