-----------------------------------------------------本文只作为跟代码的一个参考，建议可以根据思路在指定类中断点调试学习------------------------------------------------------------
运行被@SpringBootApplication修饰的程序入口，执行main方法，调用SpringApplication的run方法。
下面是从创建controller层bean的方法调用链如下：（备注：controller层做了通过mybaits连接数据库返回查询结果的操作）以下是倒序描述
// 这里就是调用了SqlsessionTemplate的构造方法
<init>:94, SqlSessionTemplate (org.mybatis.spring) sqlSessionTemplate:163, MybatisAutoConfiguration (org.mybatis.spring.boot.autoconfigure) CGLIB$sqlSessionTemplate$1:-1, MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$2abe972c (org.mybatis.spring.boot.autoconfigure) invoke:-1, MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$2abe972c$$FastClassBySpringCGLIB$$d1075e2f (org.mybatis.spring.boot.autoconfigure) invokeSuper:244, MethodProxy (org.springframework.cglib.proxy) intercept:363, ConfigurationClassEnhancer$BeanMethodInterceptor (org.springframework.context.annotation) sqlSessionTemplate:-1, MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$2abe972c (org.mybatis.spring.boot.autoconfigure) invoke0:-1, NativeMethodAccessorImpl (sun.reflect) invoke:62, NativeMethodAccessorImpl (sun.reflect) invoke:43, DelegatingMethodAccessorImpl (sun.reflect) invoke:498, Method (java.lang.reflect) instantiate:154, SimpleInstantiationStrategy (org.springframework.beans.factory.support) instantiate:651, ConstructorResolver (org.springframework.beans.factory.support) instantiateUsingFactoryMethod:636, ConstructorResolver (org.springframework.beans.factory.support) instantiateUsingFactoryMethod:1338, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) createBeanInstance:1177, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)//这里和其他bean的创建是不一样的，后面的操作也是在这个方法中执行的，执行完这个方法的后续操作和其他bean是一样的 doCreateBean:557, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) createBean:517, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) lambda$doGetBean$0:323, AbstractBeanFactory (org.springframework.beans.factory.support) getObject:-1, 1658980982 (org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$145) getSingleton:222, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support) doGetBean:321, AbstractBeanFactory (org.springframework.beans.factory.support) getBean:202, AbstractBeanFactory (org.springframework.beans.factory.support)
//5、这里开始创建SqlSessionTemplate实例 resolveCandidate:276, DependencyDescriptor (org.springframework.beans.factory.config) doResolveDependency:1287, DefaultListableBeanFactory (org.springframework.beans.factory.support) resolveDependency:1207, DefaultListableBeanFactory (org.springframework.beans.factory.support) autowireByType:1511, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) populateBean:1406, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) doCreateBean:594, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) createBean:517, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) lambda$doGetBean$0:323, AbstractBeanFactory (org.springframework.beans.factory.support) getObject:-1, 1658980982 (org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$145) getSingleton:222, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support) doGetBean:321, AbstractBeanFactory (org.springframework.beans.factory.support) getBean:202, AbstractBeanFactory (org.springframework.beans.factory.support)
//4、开始创建mapper接口代理实例 resolveCandidate:276, DependencyDescriptor (org.springframework.beans.factory.config) doResolveDependency:1287, DefaultListableBeanFactory (org.springframework.beans.factory.support) resolveDependency:1207, DefaultListableBeanFactory (org.springframework.beans.factory.support) autowireResource:537, CommonAnnotationBeanPostProcessor (org.springframework.context.annotation) getResource:513, CommonAnnotationBeanPostProcessor (org.springframework.context.annotation) getResourceToInject:653, CommonAnnotationBeanPostProcessor$ResourceElement (org.springframework.context.annotation) inject:224, InjectionMetadata$InjectedElement (org.springframework.beans.factory.annotation) inject:116, InjectionMetadata (org.springframework.beans.factory.annotation) postProcessProperties:334, CommonAnnotationBeanPostProcessor (org.springframework.context.annotation) populateBean:1422, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) doCreateBean:594, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) createBean:517, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) lambda$doGetBean$0:323, AbstractBeanFactory (org.springframework.beans.factory.support) getObject:-1, 1658980982 (org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$145) getSingleton:222, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support) doGetBean:321, AbstractBeanFactory (org.springframework.beans.factory.support) getBean:202, AbstractBeanFactory (org.springframework.beans.factory.support)
