DefaultListableBeanFactory

阳光穿透心脏的1/2处 2024-02-18 10:04 12阅读 0赞

DefaultListableBeanFactory 是一个完整的、功能成熟的 IoC 容器，如果你的需求很简单，甚至可以直接使用 DefaultListableBeanFactory，如果你的需求比较复杂，那么通过扩展 DefaultListableBeanFactory 的功能也可以达到，可以说 DefaultListableBeanFactory 是整个 Spring IoC 容器的始祖。

![5d835410c14042648b3958f32c3a8d57.png][]

新建两个实体类User和UserMessage类和一个配置类MyConfig

@Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class UserMessage {
    
        private String phone;
        private String address;
    }
    
    
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class User {
       private String username;
    
       @Autowired
       private UserMessage userMessage;
    }
    
    
    public class MyConfig {
    
        @Bean
        public User user(){
            return new User();
        }
    
        @Bean
        public UserMessage userMessage(){
            return new UserMessage("17860397188","123456");
        }
    }

动态注册 Bean，这是 DefaultListableBeanFactory 的功能之一，不过准确来说应该是动态注册 BeanDefinition 。

DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
            AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(MyConfig.class).getBeanDefinition();
            beanFactory.registerBeanDefinition("config",beanDefinition);
    
            AnnotationConfigUtils.registerAnnotationConfigProcessors(beanFactory); //为beanfactory添加后处理器
            //beanfactory 后处理器解析@Bean等注解
            Map<String, BeanFactoryPostProcessor> beansOfType = beanFactory.getBeansOfType(BeanFactoryPostProcessor.class);
            beansOfType.values().forEach(i->i.postProcessBeanFactory(beanFactory));
            //Bean后处理器，针对Bean生命周期的各个阶段提供扩展，例如@Autowired
            beanFactory.getBeansOfType(BeanPostProcessor.class).values().forEach(beanFactory::addBeanPostProcessor);
    
            Arrays.stream(beanFactory.getBeanDefinitionNames()).forEach(i-> System.out.println(i));
            User user = (User) beanFactory.getBean("user");
            System.out.println(user.getUserMessage());

Bean 的懒加载。这个时候先把 BeanDefinition 定义好，等到真正调用 Bean 的时候，才会去初始化 Bean。在 DefaultListableBeanFactory 中还有一个 preInstantiateSingletons 方法可以提前注册 Bean，该方法是在 ConfigurableListableBeanFactory 接口中声明的，DefaultListableBeanFactory 类实现了 ConfigurableListableBeanFactory 接口并实现了接口中的方法。

@Override
    public void preInstantiateSingletons() throws BeansException {
    	if (logger.isTraceEnabled()) {
    		logger.trace("Pre-instantiating singletons in " + this);
    	}
    	// Iterate over a copy to allow for init methods which in turn register new bean definitions.
    	// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
    	List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
    	// Trigger initialization of all non-lazy singleton beans...
    	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 FactoryBean) {
    					final FactoryBean<?> factory = (FactoryBean<?>) bean;
    					boolean isEagerInit;
    					if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
    						isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
    										((SmartFactoryBean<?>) factory)::isEagerInit,
    								getAccessControlContext());
    					}
    					else {
    						isEagerInit = (factory instanceof SmartFactoryBean &&
    								((SmartFactoryBean<?>) factory).isEagerInit());
    					}
    					if (isEagerInit) {
    						getBean(beanName);
    					}
    				}
    			}
    			else {
    				getBean(beanName);
    			}
    		}
    	}
    	// Trigger post-initialization callback for all applicable beans...
    	for (String beanName : beanNames) {
    		Object singletonInstance = getSingleton(beanName);
    		if (singletonInstance instanceof SmartInitializingSingleton) {
    			final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
    			if (System.getSecurityManager() != null) {
    				AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
    					smartSingleton.afterSingletonsInstantiated();
    					return null;
    				}, getAccessControlContext());
    			}
    			else {
    				smartSingleton.afterSingletonsInstantiated();
    			}
    		}
    	}
    }

[5d835410c14042648b3958f32c3a8d57.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/18/f5d409cfa51b4289a2053b206d42537c.png