The Bean's life cycle

Bean life cycle

Bean's life cycle is generally divided into 4 stages

Instantation---->Property assignment Populate---->Initialization---->Destruction Destriction

In these 4 stages, it is divided into several small steps, let's go into detail below

First step (instantiating the bean)

There are two cases here. If the BeanFactory container is used, when an uninitialized bean is requested from the container, or an uninitialized dependency needs to be injected into the dependency, the container will call createBean for instantiation

For using the ApplicationContext container, when the container is started, all beans are instantiated by obtaining the information in the BeanDefinition object

Part 2(set to detailed properties)

The instantiated object is encapsulated in the BeanWrapper object, and then Spring will complete the property setting and dependency injection according to the information in the BeanDefinition and the interface for setting properties provided by the BeanWrapper

Step 3 (handling the Aware interface)

Spring will detect whether the object implements the lxxxAware interface. Through the Aware type interface, we can get some resources of the Spring container

This is divided into the following situations

If the bean implements the BeanNameAware interface, the setBeanName(String beanld) method it implements will be called, and the name of the bean is passed in

If the Bean implements the BeanClassLoaderAware interface, call the setBeanCLassLoader() method and pass in the ClassLoader object instance

If the Bean implements the BeanFactoryAware interface, it will be called to implement the setBeanFactory() method, and the Spring factory itself will be passed

If this bean implements the ApplicationContextAware interface, the setApplicationContext(ApplicationContext) method will be called and the Spring context will be passed in

Step 4(BeanPostProcessor preprocessing)

If some custom preprocessing is performed on the bean, then the bean can implement the BeanPostProcessor interface, then the PostProcessorBeaforeInitialization(Object obj,String s) method will be called

Step 5(InitializingBean)

If you implement the InitializingBean interface, you only want the afterPropertiesSet() method

Step 6(init-method)

If the bean is configured with the init-method attribute in the Spring configuration file, its configured initialization method will be called automatically

The seventh step BeanPostProcessor post-processing

After the above steps, the bean has been created correctly, and the bean can be used after that

If the bean implements the BeanPostProccessor interface, the postProccessAfterInitialization(object obj, String s) method will be called; since this method is called at the end of bean initialization, it can be applied to memory or caching techniques

Step 8DisposableBean

When the bean is not needed, it will go through the cleanup phase. If the bean implements the DisposableBean interface, it will call the Destroy() method of other implementations

Step 9destory-method

Finally, if the destruction-method attribute is configured in the Spring configuration of this Bea, its configured destruction method will be called automatically