// 3、开始创建manager层bean resolveCandidate:276, DependencyDescriptor (org.springframework.beans.factory.config) doResolveDependency:1287, DefaultListableBeanFactory (org.springframework.beans.factory.support) resolveDependency:1207, DefaultListableBeanFactory (org.springframework.beans.factory.support) autowireResource:537, CommonAnnotationBeanPostProcessor (org.springframework.context.annotation) getResource:513, CommonAnnotationBeanPostProcessor (org.springframework.context.annotation) getResourceToInject:653, CommonAnnotationBeanPostProcessor$ResourceElement (org.springframework.context.annotation) inject:224, InjectionMetadata$InjectedElement (org.springframework.beans.factory.annotation) inject:116, InjectionMetadata (org.springframework.beans.factory.annotation) postProcessProperties:334, CommonAnnotationBeanPostProcessor (org.springframework.context.annotation) populateBean:1422, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) doCreateBean:594, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) createBean:517, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) lambda$doGetBean$0:323, AbstractBeanFactory (org.springframework.beans.factory.support) getObject:-1, 1658980982 (org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$145) getSingleton:222, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support) // 循环调用创建bean的方法 doGetBean:321, AbstractBeanFactory (org.springframework.beans.factory.support) getBean:202, AbstractBeanFactory (org.springframework.beans.factory.support)
// 2、开始创建service层bean resolveCandidate:276, DependencyDescriptor (org.springframework.beans.factory.config) // 根据解析到的依赖bean列表创建需要的bean doResolveDependency:1287, DefaultListableBeanFactory (org.springframework.beans.factory.support) resolveDependency:1207, DefaultListableBeanFactory (org.springframework.beans.factory.support) inject:640, AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement (org.springframework.beans.factory.annotation) //根据之前放到DefaultListableBeanFactory中的beanDefinitionMap集合中的对应bean的BeanDefinition信息获得需要注入的bean列表 inject:116, InjectionMetadata (org.springframework.beans.factory.annotation) postProcessProperties:399, AutowiredAnnotationBeanPostProcessor (org.springframework.beans.factory.annotation) populateBean:1422, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) doCreateBean:594, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) createBean:517, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support) lambda$doGetBean$0:323, AbstractBeanFactory (org.springframework.beans.factory.support) getObject:-1, 1658980982 (org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$145) getSingleton:222, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support)
//1、 开始创建单例controller层的bean doGetBean:321, AbstractBeanFactory (org.springframework.beans.factory.support) getBean:202, AbstractBeanFactory (org.springframework.beans.factory.support) preInstantiateSingletons:879, DefaultListableBeanFactory (org.springframework.beans.factory.support) finishBeanFactoryInitialization:878, AbstractApplicationContext (org.springframework.context.support)//这里开始创建bean refresh:550, AbstractApplicationContext (org.springframework.context.support) // 走到这里就和SpringMvc启动调用的是同一个bean初始化方法了
(注：其实这里和springmvc启动的不同之处就在用加载配置不同，加载完配置还是调用了统一的启动容器，创建bean，自动装配) refresh:141, ServletWebServerApplicationContext (org.springframework.boot.web.servlet.context) refresh:747, SpringApplication (org.springframework.boot) refreshContext:397, SpringApplication (org.springframework.boot) run:315, SpringApplication (org.springframework.boot) run:1226, SpringApplication (org.springframework.boot) run:1215, SpringApplication (org.springframework.boot) main:12, DemoApplication (com.example.mybatisdemo) 应用入口
下图是springboot启动需要自动装配的集合内容，会缓存到beanFactory 的beanDefinitionMap中
springboot的指定bean工厂是DefaultListableBeanFactory
下面来总结下整个流程：
1、 AbstractApplicationContext中的refresh()方法执行自身的finishBeanFactoryInitialization()方法。这个方法执行了具体实例化bean的工作
2、finishBeanFactoryInitialization方法调用了bean工厂的对应方法对不同bean进行实例化。
3、spring的bean默认都是单例的，现在一单例bean的创建为例继续跟踪。spring调用了bean工厂的preInstantiateSingletons()方法。
4、在bean工程的创建实例的方法中循环创建了工厂实现缓存好的beanDefineNames列表中对应的bean.
