Why Do Some Java JDBC Applications Work Without Explicit Driver Registration Using `Class.forName()`?

JDBC Driver Registration in Java: Clarifying the Need for Class.forName(JDBC_DRIVER)

It has been reported that Java version 6 and beyond eliminates the requirement for registering JDBC drivers using the Class.forName(JDBC_DRIVER) method due to the utilization of the "jdbc.drivers" system property. However, some developers have encountered a scenario where retrieving the value of "jdbc.drivers" returns null.

This discrepancy prompts the question: why does Java applications using JDBC work correctly despite the absence of an explicitly registered driver?

The answer lies in a feature introduced in Java 6 and JDBC 4 known as "service providers." This mechanism allows the JVM to detect implementations of specified interfaces during startup. JDBC drivers conforming to this concept can be automatically registered by the DriverManager, effectively eliminating the need for Class.forName().

The service registration process relies on the presence of a "services" directory within the driver's JAR file in the META-INF directory. This directory must contain a text file naming the implemented interface (java.sql.Driver for JDBC drivers) and the corresponding implementing class.

By adhering to the service provider concept, JDBC drivers can be registered automatically, eliminating the need for explicit Class.forName() calls. However, this only applies to drivers compatible with the service provider mechanism.

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