springboot启动源码解析

执行流程图源文件：https://www.processon.com/view/link/5b825917e4b0d4d65be7066a

springboot版本为2.0.7

@SpringBootApplication启动类

@SpringBootApplication
public class StartBootTestApplication {
    public static void main(String[] args) {
        //第一个参数为Spring容器配置类，第二个参数为命令行参数
        SpringApplication.run(StartBootTestApplication.class,args);
    }
}

this.webApplicationType = WebApplicationType.deduceFromClasspath();

WebApplicationType是选择服务的启动类型通过他可以选择性的嵌入不同的服务器
有三种类型：
1.NONE：这个应用不能用作web应用 而且不能使用内置的web服务器服务
2.SERVLET：这个应用用以web应用并且使用内置的web服务器
3.REACTIVE：应用程序应该作为反应性web应用程序运行，并且应该启动嵌入式反应性web服务器

this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
加载所有初始化器，
上下文前置处理prepareContext会触发

this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));

初始化ApplicationListener类型的监听器
上下文刷新refreshContext会触发

/**
*SpringApplication
*/
//构造器初始化
public SpringApplication(ResourceLoader resourceLoader, Class... primarySources) {
this.sources = new LinkedHashSet();
//横幅模式 OFF,CONSOLE,LOG;
this.bannerMode = Mode.CONSOLE;
this.logStartupInfo = true;
this.addCommandLineProperties = true;
this.addConversionService = true;
this.headless = true;
this.registerShutdownHook = true;
this.additionalProfiles = new HashSet();
this.isCustomEnvironment = false;
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet(Arrays.asList(primarySources));
//应用类型NONE,SERVLET,REACTIVE;存在DispatcherHandler，不存在DispatcherServlet，ServletContainer，则为REACTIVE
//不存在javax.servlet.Servlet", "org.springframework.web.context.ConfigurableWebApplicationContext，则为NONE，则为SERVLET

this.webApplicationType = WebApplicationType.deduceFromClasspath();
//spring.factories文件中org.springframework.context.ApplicationContextInitializer=
//org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,
//org.springframework.boot.context.ContextIdApplicationContextInitializer,
//org.springframework.boot.context.config.DelegatingApplicationContextInitializer,
//org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer
this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
//org.springframework.context.ApplicationListener=
//org.springframework.boot.ClearCachesApplicationListener,
//org.springframework.boot.builder.ParentContextCloserApplicationListener,
//org.springframework.boot.context.FileEncodingApplicationListener,
//org.springframework.boot.context.config.AnsiOutputApplicationListener,
//org.springframework.boot.context.config.ConfigFileApplicationListener,
//org.springframework.boot.context.config.DelegatingApplicationListener,
//org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,
//org.springframework.boot.context.logging.LoggingApplicationListener,
//org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener 进行初始化
this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
//推论出主类main
this.mainApplicationClass = this.deduceMainApplicationClass();
}

 spring启动开始，执行run

SpringApplicationRunListeners listeners = this.getRunListeners(args);

SpringApplicationRunListeners 初始化准备事件体系（观察者模式）

//核心开始运行
public ConfigurableApplicationContext run(String... args) {
//秒表，用于记录启动时间，记录每个任务 的时间，
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//spring应用上下文，spring容器
ConfigurableApplicationContext context = null;
//自定义SpringApplication启动错误的回调接口
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
//java.awt.headless模式 默认为true开启
this.configureHeadlessProperty();
//开启监听
//org.springframework.boot.SpringApplicationRunListener=
//org.springframework.boot.context.event.EventPublishingRunListener
SpringApplicationRunListeners listeners = this.getRunListeners(args);
//
listeners.starting();
try {
//参数封装，在命令行下启动应用带的参数，如--server.port
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
//环境准备 1.加载外部化配置的资源到environment 2.触发ApplicationEnvironmentPreparedEvent事件
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
//配置系统属性spring.beaninfo.ignore
this.configureIgnoreBeanInfo(environment);
//打印横幅
Banner printedBanner = this.printBanner(environment);
//创建ApplicationContext 根据webApplicationType
//SERVLET:
// contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext");
//REACTIVE:
// contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext");
// default:
// contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext");
/**
*AnnotationConfigServletWebServerApplicationContext层级关系-》ServletWebServerApplicationContext-》GenericWebApplicationContext
*-》GenericApplicationContext-》AbstractApplicationContext
*/
//部分属性：reader、scanner、beanFactory进行了实例化
context = this.createApplicationContext();
//实例化 用来支持报告关于启动的错误
//# Error Reporters
//org.springframework.boot.SpringBootExceptionReporter=
//org.springframework.boot.diagnostics.FailureAnalyzers
exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
//ApplicationContext准备 加载
this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
//核心：
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);
}
}

