The views expressed on this blog are my own and do not necessarily reflect the views of Oracle.

Monday, June 2, 2008

Life cycle of a bean in spring

Spring's bean has a very elaborated life cycle which gives opportunities to hook up some custom code or logic in various life cycle stages. There are two distinct spring containers one is bean factory and another is application context. Life cycle phases varies a lil in the containers. More precisely, only one additional phase is added in case of application context. Let's see what these phases are:

1. Instantiate: in this phase container finds the bean's definition and instantiates it.
2. Populate properties: in this phase using the dependency injection all the properties are populated which are specified in the bean definiton (in the xml file).
3. BeanNameAware: If BeanNameAware interface is implemented the factory calls the setBeanName() passing the Bean's Id.
4. BeanFactoryAware: if BeanFactoryAware interface is implemented setBeanFactory() method is called.
5. ApplicationContextAware: This step is valid only if the Application context container is used. In this phase if bean implements the ApplicationcontextAware then setApplicationContext() method is called.
6. Pre-initialization: If any BeanPostProcessors are associated with the bean then their postProcessBeforeInitialization() methods will be called.
7. InitializingBean: If an init-methodis specified for the bean then it is called.
8. Call custom init-method: If there are any BeanPostProcessors are associated then postProcessAfterInitialization() is called.

Above are the lifecycle phase when a bean becomes ready to use in the container. An existing bean can be removed from the container in two ways:
1. DisposableBean: If bean implements the DisposableBean interface then destroy() method is called.
2. Call-custom destroy: if custom-destroy method is specified then it is called.

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