0 = "org.springframework.context.annotation.internalConfigurationAnnotationProcessor" 1 = "org.springframework.context.annotation.internalAutowiredAnnotationProcessor" 2 = "org.springframework.context.annotation.internalCommonAnnotationProcessor" 3 = "org.springframework.context.event.internalEventListenerProcessor" 4 = "org.springframework.context.event.internalEventListenerFactory" 5 = "demoApplication" 6 = "org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory" 7 = "demoController" 8 = "demoManager" 9 = "demoServiceImpl" 10 = "org.springframework.boot.autoconfigure.AutoConfigurationPackages" 11 = "cfDirectRepaymentRecordMapper" 12 = "weeklyMapper" 13 = "org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration" 14 = "propertySourcesPlaceholderConfigurer" 15 = "org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration$TomcatWebSocketConfiguration" 16 = "websocketServletWebServerCustomizer" 17 = "org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration" 18 = "org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryConfiguration$EmbeddedTomcat" 19 = "tomcatServletWebServerFactory" 20 = "org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration" 21 = "servletWebServerFactoryCustomizer" 22 = "tomcatServletWebServerFactoryCustomizer" 23 = "org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor" 24 = "org.springframework.boot.context.internalConfigurationPropertiesBinderFactory" 25 = "org.springframework.boot.context.internalConfigurationPropertiesBinder" 26 = "org.springframework.boot.context.properties.ConfigurationPropertiesBeanDefinitionValidator" 27 = "org.springframework.boot.context.properties.ConfigurationBeanFactoryMetadata" 28 = "server-org.springframework.boot.autoconfigure.web.ServerProperties" 29 = "webServerFactoryCustomizerBeanPostProcessor" 30 = "errorPageRegistrarBeanPostProcessor" 31 = "org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration$DispatcherServletConfiguration" 32 = "dispatcherServlet" 33 = "spring.http-org.springframework.boot.autoconfigure.http.HttpProperties" 34 = "spring.mvc-org.springframework.boot.autoconfigure.web.servlet.WebMvcProperties" 35 = "org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration$DispatcherServletRegistrationConfiguration" 36 = "dispatcherServletRegistration" 37 = "org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration" 38 = "org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration" 39 = "taskExecutorBuilder" 40 = "applicationTaskExecutor" 41 = "spring.task.execution-org.springframework.boot.autoconfigure.task.TaskExecutionProperties" 42 = "org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration" 43 = "defaultValidator" 44 = "methodValidationPostProcessor" 45 = "org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration" 46 = "error" 47 = "beanNameViewResolver" 48 = "org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$DefaultErrorViewResolverConfiguration" 49 = "conventionErrorViewResolver" 50 = "org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration" 51 = "errorAttributes" 52 = "basicErrorController" 53 = "errorPageCustomizer" 54 = "preserveErrorControllerTargetClassPostProcessor" 55 = "spring.resources-org.springframework.boot.autoconfigure.web.ResourceProperties" 56 = "org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$EnableWebMvcConfiguration" 57 = "requestMappingHandlerAdapter" 58 = "requestMappingHandlerMapping" 59 = "welcomePageHandlerMapping" 60 = "mvcConversionService" 61 = "mvcValidator" 62 = "mvcContentNegotiationManager" 63 = "mvcPathMatcher" 64 = "mvcUrlPathHelper" 