One of the most important specifications in the Java EE platform is Contexts and Dependency Injection (CDI). As stated on the cdi-spec.org site, it is a suite of complementary services that can improve the overall structure and design of code. The specification provides the following features for Java EE and Java SE applications, as per the cdi-spec.org:
Contextual objects with a well-defined lifecycle providing multiple scopes of availability
Ability to bind directly between contextual objects and Unified Expression Language (EL)
Dependency injection utilizing a type-safe system ...
