springIOC源码接口分析(八):AutowireCapableBeanFactory

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:

springIOC源码接口分析(八):AutowireCapableBeanFactory_第1张图片

 

 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:

springIOC源码接口分析(八):AutowireCapableBeanFactory_第2张图片

不使用接口测试:

springIOC源码接口分析(八):AutowireCapableBeanFactory_第3张图片

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:
springIOC源码接口分析(八):AutowireCapableBeanFactory_第4张图片

 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:createBeanInstancepopulateBeaninitializeBean:

    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

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