65 = "viewControllerHandlerMapping" 66 = "beanNameHandlerMapping" 67 = "routerFunctionMapping" 68 = "resourceHandlerMapping" 69 = "mvcResourceUrlProvider" 70 = "defaultServletHandlerMapping" 71 = "handlerFunctionAdapter" 72 = "mvcUriComponentsContributor" 73 = "httpRequestHandlerAdapter" 74 = "simpleControllerHandlerAdapter" 75 = "handlerExceptionResolver" 76 = "mvcViewResolver" 77 = "mvcHandlerMappingIntrospector" 78 = "org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter" 79 = "defaultViewResolver" 80 = "viewResolver" 81 = "requestContextFilter" 82 = "org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration" 83 = "formContentFilter" 84 = "com.alibaba.druid.spring.boot.autoconfigure.stat.DruidStatViewServletConfiguration" 85 = "statViewServletRegistrationBean" 86 = "com.alibaba.druid.spring.boot.autoconfigure.stat.DruidWebStatFilterConfiguration" 87 = "webStatFilterRegistrationBean" 88 = "com.alibaba.druid.spring.boot.autoconfigure.stat.DruidFilterConfiguration" 89 = "statFilter" 90 = "com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceAutoConfigure" 91 = "dataSource" 92 = "spring.datasource.druid-com.alibaba.druid.spring.boot.autoconfigure.properties.DruidStatProperties" 93 = "spring.datasource-org.springframework.boot.autoconfigure.jdbc.DataSourceProperties" 94 = "org.springframework.boot.autoconfigure.jdbc.metadata.DataSourcePoolMetadataProvidersConfiguration$HikariPoolDataSourceMetadataProviderConfiguration" 95 = "hikariPoolDataSourceMetadataProvider" 96 = "org.springframework.boot.autoconfigure.jdbc.metadata.DataSourcePoolMetadataProvidersConfiguration" 97 = "org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker" 98 = "org.springframework.boot.autoconfigure.jdbc.DataSourceInitializationConfiguration" 99 = "dataSourceInitializerPostProcessor"
public void preInstantiateSingletons() throws BeansException { if (this.logger.isTraceEnabled()) { this.logger.trace("Pre-instantiating singletons in " + this); } List<String> beanNames = new ArrayList(this.beanDefinitionNames); Iterator var2 = beanNames.iterator(); while(true) { String beanName; Object bean; do { while(true) { RootBeanDefinition bd; do { do { do { if (!var2.hasNext()) { var2 = beanNames.iterator(); while(var2.hasNext()) { beanName = (String)var2.next(); Object singletonInstance = this.getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton)singletonInstance; if (System.getSecurityManager() != null) { AccessController.doPrivileged(() -> { smartSingleton.afterSingletonsInstantiated(); return null; }, this.getAccessControlContext()); } else { smartSingleton.afterSingletonsInstantiated(); } } } return; } beanName = (String)var2.next(); bd = this.getMergedLocalBeanDefinition(beanName); } while(bd.isAbstract()); } while(!bd.isSingleton()); } while(bd.isLazyInit()); if (this.isFactoryBean(beanName)) { bean = this.getBean("&" + beanName); break; } this.getBean(beanName); } } while(!(bean instanceof FactoryBean)); FactoryBean<?> factory = (FactoryBean)bean; boolean isEagerInit; if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) { SmartFactoryBean var10000 = (SmartFactoryBean)factory; ((SmartFactoryBean)factory).getClass(); isEagerInit = (Boolean)AccessController.doPrivileged(var10000::isEagerInit, this.getAccessControlContext()); } else { isEagerInit = factory instanceof SmartFactoryBean && ((SmartFactoryBean)factory).isEagerInit(); } if (isEagerInit) { this.getBean(beanName); } } }
5、在循环构造实例的方法中调用了从抽象父类AbstractBeanFactory继承来的this.getBean(beanName);方法。
通过细心看代码，通过工厂模式创建bean和通过类自身的构造方法创建bean的流程是不一样的，这里通过在beanName上加&符作为区分
