java - MySQL JDBC 插件加载

Question

我在初始化 MySQL JDBC 连接的代码中看到过很多这种类型的代码。

Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://10.0.0.2:3306", "username", "password");

现在我的问题是为什么/什么时候需要第一行？通过这个，我已经能够毫无问题地连接到 MySQL 数据库:

conn = DriverManager.getConnection("jdbc:mysql://10.0.0.2:3306", "username", "password");

我正在使用 Java 7 和 Connector/J 5.0.8 驱动程序。

我的代码中没有任何直接加载 MySQL 驱动程序的导入或类加载语句，只有通用 Java SQL 接口(interface)类。

Answer 1

简答:使用 4.0 之前的 JDBC 驱动程序(JDBC 4.0 引入了 JDBC 驱动程序类的自动加载)

In previous versions of JDBC, to obtain a connection, you first had to initialize your JDBC driver by calling the method Class.forName. This methods required an object of type java.sql.Driver. Each JDBC driver contains one or more classes that implements the interface java.sql.Driver. The drivers for Java DB are org.apache.derby.jdbc.EmbeddedDriver and org.apache.derby.jdbc.ClientDriver, and the one for MySQL Connector/J is com.mysql.jdbc.Driver. See the documentation of your DBMS driver to obtain the name of the class that implements the interface java.sql.Driver.

Any JDBC 4.0 drivers that are found in your class path are automatically loaded. (However, you must manually load any drivers prior to JDBC 4.0 with the method Class.forName.)

来源:JDBC Basics