Using Class.forName() in Java

[Jeremy McNally]

Can someone please explain to me what the below line of code is doing. I understand that by calling Class.forName(we are initializing everything that is static in that class). I may be a little off saying that but I still don't get the general's of it. Also the exact example below.

Details are great! Thanks to anyone that is willing to give some detailed input on this.

Class.forName("oracle.jdbc.driver.OracleDriver");

[Jesper de Jong]

It dynamically loads the class oracle.jdbc.driver.OracleDriver, which is a JDBC driver for the Oracle database.

Java's database access API, JDBC, is set up in such a way that you (mostly) don't have to worry what exact database you are using when you write your program. Vendors of different databases provide drivers to do the database-specific things that are necessary when you want to use a database. It used to be the case that you needed to initialize the driver with a Class.forName(...), so that JDBC knew that this driver was available.

However, since JDBC version 4.0 it is no longer necessary to do this explicitly - JDBC can now discover drivers by itself.

So, if you are not using a really old version of Java or a really old database driver, you can just leave this line of code out - it is not necessary.

[Jeremy McNally]

Thank you for your response. That cleared my example up for me.
Generally though, would I want to use Class.forName() in any other case?

[Paul Clapham]

Yes, there are other cases where you might want to load a class whose name you know. In those cases, usually the class is going to implement an interface which your code already knows about. This kind of architecture is often called "plugin" as you're taking a class which you have written and plugging it in to some code which just wants an implementation of some interface.

[Jeremy McNally]

Based off of your response, I put an example together. In this scenario, how would the Class.forName() be used. (if it would be at all in this case). I'm just trying to understand this and the exact case it would be used. You did great explaining it but I'm still lost in terms of the benefit and when I'd use it. Thank you.

With a base example, give or take what is actually listed in my sample below, when would I use Class.forName()?

public interface Dao {
method1();
}

public class DaoImpl implements Dao {
implement method 1...
}

Configuration
<bean id="dao" class="com.example.daoImpl" />

public class ServiceClass{
@Autowired 
Dao dao; 


}

[Campbell Ritchie]

Too complicated a question for “Beginning”: moving discussion.