在上一章咱们剖析了 SpingBoot 启动流程中实例化 SpingApplication 的过程。
return new SpringApplication(primarySources).run(args);
这篇文章咱么说下 run() 办法开始之后都做了那些事件。
持续往下跟着源码进入到 run() 这个是比拟外围的一个办法了
public ConfigurableApplicationContext run(String... args) {StopWatch stopWatch = new StopWatch();
// 计时器开始
stopWatch.start();
// 创立启动上下文对象
DefaultBootstrapContext bootstrapContext = createBootstrapContext();
ConfigurableApplicationContext context = null;
// 配置 Handless 模式，是在短少显示屏、键盘或鼠标时的系统配置
// 默认为 true
configureHeadlessProperty();
// 获取并启动监听器
SpringApplicationRunListeners listeners = getRunListeners(args);
// 启动监听器
listeners.starting(bootstrapContext, this.mainApplicationClass);
try {ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
// 筹备环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
// 疏忽配置的 bean
configureIgnoreBeanInfo(environment);
// 打印 banner, 就是启动的时候在控制台的 spring 图案
Banner printedBanner = printBanner(environment);
// 创立容器
context = createApplicationContext();
context.setApplicationStartup(this.applicationStartup);
// 筹备利用上下文(spring 容器前置解决)
prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
// 刷新容器
refreshContext(context);
// 刷新容器后的扩大接口(spring 容器后置解决)
afterRefresh(context, applicationArguments);
// 完结计时器并打印，这就是咱们启动后 console 的显示的工夫
stopWatch.stop();
if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}
// 公布监听利用上下文启动实现（收回启动完结事件）listeners.started(context);
// 执行 runner
callRunners(context, applicationArguments);
}
catch (Throwable ex) {
// 异样解决，如果 run 过程产生异样
handleRunFailure(context, ex, listeners);
throw new IllegalStateException(ex);
}
try {
// 监听利用上下文运行中
listeners.running(context);
}
catch (Throwable ex) {handleRunFailure(context, ex, null);
throw new IllegalStateException(ex);
}
// 返回最终构建的容器对象
return context;
}
接下来就对下面的关键步骤一一解释
1. 获取所有的监听器
这段代码咱们比拟相熟了，上一篇咱么具体介绍过，它的次要作用就是去META-INFO/spring.factories 中加载配置 SpringApplicationRunListener 的监听器如下
显然只有一个事件公布监听器类，拿到了 EventPublishingRunListener 启动事件公布监听器，下一步就是开始启动了listeners.starting（）; 咱们往下跟源码看
@Override
public void starting(ConfigurableBootstrapContext bootstrapContext) {
this.initialMulticaster
.multicastEvent(new ApplicationStartingEvent(bootstrapContext, this.application, this.args));
}启动的时候实际上是又创立了一个 ApplicationStartingEvent 对象，其实就是监听利用启动事件。
其中 initialMulticaster是一个SimpleApplicationEventMuticaster
public void multicastEvent(ApplicationEvent event, @Nullable ResolvableType eventType) {ResolvableType type = eventType != null ? eventType : this.resolveDefaultEventType(event);
// 获取线程池，为每个监听事件创立一个线程
Executor executor = this.getTaskExecutor();
// 依据 ApplicationStartingEvent 事件类型找到对应的监听器，并迭代
Iterator var5 = this.getApplicationListeners(event, type).iterator();
while(var5.hasNext()) {ApplicationListener<?> listener = (ApplicationListener)var5.next();
if (executor != null) {
//
executor.execute(() -> {this.invokeListener(listener, event);
});
} else {this.invokeListener(listener, event);
}
}
}2. 筹备环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
DefaultBootstrapContext bootstrapContext, ApplicationArguments applicationArguments) {
// Create and configure the environment
// 这里咱们退出了 web 依赖所以是一个 servlet 容器
ConfigurableEnvironment environment = getOrCreateEnvironment();
// 配置环境
configureEnvironment(environment, applicationArguments.getSourceArgs());
// 环境筹备实现
ConfigurationPropertySources.attach(environment);
listeners.environmentPrepared(bootstrapContext, environment);
DefaultPropertiesPropertySource.moveToEnd(environment);
configureAdditionalProfiles(environment);
bindToSpringApplication(environment);
if (!this.isCustomEnvironment) {environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
ConfigurationPropertySources.attach(environment);
return environment;
}因为咱们是增加了 web 的依赖 getOrCreateEnvironment（）返回的是一个standardservletEnviroment 规范的 servlet 环境
2.1 配置环境
protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {if (this.addConversionService) {
// 嵌入式的转换器
ConversionService conversionService = ApplicationConversionService.getSharedInstance();
