JDBC Drivers and Class.forName()

The short version: stop using Class.forName(driverClass) to load JDBC drivers. You don't need this, and haven't since Java 6. You arguably never needed this.

This pattern appears all over the internet, and it's wrong.

Backstory

JDBC has more or less always provided two ways to set up Connection objects:

  1. Obtain them from a driver-provided DataSource class, which applications or containers are expected to create for themselves.

  2. Obtain them by passing a URL to DriverManager.

Most people start with the latter, since it's very straightforward to use. However, DriverManager needs to be able to locate Driver subclasses, and the JVM doesn't permit class enumeration at runtime.

In the original JDBC release, Driver subclasses were expected to register themselves on load, similar to

public class ExampleDriver extends Driver {
    static {
        DriverManager.registerDriver(ExampleDriver.class);
    }
}

Obviously, applications can force drivers to load using Class.forName(driverName), but this hasn't ever been the only way to do it. DriverManager also provides a mechanism to load a set of named classes at startup, via the jdbc.drivers system property.

JDBC 4 Fixed That

JDBC 4, which came out with Java 6 in the Year of our Lord Two Thousand and Six, also loads drivers using the service provider system, which requires no intervention at all from deployers or application developers.

You don't need to write any code to load a JDBC 4 driver.

What's The Harm?

It's harmless in the immediate sense: forcing a driver to load immediately before JDBC would load it itself has no additional side effects. However, it's a pretty clear indicator that you've copied someone else's code without thoroughly understanding what it does, which is a bad habit.

But What About My Database?

You don't need to worry about it. All of the following drivers support JDBC 4-style automatic discovery: