Spring容器扩展点

Spring容器扩展点 BeanDefinitionRegistryPostProcessorBeanFactoryPostProcessorImportSelectorImportBeanDefinitionRegistorBeanPostProcessorInstantiationAwareBeanPostProcessor--postProcessBeforeInstantiationSmartInstantiationAwareBeanPostProcessor--determineCandidateConstructorsMergedBeanDefinitionPostProcessor--postProcessMergedBeanDefinitionSmartInstantiationAwareBeanPostProcessor--getEarlyBeanReferenceInstantiationAwareBeanPostProcessor--postProcessAfterInstantiationInstantiationAwareBeanPostProcessor--postProcessPropertiesBeanPostProcessor--postProcessBeforeInitializationBeanPostProcessor--postProcessAfterInitialization Aware--初始化阶段调用多种Bean初始化方法执行顺序Bean创建完成之后多种Bean销毁方法执行顺序

BeanDefinitionRegistryPostProcessor

用来注册BeanDefinition，后期可生成bean。processor本身也会注册为Bean。

@Component public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor { @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { //可以使用builder来获取BeanDefinition, 也可以手动创建 // BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(OrderService.class); // BeanDefinition beanDefinition1 = builder.getBeanDefinition(); RootBeanDefinition beanDefinition = new RootBeanDefinition(); beanDefinition.setBeanClass(OrderService.class); beanDefinition.getPropertyValues().add("orderId", 001); registry.registerBeanDefinition("orderService", beanDefinition); } @Configuration @ComponentScan public class AppConfig { } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { } } public class Main { public static void main(String[] args) { AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class); OrderService orderService = (OrderService) applicationContext.getBean("orderService"); System.out.println(orderService); } } BeanFactoryPostProcessor

可以注册/修改BeanDefinition，或者修改Bean工厂里面的Bean。processor本身也会注册为Bean。

@Component public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor { @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException { OrderService orderService = (OrderService) configurableListableBeanFactory.getBean("orderService"); orderService.setOrderId(2L); } } ImportSelector

配置@Import使用，导入需要生成Bean的类，最终生成的Bean名称与类名相同。selector本身不会成为Bean。

public class MyImportSelector implements ImportSelector { @Override public String[] selectImports(AnnotationMetadata annotationMetadata) { return new String[]{"com.hoitung.fyz.SpringPostProcessor.OrderService"}; } } @Configuration //@ComponentScan @Import(MyImportSelector.class) public class AppConfig { } public class Main { public static void main(String[] args) { AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class); //OrderService orderService = (OrderService) applicationContext.getBean("orderService"); OrderService orderService = applicationContext.getBean(OrderService.class); System.out.println(orderService); } } ImportBeanDefinitionRegistor

配合@Import使用，可以注册BeanDefinition，本身不会生成Bean。有个很重要的功能是可以获取@Import注解所在类的其他注解信息。MyBatis整合Spring使用了该方法。

public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar { @Override public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) { BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(OrderService.class); BeanDefinition beanDefinition = beanDefinitionBuilder.getBeanDefinition(); beanDefinitionRegistry.registerBeanDefinition("orderServiceImport", beanDefinition); //AnnotationMetadata 可获取import注解所在类的其他注解信息 System.out.println(annotationMetadata.getAnnotationAttributes(ComponentScan.class.getName())); } } @Configuration @ComponentScan @Import(MyImportBeanDefinitionRegistrar.class) public class AppConfig { } public class Main { public static void main(String[] args) { AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class); //OrderService orderService = (OrderService) applicationContext.getBean("orderService"); OrderService orderService = applicationContext.getBean(OrderService.class); System.out.println(orderService); } } BeanPostProcessor InstantiationAwareBeanPostProcessor–postProcessBeforeInstantiation

在createBean中实例化前调用，如果改后置处理器返回了一个Bean，后续流程不会走。

@Component public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor { public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException { //此处返回实例对象，中断bean的生命周期 if(beanName.equals("orderServiceImport")) { System.out.println(beanName+"实例化前返回对象，会中断bean的生命周期"); return new OrderService(); } else { //此处返回null，还会继续bean的生命周期 return InstantiationAwareBeanPostProcessor.super.postProcessBeforeInstantiation(beanClass, beanName); } } } SmartInstantiationAwareBeanPostProcessor–determineCandidateConstructors

bean实例化时调用，返回实例化可使用的构造函数。

@Component public class MySmartInstantiationAwareBeanPostProcessor implements SmartInstantiationAwareBeanPostProcessor { public Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, String beanName) throws BeansException { if(beanClass == OrderService.class) { try { return new Constructor[]{beanClass.getConstructor(Long.class)}; } catch (NoSuchMethodException e) { throw new RuntimeException(e); } } return SmartInstantiationAwareBeanPostProcessor.super.determineCandidateConstructors(beanClass, beanName); } } public class OrderService implements BeanNameAware { private Long orderId; private String beanName; public OrderService(Long orderId) { System.out.println("使用只有一个参数的构造器"); this.orderId = orderId; } public OrderService(Long orderId, String beanName) { System.out.println("使用有两个参数的构造器"); this.orderId = orderId; this.beanName = beanName; } public void setOrderId(Long orderId) { this.orderId = orderId; } @Override public void setBeanName(String s) { beanName = s; } @Override public String toString() { return "OrderService{" + "orderId=" + orderId + ", beanName='" + beanName + '\'' + '}'; } } @Configuration @ComponentScan @Import(MyImportBeanDefinitionRegistrar.class) public class AppConfig { @Bean public Long orderId() { return 10001L; } } public class Main { public static void main(String[] args) { AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class); //OrderService orderService = (OrderService) applicationContext.getBean("orderService"); OrderService orderService = applicationContext.getBean(OrderService.class); System.out.println(orderService); } }

运行结果：

使用只有一个参数的构造器 OrderService{orderId=10001, beanName='orderServiceImport'} MergedBeanDefinitionPostProcessor–postProcessMergedBeanDefinition

实例化后，为属性注入做准备，预解析@Autowired @Value。可以使用该方法修改beanDefinition属性注入的值。

@Component public class MyMergedBeanDefinitionPostProcessor implements MergedBeanDefinitionPostProcessor { @Override public void postProcessMergedBeanDefinition(RootBeanDefinition rootBeanDefinition, Class<?> aClass, String s) { if(aClass == OrderService.class) { System.out.println(s+"实例化后给属性注入做准备，可以给BeanDefinition指定注入的值"); rootBeanDefinition.getPropertyValues().add("orderId", 9000); } } } public class OrderService implements BeanNameAware { private Long orderId; private String beanName; // public OrderService(Long orderId) { // System.out.println("使用只有一个参数的构造器"); // this.orderId = orderId; // } // // public OrderService(Long orderId, String beanName) { // System.out.println("使用有两个参数的构造器"); // this.orderId = orderId; // this.beanName = beanName; // } public void setOrderId(Long orderId) { this.orderId = orderId; } @Override public void setBeanName(String s) { beanName = s; } @Override public String toString() { return "OrderService{" + "orderId=" + orderId + ", beanName='" + beanName + '\'' + '}'; } } public class Main { public static void main(String[] args) { AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class); //OrderService orderService = (OrderService) applicationContext.getBean("orderService"); OrderService orderService = applicationContext.getBean(OrderService.class); System.out.println(orderService); } }

运行结果：

orderServiceImport实例化后给属性注入做准备，可以给BeanDefinition指定注入的值 OrderService{orderId=9000, beanName='orderServiceImport'} SmartInstantiationAwareBeanPostProcessor–getEarlyBeanReference

主要用于处理循环依赖问题。getEarlyBeanReference方法允许在Bean完全初始化之前，提前返回一个Bean的早期引用，其他依赖该Bean的Bean可以使用这个早期引用，从而避免循环依赖导致的死锁问题。

InstantiationAwareBeanPostProcessor–postProcessAfterInstantiation

postProcessAfterInstantiation方法是Spring Bean生命周期中的一个重要扩展点，允许开发者在Bean实例化之后、属性填充之前执行自定义逻辑。返回true继续属性填充，返回false表示跳过属性填充。

@Component public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor { // public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException { // //此处返回实例对象，中断bean的生命周期 // if(beanName.equals("orderServiceImport")) { // System.out.println(beanName+"实例化前返回对象，会中断bean的生命周期"); // return new OrderService(1001L); // } else { // //此处返回null，还会继续bean的生命周期 // return InstantiationAwareBeanPostProcessor.super.postProcessBeforeInstantiation(beanClass, beanName); // } // } public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException { if(bean instanceof OrderService) { System.out.println(beanName+"跳过属性注入"); return false; } return true; } }

运行结果：

orderServiceImport跳过属性注入 OrderService{orderId=null, beanName='orderServiceImport'} InstantiationAwareBeanPostProcessor–postProcessProperties

属性填充阶段，开发者可以通过该方法对属性值进行修改或替换。

@Component public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor { public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) throws BeansException { if(bean instanceof OrderService) { MutablePropertyValues mpv = pvs instanceof MutablePropertyValues ? (MutablePropertyValues) pvs : new MutablePropertyValues(pvs); mpv.add("userName", "test"); return mpv; } return null; } } public class OrderService implements BeanNameAware { @Autowired private Long orderId; @Autowired private String userName; private String beanName; public void setUserName(String userName) { this.userName = userName; } public void setOrderId(Long orderId) { this.orderId = orderId; } @Override public void setBeanName(String s) { beanName = s; } @Override public String toString() { return "OrderService{" + "orderId=" + orderId + ", userName='" + userName + '\'' + ", beanName='" + beanName + '\'' + '}'; } }

运行结果：

OrderService{orderId=10001, userName='test', beanName='orderServiceImport'} BeanPostProcessor–postProcessBeforeInitialization

Bean的初始化方法执行之前，对Bean进行一些额外的处理

BeanPostProcessor–postProcessAfterInitialization

在Bean初始化方法执行之后调用，此时已经有完整的bean。

Aware–初始化阶段调用

ApplicationContextAware BeanFactoryAware BeanNameAware EmbeddedValueResolverAware–spel表达式解析 EnvironmentAware ApplicationEventPublisherAware–获取事件发布器，发布事件继承ApplicationEvent，实现ApplicationListener监听

public class OrderService implements BeanNameAware, ApplicationEventPublisherAware { @Autowired private Long orderId; @Autowired private String userName; private String beanName; private ApplicationEventPublisher applicationEventPublisher; public void placeOrder() { applicationEventPublisher.publishEvent(new OrderEvent(this, "orderEvent")); } public void setUserName(String userName) { this.userName = userName; } public void setOrderId(Long orderId) { this.orderId = orderId; } @Override public void setBeanName(String s) { beanName = s; } @Override public String toString() { return "OrderService{" + "orderId=" + orderId + ", userName='" + userName + '\'' + ", beanName='" + beanName + '\'' + '}'; } @Override public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) { this.applicationEventPublisher = applicationEventPublisher; } } public class OrderEvent extends ApplicationEvent { public OrderEvent(Object source, String msg) { super(source); System.out.println(msg); } } @Component public class OrderEventListener implements ApplicationListener<OrderEvent> { @Override public void onApplicationEvent(OrderEvent orderEvent) { System.out.println("监听到事件："+orderEvent.toString()); } }

MessageSourceAware–国际化 ResourceLoaderAware-资源加载器，加载类路径下的文件

@Component public class ResourceUtil implements ResourceLoaderAware { private ResourceLoader resourceLoader; @Override public void setResourceLoader(ResourceLoader resourceLoader) { this.resourceLoader = resourceLoader; } public void showResourceData() throws IOException { Resource resource = resourceLoader.getResource("classpath:spring.yml"); BufferedReader br = new BufferedReader(new InputStreamReader(resource.getInputStream())); while(true) { String s = br.readLine(); if(StringUtils.isEmpty(s)) { break; } System.out.println(s); } } }

resource下增加一个配置文件spring.xml:

order: userName: zls

运行结果：

order: userName: zls 多种Bean初始化方法执行顺序

@PostConstruct 实现接口InitializingBean的afterPropertiesSet方法 指定bean的init-method

Bean创建完成之后

SmartInitializingSingleton接口–所有Bean初始化完成之后调用 SmartLifecycle接口–spring容器加载完之后，可以做缓存预热，定时器启动关闭等 ContextRefreshedEvent–容器加载完成之后会发布这个事件，可以监听这个事件 ContextStoppedEvent ContextClosedEvent

多种Bean销毁方法执行顺序

@PreDestroy 实现DisposableBean接口的destroy方法 指定bean的destroy-method