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copied!<p>It's impossible to make an asynchronous call <em>to the database</em> via JDBC, but you can make asynchronous calls <em>to JDBC</em> with <strong>Actors</strong> (e.g., actor makes calls to the DB via JDBC, and sends messages to the third parties, when the calls are over), or, if you like CPS, with <a href="http://en.wikipedia.org/wiki/Futures_and_promises#Promise%20pipelining" rel="noreferrer"><strong>pipelined futures (promises)</strong></a> (a good implementation is <a href="http://code.google.com/p/scalaz/" rel="noreferrer">Scalaz</a> <a href="http://docs.google.com/present/view?id=ddmk3f43_63zpg3jcgz" rel="noreferrer">Promises</a>)</p> <blockquote> <p>I don't consider that using a pool of threads is a solution because it doesn't scale, in the case of heavy concurrent requests this will spawn a very large number of threads.</p> </blockquote> <p>Scala actors by default are event-based (not thread-based) - continuation scheduling allows creating millions of actors on a standard JVM setup. </p> <p>If you're targeting Java, <a href="http://doc.akkasource.org/untyped-actors-java" rel="noreferrer">Akka Framework</a> is an Actor model implementation that has a good API both for Java and Scala.</p> <hr> <p>Aside from that, the synchronous nature of JDBC makes perfect sense to me. The cost of a database session is far higher than the cost of the Java thread being blocked (either in the fore- or background) and waiting for a response. If your queries run for so long that the capabilities of an executor service (or wrapping Actor/fork-join/promise concurrency frameworks) are not enough for you (and you're consuming too many threads) you should first of all think about your database load. Normally the response from a database comes back very fast, and an executor service backed with a fixed thread pool is a good enough solution. If you have too many long-running queries, you should consider upfront (pre-)processing - like nightly recalculation of the data or something like that.</p>

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