environment.setConversionService((ConfigurableConversionService) conversionService);
}
// 配置属性资源文件
configurePropertySources(environment, args);
// 配置文件
configureProfiles(environment, args);
}利用嵌入的转换器ApplicationConversionService
public static void configure(FormatterRegistry registry) {DefaultConversionService.addDefaultConverters(registry);
DefaultFormattingConversionService.addDefaultFormatters(registry);
// 格局转换
addApplicationFormatters(registry);
// 类型转换
addApplicationConverters(registry);
}
=============== 格局转换 =================
public static void addApplicationFormatters(FormatterRegistry registry) {registry.addFormatter(new CharArrayFormatter());
registry.addFormatter(new InetAddressFormatter());
registry.addFormatter(new IsoOffsetFormatter());
}
======================== 类型转换 ===================
public static void addApplicationConverters(ConverterRegistry registry) {addDelimitedStringConverters(registry);
registry.addConverter(new StringToDurationConverter());
registry.addConverter(new DurationToStringConverter());
registry.addConverter(new NumberToDurationConverter());
registry.addConverter(new DurationToNumberConverter());
registry.addConverter(new StringToPeriodConverter());
registry.addConverter(new PeriodToStringConverter());
registry.addConverter(new NumberToPeriodConverter());
registry.addConverter(new StringToDataSizeConverter());
registry.addConverter(new NumberToDataSizeConverter());
registry.addConverter(new StringToFileConverter());
registry.addConverter(new InputStreamSourceToByteArrayConverter());
registry.addConverterFactory(new LenientStringToEnumConverterFactory());
registry.addConverterFactory(new LenientBooleanToEnumConverterFactory());
if (registry instanceof ConversionService) {addApplicationConverters(registry, (ConversionService) registry);
}
}
2.2 环境筹备实现
同下面启动监听事件，这次的环境筹备也是同样的代码
@Override
public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext,
ConfigurableEnvironment environment) {
this.initialMulticaster.multicastEvent(
// 创立一个应用环境筹备事件对象
new ApplicationEnvironmentPreparedEvent(bootstrapContext, this.application, this.args, environment));
}debug 进去之后代码跟 AppLicationstrigevent 事件对象是一样的。不再赘述。
不过这里是 7 个监听器对象
3. 配置疏忽的 bean
configureIgnoreBeanInfo(environment);
4. 打印 banner
这是 SpringBoot 默认的启动时的图标
Banner printedBanner = printBanner(environment);这个是能够自定义的，也能够是图篇或是文本文件中的图形
5. 创立容器
紧接着上一篇，接下来就是创立容器
protected ConfigurableApplicationContext createApplicationContext() {return this.applicationContextFactory.create(this.webApplicationType);
}6. 筹备利用上下文
private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments, Banner printedBanner) {
// 设置环境参数
context.setEnvironment(environment);
// 设置后处理利用上下文
postProcessApplicationContext(context);
// 把从 spring.factories 中加载的 org.springframework.bt.context.ConfigurationwarningsApplicationContextIitiaLizer，进行初始化操作
applyInitializers(context);
//EventPubLishingRunListener 公布利用上下文事件
listeners.contextPrepared(context);
// 打印启动日志
bootstrapContext.close(context);
if (this.logStartupInfo) {logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// Add boot specific singleton beans
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
if (printedBanner != null) {
// 注册一个字是 springAppLicationArguments 单例的 bean
beanFactory.registerSingleton("springBootBanner", printedBanner);
}
if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory)
.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.lazyInitialization) {context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}
// Load the sources 获取所有资源
Set<Object> sources = getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
// 创立 BeanDefinitionLoader 加载器加载注册所有的资源
load(context, sources.toArray(new Object[0]));
// 同之前，公布利用上下文 加载事件
listeners.contextLoaded(context);
}7. 刷新利用上下文
刷新利用上下文就进入了 spring 的源码了
public void refresh() throws BeansException, IllegalStateException {synchronized(this.startupShutdownMonitor) {StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// Prepare this context for refreshing.
