Spring Bean Life Cycle

• When the class is created we can see there are 'Aware' interfaces that get inialized
  • BeanNameAware
  • BeanFactoryAware
  • ApplicationContextAware

Shutdown

Container Shutdown -> Disponable Bean's destroy() -> Call custom destroy method -> Terminated

Callback Interfaces

• Spring has two interfaces you can implement for call back events
• InitializingBean.afterPropertiesSet()
  • called after properties are set
• DisposableBean.destroy()
  • called during bean destruction in shutdown

Life Cycle Annotations

• Spring has two annotations you can use to hook into the bean life cycle
• @PostConstruct
  • called after the bean has been constructed but before its returned to the requesting object
• @PreDestroy
  • called just before the bean is destroyed by the container

Bean Post Processors

• Gives you a means to tap into the Spring context life cycle and interact with beans as they are processed
• Implement interface BeanPostProcessor
• postProcessBeforeInitialization
  • called before bean initialization method
• postProcessAfterInitialization
  • called after bean initialization

Note: The guru admits in all his years he has never used these

'Aware' Interfaces

• Spring has over 14 Aware Interfaces
• These are used to accses the Spring Framework infrastructure
• Rarely used by Devs, mostly used within the framework itself The more useful ones:
• ApplicationEventPublisherAware - used for creating custom events inside spring and set up event listeners
• BeanFactoryAware - If you need to handle a bean within a process

Spring Bean Scopes

• Singleton (default) - Only one instance of the bean is created in the IoC container
• Prototype - A new instance is created each time the bean is requested
• Request - Single instance per http request.*
• Session - Single instance per http session.*
• Global-session - A single instance per global session. Typically only used in a Portlet context.*
• Application - bean is scoped to the lifecycle of a ServletContext.*
• Websocket - Scopes a single bean definition to the lifecycle of a WebSocket.*
• Custom scope - extensible, define your own "Scope" interface. See docs for details

*Only valid in the contex of a web-aware Spring ApplicationContext

No declaration is needed for singleton scope.

In Java configuration use the @Scope annotation. We see the xml configuaration above.