精彩的内容来了，各位看官，继续~
接上一节，AbstractApplicationContext 类中的refresh()方法，有那么一行不起眼的代码：
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
就是它，创建bean最集中的地方，实例化所有非懒加载的单例。
点击这个方法进去，可以看到方法体内又有一行代码：
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
真正干活的爷们就是它了。再点进去，可以看到方法实现：
preInstantiateSingletons.png
getMergedLocalBeanDefinition(beanName) ，将BeanDefinition的定义进行合并
if (isFactoryBean(beanName)) {……} ，判断是不是FactoryBean，拿到FactoryBean的实例，判断是否需要提前实例化，需要则通过getBean来实例化
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getBean(beanName) 普通bean的实例化，点进去，来到doGetBean()，上码：
protected <T> T doGetBean( String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)throws BeansException { // 获取真实的beanName,因为有的bean有别名，FactoryBean本身创建的时候，传的是&BeanName String beanName = transformedBeanName(name); Object beanInstance; // 从缓存获取单例实例，解决循环依赖和重复创建 Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { if (logger.isTraceEnabled()) { if (isSingletonCurrentlyInCreation(beanName)) { logger.trace("……"); } else { logger.trace("……"); } } //解决类似FactoryBean这样特殊的bean处理 beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { // 原型模式不需解决循环依赖，因为原型bean不放缓存，不会提前暴露引用 if (isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } // 如果 beanDefinitionMap未加载有该bean，则从parentBeanFactory查找 BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { String nameToLookup = originalBeanName(name); if (parentBeanFactory instanceof AbstractBeanFactory) { return ((AbstractBeanFactory) parentBeanFactory).doGetBean( nameToLookup, requiredType, args, typeCheckOnly); } else if (args != null) { return (T) parentBeanFactory.getBean(nameToLookup, args); } else if (requiredType != null) { return parentBeanFactory.getBean(nameToLookup, requiredType); } else { return (T) parentBeanFactory.getBean(nameToLookup); } } // 非类型检查的时候，才标记该bean已创建 if (!typeCheckOnly) { markBeanAsCreated(beanName); } StartupStep beanCreation = this.applicationStartup.start("spring.beans.instantiate") .tag("beanName", name); try { if (requiredType != null) { beanCreation.tag("beanType", requiredType::toString); } RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); // 当前bean依赖的bean的创建。 String[] dependsOn = mbd.getDependsOn(); if (dependsOn != null) { for (String dep : dependsOn) { // 不可显式依赖(@DependOn) if (isDependent(beanName, dep)) { throw new BeanCreationException("……"); } // 先创建依赖的bean，再创建本身自己 registerDependentBean(dep, beanName); try { getBean(dep); } catch (NoSuchBeanDefinitionException ex) { throw new BeanCreationException("……"); } } } // 单例bean创建 if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, () -> { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { destroySingleton(beanName); throw ex; } }); beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } // 原型bean创建 else if (mbd.isPrototype()) { Object prototypeInstance = null; try { beforePrototypeCreation(beanName); prototypeInstance = createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } beanInstance = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } // 指定scope上实例化bean else { String scopeName = mbd.getScope(); if (!StringUtils.hasLength(scopeName)) { throw new IllegalStateException("……"); } Scope scope = this.scopes.get(scopeName); if (scope == null) { throw new IllegalStateException("……"); } try { Object scopedInstance = scope.get(beanName, () -> { beforePrototypeCreation(beanName); try { return createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } }); beanInstance = getObjectForBeanInstance(scopedInstance, name, beanName, mbd); } catch (IllegalStateException ex) { throw new ScopeNotActiveException(beanName, scopeName, ex); } } } catch (BeansException ex) { beanCreation.tag("exception", ex.getClass().toString()); beanCreation.tag("message", String.valueOf(ex.getMessage())); cleanupAfterBeanCreationFailure(beanName); throw ex; } finally { beanCreation.end(); } } // 检查实际类型与所需类型是否符合，不符合则装换 return adaptBeanInstance(name, beanInstance, requiredType); }以上代码中，创建bean的地方是:
createBean(beanName, mbd, args);点击该方法进去，还藏有一层：
doCreateBean(beanName, mbdToUse, args);点击该方法进去，就是真正创建bean的地方。下节再讲，喝口酒先~~
