参考博文: https://blog.csdn.net/f641385712/article/details/88651128
一 接口规范
从宏观上看,AutowireCapableBeanFactory提供了如下能力:
1 为已经实例化的对象装配属性,这些属性对象都是Spring管理的;
2 实例化一个Bean,并自动装配,这些被装配的属性对象都是Spring管理的,但是实例化的Bean可以不被Spring管理(这点特别重要)。所以这个接口提供功能就是自动装配bean相关的
(自动装配的原对象可以不在Spring的IOC容器里,但是需要被依赖注入的成员,就必须是Spring容器管辖的Bean)
此接口主要是针对框架之外,没有向Spring托管Bean的应用。通过暴露此功能,Spring框架之外的程序,也能具有自动装配的能力(此接口赋予它的)。
可以使用这个接口集成其它框架。捆绑并填充(注入)并不由Spring管理生命周期并已存在的实例.像集成WebWork的Actions 和Tapestry Page就很实用
一般应用开发者不会使用这个接口,所以像ApplicationContext这样的外观实现类不会实现这个接口,
但是提供了getAutowireCapableBeanFactory()方法允许你拿这个工具去做你需要的事。
接口定义:
public interface AutowireCapableBeanFactory01 extends BeanFactory { /** * 表明工厂没有自动装配的Bean */ int AUTOWIRE_NO = 0; /** * 表明根据名称自动装配 */ int AUTOWIRE_BY_NAME = 1; /** * 表明根据类型自动装配 */ int AUTOWIRE_BY_TYPE = 2; /** * 表明根据构造方法快速装配 */ int AUTOWIRE_CONSTRUCTOR = 3; @Deprecated // 表明通过Bean的class的内部来自动装配 Spring3.0被弃用。 int AUTOWIRE_AUTODETECT = 4; String ORIGINAL_INSTANCE_SUFFIX = ".ORIGINAL"; /** * 创建一个指定class的实例 */T createBean(Class beanClass) throws BeansException; /** * 通过调用给定Bean的after-instantiation及post-processing接口,对bean进行配置 */ void autowireBean(Object existingBean) throws BeansException; /** * 自动装配属性,填充属性值,使用诸如setBeanName,setBeanFactory这样的工厂回调填充属性,最好还要调用post processor */ Object configureBean(Object existingBean, String beanName) throws BeansException; /** * 创建一个指定class的实例,通过参数可以指定其自动装配模式(by-name or by-type). */ Object createBean(Class beanClass, int autowireMode, boolean dependencyCheck) throws BeansException; /** * 通过指定的自动装配策略来初始化一个Bean */ Object autowire(Class beanClass, int autowireMode, boolean dependencyCheck) throws BeansException; /** * 通过指定的自动装配方式来对给定的Bean进行自动装配 */ void autowireBeanProperties(Object existingBean, int autowireMode, boolean dependencyCheck) throws BeansException; /** * 将参数中指定了那么的Bean,注入给定实例当中 */ void applyBeanPropertyValues(Object existingBean, String beanName) throws BeansException; /** * 初始化参数中指定的Bean,调用任何其注册的回调函数如setBeanName、setBeanFactory等。 */ Object initializeBean(Object existingBean, String beanName) throws BeansException; /** * 调用参数中指定Bean的postProcessBeforeInitialization方法 */ Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName) throws BeansException; /** * 调用参数中指定Bean的postProcessAfterInitialization方法 */ Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName) throws BeansException; /** * 销毁参数中指定的Bean,同时调用此Bean上的DisposableBean和DestructionAwareBeanPostProcessors方法 */ void destroyBean(Object existingBean); /** * 查找唯一符合指定类的实例,如果有,则返回实例的名字和实例本身 * 底层依赖于:BeanFactory中的getBean(Class)方法 */ NamedBeanHolder resolveNamedBean(Class requiredType) throws BeansException; /** * 解析出在Factory中与指定Bean有指定依赖关系的Bean(@Autowired依赖注入的核心方法) */ Object resolveBeanByName(String name, DependencyDescriptor descriptor) throws BeansException; @Nullable Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName) throws BeansException; @Nullable Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName, @Nullable Set autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException; }
二 实际应用
准备一个外部类,即不被spring容器管理:
public class Person { //不使用@Autowired private User user; public User getUser() { return user; } public void setUser(User user) { this.user = user; } }
spring管理的User bean进行实例化,这里以spring-bean.xml为例:
利用AutowireCapableBeanFactory创建Bean:
public class BeanTest{ @Test public void beanTest(){ ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-bean.xml"); //ApplicationContext没有实现接口,但是可以通过方法直接获取使用 AutowireCapableBeanFactory autowireCapableBeanFactory = applicationContext.getAutowireCapableBeanFactory(); // autowireCapableBeanFactory创建Bean实例,执行多次就创建多个 Person person = (Person) autowireCapableBeanFactory.createBean(Person.class, AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE, false); //没有@Autowired注解也直接给注入了 System.out.println("获取自动注入的属性:"+person.getUser()); //异常: No qualifying bean of type 'com.hou.spring.Person' available Person bean = applicationContext.getBean(Person.class);//没有交给spring容器管理 System.out.println(bean); } }
