容器管理bean的生命週期
- 我們可以自定義初始化和銷燬方法;容器在bean進行到當前生命週期的時候來調用我們自定義的初始化和銷燬方法
//@Scope("prototype")
@Bean(initMethod="init",destroyMethod="detory")
public Car car(){
return new Car();
}
- 構造(對象創建)
-
單實例(@Scope="singleton"):在容器啓動的時候創建對象
-
多實例(@Scope="prototype) :在每次獲取的時候創建對象
- 通過實現InitializingBean,DisposableBean 重寫 destroy和afterPropertiesSet方法進行初始化時和銷燬時的操作
@Component
public class Cat implements InitializingBean,DisposableBean {
public Cat(){
System.out.println("cat constructor...");
}
@Override
public void destroy() throws Exception {
// TODO Auto-generated method stub
System.out.println("cat...destroy...");
}
@Override
public void afterPropertiesSet() throws Exception {
// TODO Auto-generated method stub
System.out.println("cat...afterPropertiesSet...");
}
}
- 可以使用JSR250;
-
@PostConstruct:在bean創建完成並且屬性賦值完成;來執行初始化方法
-
@PreDestroy:在容器銷燬bean之前通知我們進行清理工作
寫在類的方法上類似於AOP
@Component
public class Dog implements ApplicationContextAware {
//@Autowired
private ApplicationContext applicationContext;
public Dog(){
System.out.println("dog constructor...");
}
//對象創建並賦值之後調用
@PostConstruct
public void init(){
System.out.println("Dog....@PostConstruct...");
}
//容器移除對象之前
@PreDestroy
public void detory(){
System.out.println("Dog....@PreDestroy...");
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
// TODO Auto-generated method stub
this.applicationContext = applicationContext;
}
}
4)BeanPostProcessor【interface】:bean的後置處理器;
在bean初始化前後進行一些處理工作;
-
postProcessBeforeInitialization:在初始化之前工作
-
postProcessAfterInitialization:在初始化之後工作
還要將實現類放入容器
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
// TODO Auto-generated method stub
System.out.println("postProcessBeforeInitialization..."+beanName+"=>"+bean);
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
// TODO Auto-generated method stub
System.out.println("postProcessAfterInitialization..."+beanName+"=>"+bean);
return bean;
}
}
BeanProcessor的原理:
- 遍歷得到容器中所有的BeanPostProcessor;挨個執行beforeInitialization,
- 一但返回null,跳出for循環,不會執行後面的BeanPostProcessor.postProcessorsBeforeInitialization
- BeanPostProcessor原理
- populateBean(beanName, mbd, instanceWrapper);給bean進行屬性賦值
- initializeBean
- {
- applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
- invokeInitMethods(beanName, wrappedBean, mbd);執行自定義初始化
- applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
*}
Spring底層對 BeanPostProcessor 的使用;
bean賦值,注入其他組件,@Autowired,生命週期註解功能,@Async,xxx BeanPostProcessor;