Contexts and Dependency Injection (CDI ) JSR 299 is a new feature in Java EE 6 Web Profile .  Its Enhance the JSR 330 Dependency Injection in Java. CDI are highly used annotation. CDI makes Loose coupling between classes. To use javax.inject.Inject annotation, we can inject any class into another classes 

i put 4 part series of CDI, you can get it here