CODEWITHSUNDEEP
jdbcconnection-poolingc3p0
MADDY987
MADDY987

Reputation: 33

Connection.close() on C3P0NativeJdbcExtractor closes the connection and removes it from the Pool

I am using C3P0NativeJdbcExtractor to extract the native JDBC connection as below. 

public Connection getNativeConnection() throws SQLException{
        C3P0NativeJdbcExtractor nativeJbdc;
        nativeJbdc = new C3P0NativeJdbcExtractor();
        return nativeJbdc.getNativeConnection(dataSource.getConnection());
    }

Note that the data source here is obtained of a C3P0 Connection Pool. When I do a Connection.close() returned on this method, it is actually closing the connection instead of returning to the pool.

However if we close the unwrapped connection, then it is returned to the Pool.

Is there is a reason to why closing the wrapped connection here is failing to return the connection to the pool?

Upvotes: 1

Views: 464

Answers (1)

Mark Rotteveel
Mark Rotteveel

Reputation: 109000

A connection pool like c3p0, holds a collection of physical ('native') connections created by a JDBC driver. When you ask it for a connection, it wraps that physical connection in a proxy, also known as the logical connection.

That proxy will intercept certain methods like Connection.close(). For close() instead of closing the connection, it invalidates the logical connection so it behaves as a closed connection, and it returns the physical connection to the connection pool.

Your code extracts the physical connection from the logical connection, and returns that instead, so if you call close() on that, you actually close the connection to the database instead of returning it to the pool.

You should almost never have a reason to extract the native connection like that. The only reason is when you need access to driver-specific features. You should try to use standard JDBC as much as possible, and only unwrap to access driver-specific features when you really need to.

When you call close(), make sure you call close() on the logical connection that you received from the connection pool, not on the unwrapped physical connection.

Upvotes: 4

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