Eclipse GlassFish HK2 is an implementation of Jakarta Dependency Injection. This project
began as HK2 as an implementation of JSR-330 in a JavaSE environment.
JSR-330 defined services and injection points that can be dynamically discovered at runtime and which allow for Inversion of Control (IoC) and dependency injection (DI). Eclipse Dependency Injection continues to evolve Dependency Injection for Jakarta EE.
GlassFish HK2 provides an API for control over its operation and has the ability to automatically load services into the container.
It is the foundation for the GlassFish V3 and V4 application servers as well as other products.
GlassFish HK2 also has powerful features that can be used to perform tasks such as looking up services or customizing you injections, as well as several extensibility features allowing the users to connect with other container technologies
The following list gives an overview of some of the things that can be customized or extended with GlassFish HK2: