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:

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

+
PostgreSQL (since version 8.0-321, in 2007)
+
+
Firebird (since version 2.2, in 2009)
+
+
MySQL (since version 5.0, in 2005)
+
+
H2 (since day 1, as far as I can tell)
+
+
Derby/JavaDB (since version 10.2.1.6, in 2006)
+
+
SQL Server (version unknown, because MSDN is archaeologically hostile)
+

+ + + +

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+ + + + + +

JDBC Drivers and Class.forName()

Backstory

JDBC 4 Fixed That

What's The Harm?

But What About My Database?

JDBC Drivers and `Class.forName()`