执行结果:
不使用接口测试:
三 源码分析
主要从createBean方法进行分析:
这个接口调用的方法是在AbstractAutowireCapableBeanFactory抽象类中实现的:
@Override public Object createBean(Class beanClass, int autowireMode, boolean dependencyCheck) throws BeansException { // Use non-singleton bean definition, to avoid registering bean as dependent bean. RootBeanDefinition bd = new RootBeanDefinition(beanClass, autowireMode, dependencyCheck); //这里设置为原型,而不是单例,所以调用多次会生成多个对象 bd.setScope(BeanDefinition.SCOPE_PROTOTYPE); return createBean(beanClass.getName(), bd, null); }
然后就是return里面调用的createBean方法,这个是AbstractAutowireCapableBeanFactory类的父类AbstractBeanFactory定义的抽象方法:
AbstractAutowireCapableBeanFactory类中实现了这个抽象方法,这个方法很单纯:创建一个实例,然后初始化他(给属性们赋值),然后return出去即可:
@Override protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { if (logger.isTraceEnabled()) { logger.trace("Creating instance of bean '" + beanName + "'"); } RootBeanDefinition mbdToUse = mbd; // Make sure bean class is actually resolved at this point, and // clone the bean definition in case of a dynamically resolved Class // which cannot be stored in the shared merged bean definition. Class resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } try { mbdToUse.prepareMethodOverrides(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(), beanName, "Validation of method overrides failed", ex); } try { //若BeanPostProcessors 产生了一个代理对象,就不需要我去创建了,就不继续往下走了(AOP都走这里) Object bean = resolveBeforeInstantiation(beanName, mbdToUse); if (bean != null) { return bean; } } catch (Throwable ex) { throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "BeanPostProcessor before instantiation of bean failed", ex); } try { //本类的一个protected方法,专门用于处理创建Bean的过程(包括属性赋值之类的) Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (logger.isTraceEnabled()) { logger.trace("Finished creating instance of bean '" + beanName + "'"); } return beanInstance; } catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) { throw ex; } catch (Throwable ex) { throw new BeanCreationException( mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex); } }
再看本类的doCreateBean方法,主要有三个核心步骤三个步骤:createBeanInstance
、populateBean
、initializeBean:
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args) throws BeanCreationException { // Instantiate the bean. BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { //创建Bean实例,返回一个BeanWrapper,它也是本类的一个protected方法 instanceWrapper = createBeanInstance(beanName, mbd, args); } final Object bean = instanceWrapper.getWrappedInstance(); Class beanType = instanceWrapper.getWrappedClass(); if (beanType != NullBean.class) { mbd.resolvedTargetType = beanType; } // 处理循环引用,现在若我们Bean不在容器里,肯定是不存在循环引用的(但是我依赖的Bean可能还没创建是真的,也是这里来处理的) synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { try { applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); } catch (Throwable ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Post-processing of merged bean definition failed", ex); } mbd.postProcessed = true; } } // Eagerly cache singletons to be able to resolve circular references // even when triggered by lifecycle interfaces like BeanFactoryAware. boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName)); if (earlySingletonExposure) { if (logger.isTraceEnabled()) { logger.trace("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); } Object exposedObject = bean; try { //// 给Bean实例的各个属性进行赋值 populateBean(beanName, mbd, instanceWrapper); //初始化Bean 执行一些初始化方法init @PostContruct方法等等 exposedObject = initializeBean(beanName, exposedObject, mbd); }
其他具体细节以后其他博文专门记录笔记