spring源码分析六(Bean实例化的预处理)

今天这节内容我们一起来研究下,spring的bean的创建,我们一步步看着源码往下分析.下面的方法就会带我们进入bean的创建

完成bean工厂初始化
finishBeanFactoryInitialization(beanFactory);

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
        // 初始化类型转换器,这一部分的内容,就是说,当前端传过来的数据类型后台不好解析,可以通过这个实现这个接口来实现类类型转换
        //最典型的应用就是data转换
        if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
                beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
            beanFactory.setConversionService(
                    beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
        }

        //如果之前没有任何bean后处理器（例如PropertyPlaceholderConfigurer Bean）之前进行过注册，请注册默认的嵌入式值解析器，
        //主要用于注释属性值的解析
        if (!beanFactory.hasEmbeddedValueResolver()) {
            beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
        }

        // 初始化 LoadTimeWeaverAwareBean 用于织入第三方模块，在 class 文件载入 JVM 的时候动态织入
        String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
        for (String weaverAwareName : weaverAwareNames) {
            getBean(weaverAwareName);
        }

        //将临时类加载器设置为null
        beanFactory.setTempClassLoader(null);

        // 在初始化单例bean的过程中,先暂停bean的注册,解析加载等等
        beanFactory.freezeConfiguration();

        //初始化非懒加载的bean
        beanFactory.preInstantiateSingletons();
    }

其他方法都比较简单,咱们就直接从最后一个方法分析吧,这里干货满满哈
#DefaultListableBeanFactory
@Override
    public void preInstantiateSingletons() throws BeansException {
        if (logger.isTraceEnabled()) {
            logger.trace("Pre-instantiating singletons in " + this);
        }

        //将所有的bean定义名称添加到beanNames集合中
        List beanNames = new ArrayList<>(this.beanDefinitionNames);

        // 遍历所有的费懒加载的bean
        for (String beanName : beanNames) {
            //对bean定义进行合并,比如bean中引入属性parent这一步就是来处理这个属性的
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            //如果bean不是抽象的,不是懒加载的,并且是单例的,执行以下步骤
            if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                //判断是否是工厂bean
                if (isFactoryBean(beanName)) {
                    //如果是工厂bean,调用的时候再bean的名称前面添加前缀符号&
                    Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
                    //再次判断bean是否是factoryBean
                    if (bean instanceof FactoryBean) {
                        final FactoryBean factory = (FactoryBean) bean;
                        boolean isEagerInit;
                        if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                            isEagerInit = AccessController.doPrivileged((PrivilegedAction)
                                            ((SmartFactoryBean) factory)::isEagerInit,
                                    getAccessControlContext());
                        }
                        else {
                            isEagerInit = (factory instanceof SmartFactoryBean &&
                                    ((SmartFactoryBean) factory).isEagerInit());
                        }
                        if (isEagerInit) {
                            getBean(beanName);
                        }
                    }
                }
                else {
                    getBean(beanName);
                }
            }
        }

        //再次遍历beanNames,对实现了SmartInitializingSingleton接口的类实现处理,这里也就是说,他的功能类似于InitzationBean合格接口
        //在单例bean加载完成后,做一些事情
        for (String beanName : beanNames) {
            Object singletonInstance = getSingleton(beanName);
            if (singletonInstance instanceof SmartInitializingSingleton) {
                final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
                if (System.getSecurityManager() != null) {
                    AccessController.doPrivileged((PrivilegedAction