6、接下来看下我们自定义的一个controller类的实例化过程
1）spring使用AbstractAutowireCapableBeanFactory工厂创建controller类实例
2）通过doCreateBean方法创建bean：首先创建实例对象，然后方法内调用本类的populateBean方法对内部的依赖bean进行初始化
3）初始化过程中调用了AutowiredAnnotationBeanPostProcessor的postProcessProperties方法
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
//首先获得所有被注解了的需要初始化的成员变量列表
InjectionMetadata metadata = this.findAutowiringMetadata(beanName, bean.getClass(), pvs); try {
metadata.inject(bean, beanName, pvs); return pvs; } catch (BeanCreationException var6) { throw var6; } catch (Throwable var7) { throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", var7); } }
public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable { Collection<InjectionMetadata.InjectedElement> checkedElements = this.checkedElements; Collection<InjectionMetadata.InjectedElement> elementsToIterate = checkedElements != null ? checkedElements : this.injectedElements; InjectionMetadata.InjectedElement element; if (!((Collection)elementsToIterate).isEmpty()) { for(Iterator var6 = ((Collection)elementsToIterate).iterator(); var6.hasNext(); element.inject(target, beanName, pvs)) { element = (InjectionMetadata.InjectedElement)var6.next(); if (logger.isTraceEnabled()) { logger.trace("Processing injected element of bean '" + beanName + "': " + element); } } } }
可以看到，这里具体操作是调用了AutowiredAnnotationBeanPostProcessor的内部类AutowiredFieldElement中重写抽象类InjectedElement的inject方法
private class AutowiredFieldElement extends InjectedElement { private final boolean required; private volatile boolean cached = false; @Nullable private volatile Object cachedFieldValue; public AutowiredFieldElement(Field field, boolean required) { super(field, (PropertyDescriptor)null); this.required = required; } protected void inject(Object bean, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable { Field field = (Field)this.member; Object value; if (this.cached) { value = AutowiredAnnotationBeanPostProcessor.this.resolvedCachedArgument(beanName, this.cachedFieldValue); } else { DependencyDescriptor desc = new DependencyDescriptor(field, this.required); desc.setContainingClass(bean.getClass()); Set<String> autowiredBeanNames = new LinkedHashSet(1); Assert.state(AutowiredAnnotationBeanPostProcessor.this.beanFactory != null, "No BeanFactory available"); TypeConverter typeConverter = AutowiredAnnotationBeanPostProcessor.this.beanFactory.getTypeConverter(); try { value = AutowiredAnnotationBeanPostProcessor.this.beanFactory.resolveDependency(desc, beanName, autowiredBeanNames, typeConverter); } catch (BeansException var12) { throw new UnsatisfiedDependencyException((String)null, beanName, new InjectionPoint(field), var12); } synchronized(this) { if (!this.cached) { if (value == null && !this.required) { this.cachedFieldValue = null; } else { this.cachedFieldValue = desc; AutowiredAnnotationBeanPostProcessor.this.registerDependentBeans(beanName, autowiredBeanNames); if (autowiredBeanNames.size() == 1) { String autowiredBeanName = (String)autowiredBeanNames.iterator().next(); if (AutowiredAnnotationBeanPostProcessor.this.beanFactory.containsBean(autowiredBeanName) && AutowiredAnnotationBeanPostProcessor.this.beanFactory.isTypeMatch(autowiredBeanName, field.getType())) { this.cachedFieldValue = new AutowiredAnnotationBeanPostProcessor.ShortcutDependencyDescriptor(desc, autowiredBeanName, field.getType()); } } } this.cached = true; } } } if (value != null) { ReflectionUtils.makeAccessible(field); field.set(bean, value); } } } }
而抽象类抽象类InjectedElement的inject方法内部的实现其实只是给他的成员变量赋空值，这里调用的是子类重后的方法，方法里再次调用beanFactory创建需要赋值的成员变量实例。
所以算是递归调用beanfactory创建需要的所有bean。
