MicroSpring A Spring Framework (mainly) compatible IOC container by J.Gibbons, Feb 2005 http://www.tallsoftware.com/microspring/

What is IOC?

• All your classes have default constructors and no other constructors.
• All of your classes are java beans (they have get and set methods), and they never discover anything of the world for themselves. Instead they are handed all knowledge to them through setter functions, just after they are created.
• This is a very simple description, for way more information than the topic deserves read Martin Fowler.

So, if you have a class which uses a datasource, it does not do a lookup through a singleton to locate the datasource. Instead it has a member variable called dataSource (say), and a setter called setDataSource(..). You then set up an xml config file which gives the bean an id, and specify its implementation class, and the fact that it has a property which should be set with another bean called datasource.

Understand? If not, look at the example on the spring documentation page, or micro guide.