Hi Saso,
On 21 Jan 2008, at 13:48, Saso Musevic wrote:
>
> I checked C3P0 source and find out this:
> C3P0 wraps all instances of java.sql.Connection with class
> com.mchange.v2.c3p0.impl.NewProxyConnection
> C3P0 wraps all instances of java.sql.PreparedStatement with class
> com.mchange.v2.c3p0.impl.NewProxyPreparedStatement
> generally, C3P0 wraps all java.sql.* with com.mchange.v2.c3p0.*
> NewProxyConnection returns NewProxyPreparedStatement,
> NewProxyResultSet...
> method "Object NewProxyConnection.rawConnectionOperation(Method,
> Object, Object[])" makes a call to underlying Connection instance
> (in our case that can only be PosgreConnection or OracleConnection,
> in above case it is OracleConnection)
> above method is smart: if you try to make a call to, for example,
> OracleConnection.prepareStatement(String), it checks the return
> type and, in this case, wraps java.sql.PreparedStatement in
> com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.All resources,
> that are acquired this way are not cached/pooled by C3P0 (no
> statement caching/pooling)
>
> Obviously, there is no way to get an instance of OracleConnection
> from it. One option is to wrap NewProxyConnection in a proxy class,
> that implements OracleConnection, delegating all Oracle specific
> calls via NewProxyConnection.rawConnectionOperation.
> I did not do any performance checks, but it sounds like statement
> pooling can give a significant boost, so using C3P0 in spatial apps
> could make sense.
>
> BTW: I still think, that the right way to solve this should be to
> make NewProxyConnection somehow extend OracleConnection.
I've little knowledge of how C3P0 works, so I'm glad you're
investigating this issue. I agree that the current strategy (using
findOracleConnection) can't work with the C3P0 proxy. But I'm not
sure if I entirely understand your proposed solution. Is the
following an accurate description of what you propose?
1. in SDOGeometryType: retrieve the Connection from the
PreparedStatement
2. wrap the connection in a dynamic proxy that implements
OracleConnection
3. in the InvocationHandler of the proxy implement a strategy that
calls the method on the wrapped connection
a) either by locating the OracleConnection (as in the
findOracleConnectio method) and calling the method on that object
b) or by calling rawConnectionOperation (in case the connection is
of type com.mchange.v2.c3p0.NewproxyConnection
If this is an accurate description, then we would keep this approach
general and extensible to other cases where the OracleConnection is
wrapped or proxied. Plus, we should avoid creating compile
dependencies on C3P0 libraries.
Regards,
Karel Maesen
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