//环境准备
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) {
//创建环境 SERVLET StandardServletEnvironment； REACTIVE StandardReactiveWebEnvironment； StandardEnvironment
ConfigurableEnvironment environment = this.getOrCreateEnvironment();
this.configureEnvironment((ConfigurableEnvironment)environment, applicationArguments.getSourceArgs());
listeners.environmentPrepared((ConfigurableEnvironment)environment);
this.bindToSpringApplication((ConfigurableEnvironment)environment);
if (!this.isCustomEnvironment) {
environment = (new EnvironmentConverter(this.getClassLoader())).convertEnvironmentIfNecessary((ConfigurableEnvironment)environment, this.deduceEnvironmentClass());
}

ConfigurationPropertySources.attach((Environment)environment);
return (ConfigurableEnvironment)environment;
}

//ApplicationContext准备 加载
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
//设置上下文的environment
context.setEnvironment(environment);
//应用上下文后处理
this.postProcessApplicationContext(context);
//在context refresh之前，对其应用ApplicationContextInitializer
this.applyInitializers(context);
//上下文准备（目前是空实现，有待扩展）
listeners.contextPrepared(context);
//打印启动日志和启动应用profile
if (this.logStartupInfo) {
this.logStartupInfo(context.getParent() == null);
this.logStartupProfileInfo(context);
}
//向beanFactory注册单例bean：命令行参数bean
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
if (printedBanner != null) {
//向beanFactory注册单例bean：banner bean 
beanFactory.registerSingleton("springBootBanner", printedBanner);
}

if (beanFactory instanceof DefaultListableBeanFactory) {
((DefaultListableBeanFactory)beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}

Set<Object> sources = this.getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
//把bean加载到应用上下文中
this.load(context, sources.toArray(new Object[0]));
//向上下文中添加applicationListener,并广播ApplicationPerpareEvent事件
listeners.contextLoaded(context);
}    

/**
*AbstractApplicationContext
*/ 
//刷新
public void refresh() throws BeansException, IllegalStateException {
Object var1 = this.startupShutdownMonitor;
synchronized(this.startupShutdownMonitor) {
//1.刷新前准备 校验
this.prepareRefresh();
//2.获取DefaultListableBeanFactory实例
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
//3.beanFactory加载配置
this.prepareBeanFactory(beanFactory);

try {
//4.BeanFactory准备工作完成后进行的后置准备工作
//beanFactory后置处理，重写ApplicationContext的postProcessBeanFactory方法 未做处理
this.postProcessBeanFactory(beanFactory);
/********以上是BeanFactory的创建及预准备工作********/

//核心：执行BeanFactoryPostProcessor的方法：
//BeanFactoryPostProcessor:BeanFactory的后置处理器，在BeanFactory标准初始化之后执行的；
//他的重要两个接口：BeanFactoryPostProcessor、BeanDefitionRegistryPostProcessor
this.invokeBeanFactoryPostProcessors(beanFactory);
//注册BeanPostProcessor(Bean的后置处理器)
this.registerBeanPostProcessors(beanFactory);
//7 初始化MessageSource组件（做国际化功能：消息绑定，消息解析）
this.initMessageSource();
//8初始化事件派发器
this.initApplicationEventMulticaster();
//9子类重写这个方法，在容器刷新的时候可以自定义逻辑
this.onRefresh();
//10.给容器中所有项目里面的ApplicationListener注册进来
this.registerListeners();
//11.初始化所有剩下的单实例bean
this.finishBeanFactoryInitialization(beanFactory);
//12.完成beanFactory的初始化创建工作：IOC容器就创建完成
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();
}