// 筹备刷新上下文
this.prepareRefresh();
// Tetl the subclass to refresh the internal bean facto
// 告诉子类刷新外部工厂
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
// 筹备 Bean 工厂
this.prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in contex t subc lasses.
// 容许在上下文子类中对 bean 工厂进行后处理。// Invoke factory processors registered as beans in the context,
this.postProcessBeanFactory(beanFactory);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
this.invokeBeanFactoryPostProcessors(beanFactory);
// 注册后置处理器。this.registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
// 初始化信息源
this.initMessageSource();
// 初始化上下文事件公布器
this.initApplicationEventMulticaster();
// 初始化其余自定义 bean
this.onRefresh();
// 注册监听器
this.registerListeners();
this.finishBeanFactoryInitialization(beanFactory);
// 实现刷新，清缓存，初始化生命周期，事件公布等
this.finishRefresh();} catch (BeansException var10) {if (this.logger.isWarnEnabled()) {this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt:" + var10);
}
// 销毁 bean
this.destroyBeans();
// Reset 'active'flag.
this.cancelRefresh(var10);
throw var10;
} finally {this.resetCommonCaches();
contextRefresh.end();}
}
}刷新的代码有点深，也是在这时创立了 Tomcat 对象，这也是SpringBoot 一键启动web 工程的要害
创立了 Tomcat 对象，并设置参数
@Override
public WebServer getWebServer(ServletContextInitializer... initializers) {if (this.disableMBeanRegistry) {Registry.disableRegistry();
}
Tomcat tomcat = new Tomcat();
File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
tomcat.setBaseDir(baseDir.getAbsolutePath());
Connector connector = new Connector(this.protocol);
connector.setThrowOnFailure(true);
tomcat.getService().addConnector(connector);
customizeConnector(connector);
tomcat.setConnector(connector);
tomcat.getHost().setAutoDeploy(false);
configureEngine(tomcat.getEngine());
for (Connector additionalConnector : this.additionalTomcatConnectors) {tomcat.getService().addConnector(additionalConnector);
}
prepareContext(tomcat.getHost(), initializers);
// 返回 TomcatWebServer 服务
return getTomcatWebServer(tomcat);
}8. 刷新后处理
afterReftesh();// 是个一空实现，留着前期扩大
/**
* Called after the context has been refreshed.
* @param context the application context
* @param args the application arguments
*/
protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) {}9. 公布监听利用启动事件
@Override
public void started(ConfigurableApplicationContext context) {context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context));
AvailabilityChangeEvent.publish(context, LivenessState.CORRECT);
}这里是调用 context.publishEvent（）办法，公布利用启动事件 ApplicationStartedEvent.
10. 执行 Runner
获取所有的 ApplicationRuner 和 CommandLineRunner 来初始化一些参数，callRuner（是一个回调函数)
private void callRunners(ApplicationContext context, ApplicationArguments args) {List<Object> runners = new ArrayList<>();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
for (Object runner : new LinkedHashSet<>(runners)) {if (runner instanceof ApplicationRunner) {callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {callRunner((CommandLineRunner) runner, args);
}
}
}11. 公布上下文筹备实现的事件
listeners.running(context);
@Override
public void running(ConfigurableApplicationContext context) {context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));
AvailabilityChangeEvent.publish(context, ReadinessState.ACCEPTING_TRAFFIC);
}这段代码看上去似成相识，后面有很多相似的代码，不同的是这里上下文筹备实现之后公布了一个 ApplicationReadyEvent 事件，申明一下利用上下文筹备实现。
小结
这篇次要是介绍了 SpringBoot 启动过程中 run（） 的这个过程。从中咱们也能够发现一些十分好的编码习惯，大家能够在日常的工作中从模拟到内化，缓缓变成本人的货色。
如果你最近正在学习 SpringBoot，能够参考我的集体网站：程序员波特，目前曾经更新了 SpringBoot2.x，SpringBoot3.x 的系列学习教程，心愿能够帮忙到你。