So it seems the only way to actually guarantee that one’s ResultSets, Statements and Connections get closed is by closing them yourself.

I’m happy now, thanks.

Actually closing connections in large enough systems isn’t that common, especially with database pooling. Connections can be used for a lot of transactions, and the statements/resultsets use resources while the connection is open. Also, not all statements return result sets, such as statement.executeUpdate(), so you have to close it explicitly.

The general rule of thumb for JDBC development is explicitly close a resource (often through a finally block) as soon as it is not needed, or at least before the code does any other time consuming work such as calling other resources/connections. Many JDBC performance problems are caused by developers forgetting to close resources properly.

Perhaps, if every connection had exactly one statement and every statement had exactly one result set, your argument would make sense, but in practice this is not the case. In particular, such a system would not support transactions since the connection would be closed between any two calls.

One other question: Why would should we bother calling rs.close and stmt.close, when con.close is defined to automatically close those resources for us?

http://java.sun.com/j2se/1.4.2/docs/api/java/sql/Connection.html#close%28%29
> Releases this Connection object’s database and JDBC resources immediately instead of waiting for them to be automatically released.

In fact, looking at this JavaDoc, it seems that Sun’s intention is for developers to rely on connections being closed during garbage collection, and that calling close() is only required for special cases.

You make the mistaken assumption that you can predict what the garbage collector is going to do. In fact, the garbage collector isn’t likely to run until the system is close to running out of memory. If you never close any DB resources, you will run out of connections before you run out of memory. Also, keep in mind the garbage collector doesn’t have to run, nothing about the behavior is guaranteed and its far from the garbage collectors job to manage database resources.

http://java.sun.com/j2se/1.4.2/docs/api/java/sql/ResultSet.html#close%28%29
http://java.sun.com/j2se/1.4.2/docs/api/java/sql/Statement.html#close%28%29
http://java.sun.com/j2se/1.4.2/docs/api/java/sql/Connection.html#close%28%29

http://commons.apache.org/dbutils/

Melloware
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