What is kernel?

Kernel is an instance of the Kernel class which is responsible for managing scope and visibility of beans. Kernel handles bean:

  • registration of a bean
  • unregistration of a bean
  • initialization of a bean
  • deinitialization of a bean
  • dependency injection to the bean
  • handling of bean lifecycle
  • registration of additional beans based on annotations (optionally using registered class implementing BeanConfigurator as defaultBeanConfigurator)
  • configuration of a bean (optionally thru registered class implementing BeanConfigurator as defaultBeanConfigurator)

Kernel core is responsible for dependency resolution and maintaining lifecycle of beans. Other features, like proper configuration of beans are done by additional beans working inside the Kernel.

Kernel identifies beans by their name, so each kernel may have only one bean named abc. If more than one bean has the same name, then the last one registered will be used as its registration will override previously registered beans. You may use whatever name you want to name a bean inside kernel but it cannot:

  • be service as this name is used by Tigase Kernel internally when `RegistrarBean`s are in use (see RegistrarBean
  • end with #KERNEL as this names are also used by Tigase Kernel internally


Kernel initializes beans using lazy initialization. This means that if a bean is not required by any other beans, or not retrieved from the kernel manually, an instance will not be created.

During registration of a bean, the kernel checks if there is any beans which requires this newly registered bean and if so, then instance of a newly registered bean will be created and injected to fields which require it.