Spring源码-Bean的生命周期

Spring容器中一个bean的生命周期如下：

Bean初始化前

BeanFactoryPostProcessor–>postProcessBeanFactory方法：针对的是BeanFactroy，在BeanFactroy的refresh方法中的invokeBeanFactoryPostProcessors中这一步。

作用：可以获取BeanDefiniton并且赋予一些属性初始值。

Bean初始化过程

构造方法

BeanNameAware–>setBeanName方法:实现BeanNameAware接口，将BeanName传给Bean，在initializeBean过程中调用
作用：Bean可以获取BeanName

ApplicationContextAware–>setApplicationContext方法:实现ApplicationContextAware接口，将ApplicationContext传给Bean，在prepareBeanFactory过程中将ApplicationContextAwareProcessor加到beanFactory，在initializeBean方法中调用postProcessBeforeInitialization
作用：Bean可以获取ApplicationContext

BeanPostProcessor–>postProcessBeforeInitialization方法：不同于BeanFactoryPostProcessor的是，这里针对的是Bean对象本身，在initializeBean方法中的applyBeanPostProcessorsBeforeInitialization方法调用
作用：针对特定的bean可以修改bean的属性等

@PostConstruct方法：通过注解@PostConstruct执行的方法，在构造函数后面执行。

InitializingBean–>afterPropertiesSet方法：实现InitializingBean接口，在initializeBean方法中调用

BeanPostProcessor–>postProcessAfterInitialization方法：初始化Bean之后执行

DisposableBean–>destroy方法：bean的销毁方法，在容器被销毁时候回被调用
作用：执行bean的清理工作等。

演示代码如下，请分别创建如下的文件。自行修改basePackages

//测试类
@Component
public class TestObjImpl implements InitializingBean, DisposableBean, BeanNameAware, ApplicationContextAware {

  private String beanName="";
  private ApplicationContext applicationContext;

  @Autowired
  private TestObjImplWithOutAnnoation testObjImplWithOutAnnoation;


  public TestObjImpl() {
    System.out.println("构造方法");
  }

  @PostConstruct
  public void init() {
    System.out.println("@PostConstruct方法");
  }

  @Override
  public void setBeanName(String name) {
    System.out.println("BeanNameAware-->setBeanName 方法");
    this.beanName = name;
  }

  @Override
  public void afterPropertiesSet() throws Exception {
    System.out.println("InitializingBean-->afterPropertiesSet 方法");
  }

  @Override
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    System.out.println("ApplicationContextAware-->setApplicationContext  方法");
    this.applicationContext=applicationContext;
  }

  @Override
  public void destroy() throws Exception {
    System.out.println("DisposableBean-->destroy 方法");
  }

  @Override
  public void hello() {
    System.out.println(beanName+" say hello");
  }
}

//BeanPostProcessor
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
  @Override
  public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    if (bean instanceof TestObjImpl) {
      System.out.println("BeanPostProcessor-->postProcessBeforeInitialization==="+beanName);
    }
    return bean;
  }

  @Override
  public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    if (bean instanceof TestObjImpl) {
      System.out.println("BeanPostProcessor-->postProcessAfterInitialization ==="+beanName);
    }
    return bean;
  }
}

//BeanFactoryPostProcessor
@Component
public class TestBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
  @Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    System.out.println("BeanFactoryPostProcessor-->postProcessBeanFactory 方法");
  }
}


//main
public class Starter {

  public static void main(String[] args) {
    AnnotationConfigApplicationContext applicationContext= new AnnotationConfigApplicationContext("basePackages 需要自行修改");
    TestObj obj=applicationContext.getBean(TestObj.class);
    obj.hello();
    applicationContext.close();
  }
}