Why need for using JDBC write Class.forName(...) for each connection?

Question

If I want to connect to database I should write code like this:

Class.forName("oracle.jdbc.driver.OracleDriver");
Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521/mysidorservicename", "sysdba", "password123");

Why should I load the concrete driver before I connect to database? The result of the Class.forName statement is ignored - the loaded class is obviously not associated with the DriverManager. Can I just load all drivers used for different databases in moment of start application and will not write Class.forName code before each connection?

Answer 1

Older DriverManager implementations (before JDBC 4.0, which was park of JDK 6), required drivers to have a static block that would register them to the DriverManager. Static blocks are called once when the class is loaded by the driver manager. To your question - it doesn't really matter where you load these classes, as long as you load the drivers before attempting to use them.

Since JDBC 4.0 (which is, as mentioned above, a part of JDK 6), you don't have to call Class.forName at all, though. To quote the DriverManager's javadoc:

The DriverManager methods getConnection and getDrivers have been enhanced to support the Java Standard Edition Service Provider mechanism. JDBC 4.0 Drivers must include the file META-INF/services/java.sql.Driver. This file contains the name of the JDBC drivers implementation of java.sql.Driver. For example, to load the my.sql.Driver class, the META-INF/services/java.sql.Driver file would contain the entry [etc..]

In layman's words, it's up to the driver to register itself to declare it provides a JDBC service for a given connection string, and you can just remove the Class.forName calls from your code.