}
} 

/**
*AbstractApplicationContext
*/ 
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
//1 设置BeanFactory的类加载器
beanFactory.setBeanClassLoader(this.getClassLoader());
//2 设置支持表达式解析器
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, this.getEnvironment()));
//3 添加部分BeanPostProcessor
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
//4 设置忽略的自动装配的接口EnvironmentAware、EmbeddedValueResolverAware、xxx;
//这些接口的实现类不能通过类型来自动注入
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
//5 注册可以解析的自动装配：我们能直接在任何组件中自动注入：
//BeanFactory/ResourceLoader、ApplicationEventPublisher、ApplicationContext
//使用：
//@Autowired
//BeanFactory beanFactory
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
//6 添加BeanPostProcessor后置处理器
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
//7 添加编译时AspectJ
if (beanFactory.containsBean("loadTimeWeaver")) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
//8 注册组件
if (!beanFactory.containsLocalBean("environment")) {
beanFactory.registerSingleton("environment", this.getEnvironment());
}

if (!beanFactory.containsLocalBean("systemProperties")) {
beanFactory.registerSingleton("systemProperties", this.getEnvironment().getSystemProperties());
}

if (!beanFactory.containsLocalBean("systemEnvironment")) {
beanFactory.registerSingleton("systemEnvironment", this.getEnvironment().getSystemEnvironment());
}

}

/**
*AbstractApplicationContext
*/ 
//执行BeanFactoryPostProcessor的后置处理器方法
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, this.getBeanFactoryPostProcessors());
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean("loadTimeWeaver")) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}

}

/**
*PostProcessorRegistrationDelegate

*/
public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
Set<String> processedBeans = new HashSet();
ArrayList regularPostProcessors;
ArrayList registryProcessors;
int var9;
ArrayList currentRegistryProcessors;
String[] postProcessorNames;
//1.判断beanFactory是否为BeanDefinitionRegistry，beanFactory为DefaultListableBeanFactory，
//而DefaultListableBeanFactory实现了BeanDefinitionRegistry接口
if (beanFactory instanceof BeanDefinitionRegistry) {
//强转成BeanDefinitionRegistry
BeanDefinitionRegistry registry = (BeanDefinitionRegistry)beanFactory;
//保存BeanFactoryPostProcessor类型的后置处理器
regularPostProcessors = new ArrayList();
//保存BeanDefinitionRegistryPostProcessor类型的后置处理器
registryProcessors = new ArrayList();
Iterator var6 = beanFactoryPostProcessors.iterator();
//循环遍历beanFactoryPostProcessors
while(var6.hasNext()) {
BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var6.next();
//判断是否BeanDefinitionRegistryPostProcessor
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
//强转BeanDefinitionRegistryPostProcessor
BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor)postProcessor;
//调用后置方法
registryProcessor.postProcessBeanDefinitionRegistry(registry);
//添加到集合当中
registryProcessors.add(registryProcessor);
} else {
//没有实现BeanDefinitionRegistryPostProcessor接口，添加到regularPostProcessors集合中
regularPostProcessors.add(postProcessor);
}
}
//定义一个集合保存当前准备创建的BeanDefinitionRegistryPostProcessor
currentRegistryProcessors = new ArrayList();
//第一步：去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
String[] var16 = postProcessorNames;
var9 = postProcessorNames.length;

int var10;
String ppName;
//循环遍历获取BeanDefinitionRegistryPostProcessor的类型名称
for(var10 = 0; var10 < var9; ++var10) {
ppName = var16[var10];
//判断是否实现了PriorityOrdered接口
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
//调用getBean方法获取该对象加入currentRegistryProcessors集合中
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
//同时加入processedBeans集合中
processedBeans.add(ppName);
}
}
//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
//保存到registryProcessors中
registryProcessors.addAll(currentRegistryProcessors);
/**
*核心：典型的BeanDefinitionRegistryPostProcessor是ConfigurationClassPostProcessor
*用于进行bean定义的加载 ->processConfigBeanDefinitions方法
*/
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
//1清除当前临时集合currentRegistryProcessors
currentRegistryProcessors.clear();
//又在容器中获取BeanDefinitionRegistryPostProcessor的bean处理器名称
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
var16 = postProcessorNames;
var9 = postProcessorNames.length;

