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    <p>Yes, you should consider re-using connections rather than creating a new one each time. The usual procedure is:</p> <ul> <li>make some guess as to how many simultaneous connections your database can sensibly handle (e.g. start with 2 or 3 per CPU on the database machine until you find out that this is too few or too many-- it'll tend to depend on how disk-bound your queries are)</li> <li>create a <strong>pool</strong> of this many connections: essentially a class that you can ask for "the next free connection" at the beginning of each method and then "pass back" to the pool at the end of each method</li> <li>your getFreeConnection() method needs to return a free connection if one is available, else either (1) create a new one, up to the maximum number of connections you've decided to permit, or (2) if the maximum are already created, wait for one to become free</li> <li>I'd recommend the Semaphore class to manage the connections; I actually have a short article on my web site on <a href="http://www.javamex.com/tutorials/synchronization_concurrency_semaphore2.shtml" rel="noreferrer">managing a resource pool with a Semaphore</a> with an example I think you could adapt to your purpose</li> </ul> <p>A couple of practical considerations:</p> <ul> <li>For optimum performance, you need to be careful <strong>not to "hog" a connection while you're not actually using it to run a query</strong>. If you take a connection from the pool once and then pass it to various methods, you need to make sure you're not accidentally doing this.</li> <li>Don't forget to return your connections to the pool! (try/finally is your friend here...)</li> <li>On many systems, you <strong>can't keep connections open 'forever'</strong>: the O/S will close them after some maximum time. So in your 'return a connection to the pool' method, you'll need to think about <strong>'retiring' connections that have been around for a long time</strong> (build in some mechanism for remembering, e.g. by having a <strong>wrapper object</strong> around an actual JDBC Connection object that you can use to store metrics such as this)</li> <li>You may want to consider using prepared statements.</li> <li>Over time, you'll probably need to <strong>tweak the connection pool size</strong></li> </ul>
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    1. POHow many JDBC connections in Java?
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    1. USNeil Coffey
    1. USNeil Coffey
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    1. POHow many JDBC connections in Java?
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    1. COCould you elaborate how Prepared Statements could help here?
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    2. CO@neilCoffey if 'retiring' of connections is not considered; Why do we need of multiple connections? one single connection can be used everywhere rit; since statement objs are always different? When we requires multiple connection in the application?
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      1. USKanagavelu Sugumar
    3. COOne single connection be used to run a (theoretically) infinite number of queries as you say. But it can only run one query at a time. On a moderately complex system, you generally need to allow for the possibility of running several queries concurrently.
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