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copied!<p>I don't have an environment to test this in, at the moment, however, I <em>believe</em> that you should be closing your Connection, Statement, and ResultSet after each query; if any of these leak, it could leave the Connection hanging in an idle (but not necessarily returned to the pool) state.</p> <p>The Connection object you receive should actually be a sort of proxy from the pooling layer; calling <code>close</code> on it releases your "reservation" on that connection and returns it to the pool. (It will not necessarily close the underlying, actual database connection.)</p> <p>Because it could be remaining open (usually will be), unclosed Statements or ResultSets could be interpreted by the pool layer as an indication of being still “busy.”</p> <p>You may be able to inspect (e.g. debugger makes this easy) the Connection object to identify its state at run-time, to confirm this.</p> <p>For simplicity (…) we used the following nasty little routine in the <code>finally</code> blocks after every database connection call: <code>… finally { closeAll (rs, st, con); }</code>, ensuring that they would fall out of context immediately.</p> <pre><code> /** * Close a bunch of things carefully, ignoring exceptions. The * “things” supported, thus far, are: * <ul> * <li>JDBC ResultSet</li> * <li>JDBC Statement</li> * <li>JDBC Connection</li> * <li>Lock:s</li> * </ul> * <p> * This is mostly meant for “finally” clauses. * * @param things A set of SQL statements, result sets, and database * connections */ public static void closeAll (final Object... things) { for (final Object thing : things) { if (null != thing) { try { if (thing instanceof ResultSet) { try { ((ResultSet) thing).close (); } catch (final SQLException e) { /* No Op */ } } if (thing instanceof Statement) { try { ((Statement) thing).close (); } catch (final SQLException e) { /* No Op */ } } if (thing instanceof Connection) { try { ((Connection) thing).close (); } catch (final SQLException e) { /* No Op */ } } if (thing instanceof Lock) { try { ((Lock) thing).unlock (); } catch (final IllegalMonitorStateException e) { /* No Op */ } } } catch (final RuntimeException e) { /* No Op */ } } } } </code></pre> <p>This was just syntactic sugar to ensure that nobody forgot to put in the longer, uglier stanza of <code>if (null != con) { try { con.close () } catch (SQLException e) {} }</code> (usually repeated three times for ResultSet, Statement, and Connection); and removed the "visual noise" of what our formatter would turn into a full screen of incidental cleanup code on every block of code that touched the database.</p> <p>(The <code>Lock</code> support in there was for some related, but nasty, deadlock states on potential exceptions, that didn't have much to do with the database at all, but we used in a similar way to reduce the line noise in some thread-synchronization code. This is from an MMO server that might have 4,000 active threads at a time trying to manipulate game objects and SQL tables.)</p>

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