for(var10 = 0; var10 < var9; ++var10) {
ppName = var16[var10];
//没被处理过 且实现了Ordered接口
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
//调用getBean方法获取该对象加入currentRegistryProcessors集合中
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
//同时加入processedBeans集合中
processedBeans.add(ppName);
}
}
//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
//保存到registryProcessors中
registryProcessors.addAll(currentRegistryProcessors);
//调用后置处理方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
//2清除当前临时集合currentRegistryProcessors
currentRegistryProcessors.clear();
boolean reiterate = true;
//调用没有实现任何优先级接口的BeanDefinitionRegistryPostProcessor
while(reiterate) {
//进入循环把reiterate更新为false
reiterate = false;
//在容器中获取BeanDefinitionRegistryPostProcessor的bean处理器名称
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
String[] var19 = postProcessorNames;
var10 = postProcessorNames.length;

for(int var26 = 0; var26 < var10; ++var26) {
String ppName = var19[var26];
//没有被处理过的
if (!processedBeans.contains(ppName)) {
//调用getBean方法获取该对象加入currentRegistryProcessors集合中
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
//同时加入processedBeans集合中
processedBeans.add(ppName);

reiterate = true;
}
}
////对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
//保存到registryProcessors中
registryProcessors.addAll(currentRegistryProcessors);
//调用后置处理方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
//3清除当前临时集合currentRegistryProcessors
currentRegistryProcessors.clear();
}
//调用实现了BeanDefinitionRegistryPostProcessor接口和BeanFactoryPostProcessor接口的方法
invokeBeanFactoryPostProcessors((Collection)registryProcessors, (ConfigurableListableBeanFactory)beanFactory);
//调用实现了BeanFactoryPostProcessor接口的方法
invokeBeanFactoryPostProcessors((Collection)regularPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
} else {
//beanFactory没有实现了BeanDefinitionRegistry 直接调用beanFactoryPostProcessor接口的方法进行后置处理器
invokeBeanFactoryPostProcessors((Collection)beanFactoryPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
}
//最后 获取容器中所有的BeanFactoryPostProcessor
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
//保存实现了priorityOrdered接口
regularPostProcessors = new ArrayList();
//保存实现了Ordered接口
registryProcessors = new ArrayList();
currentRegistryProcessors = new ArrayList();
postProcessorNames = postProcessorNames;//错误代码
int var20 = postProcessorNames.length;

String ppName;
for(var9 = 0; var9 < var20; ++var9) {
ppName = postProcessorNames[var9];
//没被处理过
if (!processedBeans.contains(ppName)) {
//判断是否实现了PriorityOrdered
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
regularPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
//判断是否实现了Ordered
} else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
registryProcessors.add(ppName);
} else {
//没有任何优先级接口
currentRegistryProcessors.add(ppName);
}
}
}

sortPostProcessors(regularPostProcessors, beanFactory);
//先调用BeanFactoryPostProcessor实现了priorityOrdered接口
invokeBeanFactoryPostProcessors((Collection)regularPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList();
Iterator var21 = registryProcessors.iterator();

while(var21.hasNext()) {
String postProcessorName = (String)var21.next();
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
//再调用BeanFactoryPostProcessor实现了Ordered接口
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors((Collection)orderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList();
Iterator var24 = currentRegistryProcessors.iterator();

while(var24.hasNext()) {
ppName = (String)var24.next();
nonOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
//最后调用没有实现任何方法接口
invokeBeanFactoryPostProcessors((Collection)nonOrderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
beanFactory.clearMetadataCache();
}

BeanDefinitionRegistryPostProcessor接口实现类：ConfigurationClassPostProcessor（比较重要）

ConfigurationClassPostProcessor类处理带有@Configuration配置类，使用方法processConfigBeanDefinitions，参照https://www.cnblogs.com/mufeng07/p/12165616.html

ConfigurationClassPostProcessor类解析参照：https://www.cnblogs.com/mufeng07/p/12172549.html