跟跟Springboot启动容器，自动装配的过程
Posted 田海超
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------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----
1、运行被@SpringBootApplication修饰的程序入口，执行main方法，调用SpringApplication的静态run方法,返回ConfigurableApplicationContext。
2、在SpringApplication的静态run方法中创建了以启动类为参数的SpringApplication对象并调用了非静态run方法，构造方法和run方法内容如下
1）首先解析SpringApplication构造方法的操作：
public SpringApplication(Class<?>... primarySources) { this((ResourceLoader)null, primarySources); } public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) { this.sources = new LinkedHashSet(); this.bannerMode = Mode.CONSOLE; this.logStartupInfo = true; this.addCommandLineProperties = true; this.addConversionService = true; this.headless = true; // 用来在容器初始化之后，用来优雅停止的 this.registerShutdownHook = true; this.additionalProfiles = new HashSet(); this.isCustomEnvironment = false; this.lazyInitialization = false; this.resourceLoader = resourceLoader; // PrimarySources 启动类class对象 Assert.notNull(primarySources, "PrimarySources must not be null"); this.primarySources = new LinkedHashSet(Arrays.asList(primarySources)); // 判断是否使用servlet容器启动，是否选择内置的servlet容器。SERVLET使用内嵌容器启动 this.webApplicationType = WebApplicationType.deduceFromClasspath(); // 通过读取META-INF/spring.factories配置创建springboot启动的初试化对象 this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
// 初始化监听类 this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class)); this.mainApplicationClass = this.deduceMainApplicationClass(); } private <T> Collection<T> getSpringFactoriesInstances(Class<T> type) { return this.getSpringFactoriesInstances(type, new Class[0]); } private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) { ClassLoader classLoader = this.getClassLoader(); //使用工厂加载类读取spring.factories文件中配置的接口实现类的全限定名list Set<String> names = new LinkedHashSet(SpringFactoriesLoader.loadFactoryNames(type, classLoader)); //使用反射根据全限定名执行构造方法生成对象 List<T> instances = this.createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names); // 根据实现的Ordered接口，实现getOrder返回的int值排序。没有实现这个接口的类不参与排序，原位置不变 AnnotationAwareOrderComparator.sort(instances); return instances; } private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args, Set<String> names) { List<T> instances = new ArrayList(names.size()); Iterator var7 = names.iterator(); while(var7.hasNext()) { String name = (String)var7.next(); try { Class<?> instanceClass = ClassUtils.forName(name, classLoader); Assert.isAssignable(type, instanceClass); //使用反射调用无参构造方法生成对象 Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes); T instance = BeanUtils.instantiateClass(constructor, args); instances.add(instance); } catch (Throwable var12) { throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, var12); } } return instances; }
SpringFactoriesLoader.loadFactoryNames(type, classLoader)源码如下：
public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) { String factoryTypeName = factoryType.getName(); return (List)loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList()); } private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) { MultiValueMap<String, String> result = (MultiValueMap)cache.get(classLoader); if (result != null) { return result; } else { try { Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories"); //底层封装的是LinkedHashMap，并对add方法进行了重写，保证从不同路径下的spring.factories读取到的同一个key都会在不同循环中都放在同一个key的value中，不会发生覆盖 LinkedMultiValueMap result = new LinkedMultiValueMap(); while(urls.hasMoreElements()) { URL url = (URL)urls.nextElement(); UrlResource resource = new UrlResource(url); // PropertiesLoaderUtils，spring的工具类，将配置文件流写入hashTable子类properties实例中--操作过程中只区分了是不是xml文件 Properties properties = PropertiesLoaderUtils.loadProperties(resource); Iterator var6 = properties.entrySet().iterator(); while(var6.hasNext()) { Entry<?, ?> entry = (Entry)var6.next(); String factoryTypeName = ((String)entry.getKey()).trim(); String[] var9 = StringUtils.commaDelimitedListToStringArray((String)entry.getValue()); int var10 = var9.length; for(int var11 = 0; var11 < var10; ++var11) { String factoryImplementationName = var9[var11]; result.add(factoryTypeName, factoryImplementationName.trim()); } } } cache.put(classLoader, result); return result; } catch (IOException var13) { throw new IllegalArgumentException("Unable to load factories from location [META-INF/spring.factories]", var13); } } }
public void add(K key, @Nullable V value) { List<V> values = (List)this.targetMap.computeIfAbsent(key, (k) -> { return new LinkedList(); }); values.add(value); }
