Spring BeanFactory 预初始化过程详解

beanFactory.preInstantiateSingletons(),初始化和实例化操作

1. 循环beanDefinitionNames中的名称，调用getBean(beanName)

   1. 调用doGetBean(name, null, null, false)

      1. ```java
         sharedInstance = getSingleton(beanName, () -> {
             try {
                 return createBean(beanName, mbd, args);
             } catch (BeansException ex) {
                 destroySingleton(beanName);
                 throw ex;
             }
         });
         //在getSingleton中调用这个lambda表达式中的createBean
         ```

         1. Object beanInstance = doCreateBean(beanName, mbdToUse, args)
            1. 实例化对象，instanceWrapper = createBeanInstance(beanName, mbd, args);
               1. instantiateBean(beanName, mbd)
                  1. beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent)
                     1. BeanUtils.instantiateClass(constructorToUse)
                        1. 实例化完成，return ctor.newInstance(argsWithDefaultValues)
            2. 添加到三级缓存中：addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
            3. 初始化，降属性赋值，populateBean(beanName, mbd, instanceWrapper);
               1. 开始填充属性值，通过AutowiredAnnotationBeanPostProcessor，InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
                  1. 元数据注入，metadata.inject(bean, beanName, pvs);
                     1. 循环有@autowire的属性，element.inject(target, beanName, pvs)
                        1. 解决依赖value = beanFactory.resolveDependency(desc, beanName, autowiredBeanNames, typeConverter);