This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
I have a little doubt about Tomcat Connection Pool using jndi/dbcp:
When I do something like it:
why I always need to close the current Connection? I was think that if I do it the connection will be closed, but I realize that it returns to the pool, right? How does it function? I call a method to close a connection and instead close it, it return to the pool.
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Well, polymorphism (dynamic method invocation) could be your answer. When you call ds.getConnection() you get an object that implements the Connection interface. What actually happens within the close() method of that implementation is up to the concrete implementation. I've not used DBCP or Tomcat connection pooling. Are you sure that what you're saying is correct?
Personally I would prefer to see a PooledConnection.release() or a DBConnectionPool.returnConnection(con) method, which would help to prevent such confusion as you're experiencing.
The close() method on a Connection retrieved from a pool releases that connection back to the pool. A close() on a non-pool connection does whatever the driver implementors felt necessary. Regardless, it's always wise to formally terminate communications, and not only on Connections. Statements should be closed as well. Normally I don't explicitly close ResultSets, since they will (per documentation) close their resultsets, but for a long-term holding, it's handy to know I can.
The best place to close Statements and Connections is in a "finally" clause. Otherwise thrown exceptions may cause resources to leak.
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