public static void fillProperties(Properties props, Resource resource) throws IOException { InputStream is = resource.getInputStream(); try { String filename = resource.getFilename(); if (filename != null && filename.endsWith(".xml")) { props.loadFromXML(is); } else { props.load(is); } } finally { is.close(); } }
根据Ordered接口排序之前
根据Ordered接口排序之后
初始化的监听类：
2）下面来看看非静态run方法中都做了什么：
public ConfigurableApplicationContext run(String... args) { StopWatch stopWatch = new StopWatch();
stopWatch.start(); ConfigurableApplicationContext context = null; Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList(); this.configureHeadlessProperty(); SpringApplicationRunListeners listeners = this.getRunListeners(args); // 启动监听 listeners.starting(); Collection exceptionReporters; try { ApplicationArguments applicationArguments = new DefaultApplicationArguments(args); ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments); this.configureIgnoreBeanInfo(environment); Banner printedBanner = this.printBanner(environment); // 根据构造方法中获得的webApplicationType枚举类型servlet获得ApplicationContext实例org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext
// 这里new了一个DefualtListableFactiory
//详见下方截图 context = this.createApplicationContext(); // 读取spring.factories文件创建bean exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context); // ConfigurableListableBeanFactory beanFactory = context.getBeanFactory(); // 调用构造方法中创建的ApplicationContextInitializer实例重写的initialize方法做初始化操作 this.prepareContext(context, environment, listeners, applicationArguments, printedBanner); // 详见下面方法 this.refreshContext(context); // this.afterRefresh(context, applicationArguments); stopWatch.stop(); if (this.logStartupInfo) { (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch); } listeners.started(context); this.callRunners(context, applicationArguments); } catch (Throwable var10) { this.handleRunFailure(context, var10, exceptionReporters, listeners); throw new IllegalStateException(var10); } try { listeners.running(context); return context; } catch (Throwable var9) { this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null); throw new IllegalStateException(var9); } } private void refreshContext(ConfigurableApplicationContext context) { // 调用context父类AbstractAppliactionContext执行容器初始化bean，自动装配的过程 this.refresh(context); if (this.registerShutdownHook) { try { // context.registerShutdownHook(); } catch (AccessControlException var3) { } } }
这里其实做了很多初始化工作，在java.lang.reflect.Constructor中public T newInstance(Object ... initargs）方法上打断的看可以看到
走到这里，spring容器启动和初始化算是完成了，下面就是容器开始初始化bean，装配bean的过程
我们注意看下，在springContext的refreshContext方法中，除了调用了AbstractApplicationContext.refresh() 方法，委派他去创建和装配bean外，还做了一个操作就是判断了
registerShutdownHook参数，默认是true，程序会执行AbstractApplicationContext.registerShutdownHook();方法
public void registerShutdownHook() { if (this.shutdownHook == null) { this.shutdownHook = new Thread("SpringContextShutdownHook") { public void run() { synchronized(AbstractApplicationContext.this.startupShutdownMonitor) { AbstractApplicationContext.this.doClose(); } } }; // 注册一个shutdownHook线程 ,当进程停止后执行收尾工作，具体可参考https://www.cnblogs.com/maxstack/p/9112711.html Runtime.getRuntime().addShutdownHook(this.shutdownHook); } }
---------具体看下AbstractApplicationContext执行容器操作的内容:---------
public void refresh() throws BeansException, IllegalStateException { synchronized(this.startupShutdownMonitor) { this.prepareRefresh(); // 这里初始化了所有我们希望被spring管理的bean信息，缓存在工厂类中，具体看下方截图obtainFreshBeanFactory的介绍 ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory(); this.prepareBeanFactory(beanFactory); try { // 空方法体，待子类重写 this.postProcessBeanFactory(beanFactory); // 创建指定bean，详情见 this.invokeBeanFactoryPostProcessors(beanFactory); // this.registerBeanPostProcessors(beanFactory); // this.initMessageSource(); // this.initApplicationEventMulticaster(); // this.onRefresh(); // this.registerListeners(); // 这里使用DefaultListableBeanFactory创建非懒加载的bean this.finishBeanFactoryInitialization(beanFactory); // this.finishRefresh(); } catch (BeansException var9) { if (this.logger.isWarnEnabled()) { this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9); } this.destroyBeans(); this.cancelRefresh(var9); throw var9; } finally { this.resetCommonCaches(); } } }
----------下面详解finishBeanFactoryInitialization做的操作：------
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; springboot自动装配