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Summary of the core steps in the life cycle of beans

2022-07-01 18:55:00 【51CTO】

BFPP And BPP explain

The following text is for convenience , use BFPP Generation refers to BeanFactoryPostProcessor, use BPP Generation refers to BeanPostProcessor.

xml/ Annotation mode on spring

      
      
       
       
// xml The way 
       
       
ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-test.xml");
       
       
//  Annotation mode 
       
       
AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext("com.hulang.bean");
      
      
      
      
       
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       5.

Container to create

refresh() Medium obtainFreshBeanFactory()

Create a container

Created is DefaultListableBeanFactory

       
       DefaultListableBeanFactory 
       
       beanFactory 
       
       = 
       
       createBeanFactory();
      
1.

Set container attribute values

       
       beanFactory.
       
       setSerializationId(
       
       getId());
       
       customizeBeanFactory(
       
       beanFactory);
      
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load bean Defining information

      
      
       
       loadBeanDefinitions(beanFactory);
      
      
      
      
       
       1.

Contains many overloaded methods with duplicate names , Suggest debug Debug view , Otherwise, it's easy to faint .

xlm convert to document

document It can be interpreted as element

parseDefaultElement(ele, delegate)

The default refers to bean

delegate.parseCustomElement(ele)

Customized refers to context、aop Wait for the beginning or customized label .

The results of the parsing of the above two tags are encapsulated in BeanDefinition in , What you get is GenericBeanDefinition, The subsequent instantiation uses RootBeanDefinition, A merge is needed .

Set attribute values for the container factory

prepareBeanFactory(beanFactory);

Set class loader, etc

postProcessBeanFactory

Empty method , For subclasses to implement .

Instantiate and execute BFPP

      
      
       
       invokeBeanFactoryPostProcessors(beanFactory)
      
      
      
      
       
       1.

Call and execute BFPP, The object of operation is BeanFactory, You can create 、 Modify or introduce others BeanDefinition, There is a very important class ,ConfigurationClassPostProcessor

ConfigurationClassPostProcessor

complete @Bean,@[email protected],@Import,@ImportSource And so on

complete BPP Instantiation and registration of

registerBeanPostProcessors(beanFactory), complete BPP Registration and instantiation of , Convenient for subsequent creation bean After the procedure is completed, call before/after Method heap bean enhanced .

Complete the creation of custom objects

finishBeanFactoryInitialization(beanFactory)

List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

Put the object to be created into list in , Create one by one .

getMergedLocalBeanDefinition The above mentioned GenericBeanDefinition convert to RootBeanDefinition

       
       for (
       
       String 
       
       beanName : 
       
       beanNames) {
       
       RootBeanDefinition 
       
       bd 
       
       = 
       
       getMergedLocalBeanDefinition(
       
       beanName);
       
       if (
       
       !
       
       bd.
       
       isAbstract() 
       
       && 
       
       bd.
       
       isSingleton() 
       
       && 
       
       !
       
       bd.
       
       isLazyInit()) {
       
       if (
       
       isFactoryBean(
       
       beanName)) {
       
       Object 
       
       bean 
       
       = 
       
       getBean(
       
       FACTORY_BEAN_PREFIX 
       
       + 
       
       beanName);
       
       if (
       
       bean 
       
       instanceof 
       
       SmartFactoryBean
       
       <?> 
       
       smartFactoryBean 
       
       && 
       
       smartFactoryBean.
       
       isEagerInit()) {
       
       getBean(
       
       beanName);
       
          }
       
        }
       
       else {
       
       getBean(
       
       beanName);
       
        }
       
      }
       
    }
      
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getBean

doGetBean

First look in the container , If there is no more creation

createBean

doCreataBean

createBeanInstance

establish bean There are multiple ways

getInstanceSupplier(Supplier Way to create )

instantiateUsingFactoryMethod(FactoryMethod Way to create )

instantiateBean( default , Create by reflection )

instantiateBean

There's actually another one BPP Proxy mode creates objects , But not in createBeanInstance, But in the previous steps

Finally, reflection is called bean The creation of

Register the lifecycle interface

That is to say applyMergedBeanDefinitionPostProcessors

       
       // Allow post-processors to modify the merged bean definition.
       
       synchronized (
       
       mbd.
       
       postProcessingLock) {
       
       if (
       
       !
       
       mbd.
       
       postProcessed) {
       
       try {
       
       applyMergedBeanDefinitionPostProcessors(
       
       mbd, 
       
       beanType, 
       
       beanName);
       
        } 
       
       catch (
       
       Throwable 
       
       ex) {
       
       throw 
       
       new 
       
       BeanCreationException(
       
       mbd.
       
       getResourceDescription(), 
       
       beanName,
       
       "Post-processing of merged bean definition failed", 
       
       ex);
       
        }
       
       mbd.
       
       postProcessed 
       
       = 
       
       true;
       
      }
       
    }
      
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Finish this step @PostConstruct、@PreDestory、@Resource、@Autowire、@Value Annotation parsing work .

Fill properties populateBean

Create dependent objects , The circular dependency problem is triggered again

To initialize initializeBean

perform invokeAwareMethods

  
       private 
       
       void 
       
       invokeAwareMethods(
       
       String 
       
       beanName, 
       
       Object 
       
       bean) {
       
       if (
       
       bean 
       
       instanceof 
       
       Aware) {
       
       if (
       
       bean 
       
       instanceof 
       
       BeanNameAware) {
       
        ((
       
       BeanNameAware) 
       
       bean).
       
       setBeanName(
       
       beanName);
       
      }
       
       if (
       
       bean 
       
       instanceof 
       
       BeanClassLoaderAware) {
       
       ClassLoader 
       
       bcl 
       
       = 
       
       getBeanClassLoader();
       
       if (
       
       bcl 
       
       != 
       
       null) {
       
          ((
       
       BeanClassLoaderAware) 
       
       bean).
       
       setBeanClassLoader(
       
       bcl);
       
        }
       
      }
       
       if (
       
       bean 
       
       instanceof 
       
       BeanFactoryAware) {
       
        ((
       
       BeanFactoryAware) 
       
       bean).
       
       setBeanFactory(
       
       AbstractAutowireCapableBeanFactory.
       
       this);
       
      }
       
    }
       
  }
       
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