Spring注解系列十六：生命周期-BeanPostProcessor使用

本是古典何须时尚 2022-02-03 00:47 254阅读 0赞

Spring底层对 BeanPostProcessor 的使用：bean赋值，注入其他组件，@Autowired，生命周期注解功能，@Async等等都是利用 BeanPostProcessor来完成的。  
1、BeanPostProcessor  
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2、ApplicationContextAwareProcessor。可以帮我们给组件中注入IOC容器

public class Dog implements ApplicationContextAware {
    
    	private ApplicationContext applicationContext;
    
    	@Override
    	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    		// TODO Auto-generated method stub
    		this.applicationContext = applicationContext;
    	}
    
    }

快捷键 Alt+7就显示ApplicationContextAwareProcessor中的所有方法  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70 1]

public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
        AccessControlContext acc = null;
        if (System.getSecurityManager() != null && (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware || bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware || bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
            acc = this.applicationContext.getBeanFactory().getAccessControlContext();
        }
    
        if (acc != null) {
            AccessController.doPrivileged(new PrivilegedAction<Object>() {
                public Object run() {
                    ApplicationContextAwareProcessor.this.invokeAwareInterfaces(bean);
                    return null;
                }
            }, acc);
        } else {
            this.invokeAwareInterfaces(bean);
        }
    
        return bean;
    }
    
    
    
    private void invokeAwareInterfaces(Object bean) {
        if (bean instanceof Aware) {
            if (bean instanceof EnvironmentAware) {
                ((EnvironmentAware)bean).setEnvironment(this.applicationContext.getEnvironment());
            }
    
            if (bean instanceof EmbeddedValueResolverAware) {
                ((EmbeddedValueResolverAware)bean).setEmbeddedValueResolver(this.embeddedValueResolver);
            }
    
            if (bean instanceof ResourceLoaderAware) {
                ((ResourceLoaderAware)bean).setResourceLoader(this.applicationContext);
            }
    
            if (bean instanceof ApplicationEventPublisherAware) {
                ((ApplicationEventPublisherAware)bean).setApplicationEventPublisher(this.applicationContext);
            }
    
            if (bean instanceof MessageSourceAware) {
                ((MessageSourceAware)bean).setMessageSource(this.applicationContext);
            }
    
            if (bean instanceof ApplicationContextAware) {
                ((ApplicationContextAware)bean).setApplicationContext(this.applicationContext);
            }
        }
    
    }

3、BeanValidationPostProcessor。用来做数据校验

public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (!this.afterInitialization) {
            this.doValidate(bean);
        }
    
        return bean;
    }
    
    
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (this.afterInitialization) {
            this.doValidate(bean);
        }
    
        return bean;
    }
    
    
    protected void doValidate(Object bean) {
        Set<ConstraintViolation<Object>> result = this.validator.validate(bean, new Class[0]);
        if (!result.isEmpty()) {
            StringBuilder sb = new StringBuilder("Bean state is invalid: ");
            Iterator it = result.iterator();
    
            while(it.hasNext()) {
                ConstraintViolation<Object> violation = (ConstraintViolation)it.next();
                sb.append(violation.getPropertyPath()).append(" - ").append(violation.getMessage());
                if (it.hasNext()) {
                    sb.append("; ");
                }
            }
    
            throw new BeanInitializationException(sb.toString());
        }
    }

4、InitDestroyAnnotationBeanPostProcessor。用来处理PostConstruct注解和PreDestroy注解

@Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    	LifecycleMetadata metadata = findLifecycleMetadata(bean.getClass());
    	try {
    		metadata.invokeInitMethods(bean, beanName);
    	}
    	catch (InvocationTargetException ex) {
    		throw new BeanCreationException(beanName, "Invocation of init method failed", ex.getTargetException());
    	}
    	catch (Throwable ex) {
    		throw new BeanCreationException(beanName, "Failed to invoke init method", ex);
    	}
    	return bean;
    }
    
    
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    	return bean;
    }

5、AutowiredAnnotationBeanPostProcessor。用来处理Autowired注解

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