在JDBC中使用class.forName

Question

Following is the code to connect to a MySQL database

// This will load the MySQL driver, each DB has its own driver
  Class.forName("com.mysql.jdbc.Driver");
  // Setup the connection with the DB
  connect = DriverManager
      .getConnection("jdbc:mysql://localhost/feedback?"
          + "user=sqluser&password=sqluserpw");

I was learning reflections in java where the class can be obtained using Class.forName()

 Class c = Class.forName("java.awt.Button");

Was the syntax used.

My question is why the MySQL ForName did not needed to be caught in a variable ?

Answer 1

You mean why isn't the Class object saved into a variable. Because it wasn't needed. The class only needed to be loaded, the actual Class object was superfluous.

Also these days you don't even need to do the Class.forName() anymore. The driver will be found from the classpath automatically, if you're using JDBC type 4 (pure java) drivers.

Answer 2

By calling forName() you force the class to be initialized (which is more than just loading it). In that process some static initializers run, which register that particular class with the JDBC manager code in the JDK. That makes a driver instance available internally to the JDK and it is implicitly used in all later code.

Admittedly, relying on unintuitive Reflection calls is a piece of bad design by the authors of JDBC, but in the early days of Java there were less choices than today and the world of Java wasn't as tough. It was a language which had yet to attract serious adoption.