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    <p>Like Tomasz said, you should <strong>never</strong> <em><strong>ever</em></strong> depend on the fact that your application will be used by a small number of clients. The fact that the driver <strong><em>will</em></strong> timeout after a certain amount of time does not guarantee you that you will have enough available connections. Picture this: a lot of databases come pre-configured with a maximum number of connections set to (say) 15 and a timeout of (let's say) 10-15 minutes. If you have 30 clients and each does an operation, somewhere around half-way you'll be stuck short on connections.</p> <p>You should handle connections, files, streams and other resources the following way:</p> <pre><code>public void doSomething() { Connection connection = null; Statement stmt = null; ResultSet rs = null; final String sql = "SELECT ...."); try { connection = getConnection(); stmt = connection.createStatement(); rs = stmt.executeQuery(sql); if (rs.next()) { // Do something here... } } catch (SQLException e) { e.printStackTrace(); } finally { closeResultSet(rs); closeStatement(stmt); closeConnection(connection); } } </code></pre> <p>The try/catch/finally guarantees you that the connection will get closed no matter the outcome. If there is some sort of failure, the finally block will still close the connection, just like it would do, if things were okay.</p> <p>Similarly, with file and streams you need to do the same thing. Initialize the respective object as <code>null</code> outside your try/catch/finally, then follow the approach above.</p> <p>This misconception makes a lot of Java applications misbehave under Windows, where people don't close files (streams to files, etc) and these files become locked, forcing you to either kill the JVM, or even restart your machine.</p> <p>You can also use a connection pool such as for example Apache's DBCP, but even then you should take care of closing your resources, despite the fact that internally, the different connection pool implementations do not necessarily close the connections.</p>
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    1. POJava JDBC efficiency: How long should a connection be maintained?
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    1. COUnderstood. I will add finally clauses wherever there is a connection instance initialized/created, and close it in the finally clause. As for Apache's DBCP, do I need to have Apache running on my Server in order to implement it? Or do I simply need to add some libraries to my Java (front end) project in order for pooling to work? This (http://svn.apache.org/viewvc/commons/proper/dbcp/trunk/doc/PoolingDataSourceExample.java?revision=1143885&view=markup) is what I've noted thus far.
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    2. COSay, would adding commons-pool-1.5.6.jar, commons-dbcp-1.3.jar (JDK 1.4-1.5) or commons-dbcp-1.4 (JDK 1.6+) and j2ee.jar (for the javax.sql classes) in addition to the jbbc.jar driver, to only the front end, be sufficient for pooling to be implemented? Or do I need to make changes to my Server setup? I never got to look at this properly because Glassfish's Admin Console created the pool for you in a matter of clicks.
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    3. COWell, I believe you don't necessarily need to have a web container running in order to use connection pooling. It really depends on the pooling library you'll be using for this. In most application servers there is support for defining data sources. An alternative would be to use something like a Spring / Hibernate setup and add (say) Apache DBCP. I suggest you have a look at a couple of tutorials. It's not really complicated to get it right.
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