四，分析Spring Boot底层机制(Tomcat 启动分析+Spring容器初始化+Tomcat如
四，分析Spring Boot底层机制(Tomcat 启动分析+Spring容器初始化+Tomcat如何关联 Spring 容器) 以及个人编写启动 Tomcat@
目录
[*]四，分析Spring Boot底层机制(Tomcat 启动分析+Spring容器初始化+Tomcat如何关联 Spring 容器) 以及个人编写启动 Tomcat
[*]1. 源码分析 Spring Boot是如何启动 Tomcat ，并支持访问 @Controller 的 Debug 流程分析
[*]1.1 源码分析: SpringApplication.run( ) 方法
[*]2. 自己编写实现 Spring Boot 底层机制【Tomcat启动分析 + Spring容器初始化 + Tomcat如何关联 Spring容器】
[*]2.1 实现任务阶段1：创建Tomcat 并启动
[*]2.2 实现任务阶段2：创建Spring容器
[*]2.3 实现任务阶段3：将Tomcat 和 Spring 容器关联，并启动Spring容器
[*]3. 末了：
1. 源码分析 Spring Boot是如何启动 Tomcat ，并支持访问 @Controller 的 Debug 流程分析
进行源码分析，天然是少不了，Debug 的。下面就让我们打上断点 ，Debug起来吧
1.1 源码分析: SpringApplication.run( ) 方法
SpringApplication.run()
DeBugSpringApplication.run(MainApp.class, args); 看看 Spring Boot 是如何启动 Tomcat的 我们的Debug 目的：紧抓一条线，就是看到 tomcat 被启动的代码: 好比 tomcat.start()
[*]SpringApplication.java
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// 这里我们开始 Debug SpringApplication。run()
public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {
return run(new Class[]{primarySource}, args);
}
[*]SpringApplication.java
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public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return (new SpringApplication(primarySources)).run(args);
}3.SpringApplication.java
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public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
DefaultBootstrapContext bootstrapContext = this.createBootstrapContext();
ConfigurableApplicationContext context = null;
this.configureHeadlessProperty();
SpringApplicationRunListeners listeners = this.getRunListeners(args);
listeners.starting(bootstrapContext, this.mainApplicationClass);
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, bootstrapContext, applicationArguments);
this.configureIgnoreBeanInfo(environment);
Banner printedBanner = this.printBanner(environment);
context = this.createApplicationContext();// 特别分析： 创建容器
context.setApplicationStartup(this.applicationStartup);
this.prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
this.refreshContext(context);// 特别分析：刷新应用程序上下文，比如：初始化默认设置/注入相关Bean/启动 tomcat
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, listeners);
throw new IllegalStateException(var10);
}
try {
listeners.running(context);
return context;
} catch (Throwable var9) {
this.handleRunFailure(context, var9, (SpringApplicationRunListeners)null);
throw new IllegalStateException(var9);
}
}
[*]SpringApplication.java : 容器类型很多，会根据你的 this.webApplicationType 创建对应的容器
默认 this.webApplicationType 是 servlet 也就是 web 容器/处置惩罚的 servlet
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protected ConfigurableApplicationContext createApplicationContext() {
return this.applicationContextFactory.create(this.webApplicationType);
}
[*]ApplicationContextFactory.java
默认是进入这个分支 case SERVLET:返回 new AnnotationConfigServletWebServerApplicationContext();
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public interface ApplicationContextFactory {
ApplicationContextFactory DEFAULT = (webApplicationType) -> {
try {
switch(webApplicationType) {
case SERVLET:// 默认是进入这个分支
return new AnnotationConfigServletWebServerApplicationContext();
case REACTIVE:
return new AnnotationConfigReactiveWebServerApplicationContext();
default:
return new AnnotationConfigApplicationContext();
}
} catch (Exception var2) {
throw new IllegalStateException("Unable create a default ApplicationContext instance, you may need a custom ApplicationContextFactory", var2);
}
};
ConfigurableApplicationContext create(WebApplicationType webApplicationType);
static ApplicationContextFactory ofContextClass(Class<? extends ConfigurableApplicationContext> contextClass) {
return of(() -> {
return (ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);
});
}
static ApplicationContextFactory of(Supplier<ConfigurableApplicationContext> supplier) {
return (webApplicationType) -> {
return (ConfigurableApplicationContext)supplier.get();
};
}
}2.1 实现任务阶段1：创建Tomcat 并启动
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private void refreshContext(ConfigurableApplicationContext context) {
if (this.registerShutdownHook) {
shutdownHook.registerApplicationContext(context);
}
this.refresh(context);// 特别分析，真正执行相关任务
}2.2 实现任务阶段2：创建Spring容器
bean 对象。
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protected void refresh(ConfigurableApplicationContext applicationContext) {
applicationContext.refresh();
}bean 对象对应的 config 配置类
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public final void refresh() throws BeansException, IllegalStateException {
try {
super.refresh();// 特别分析这个方法
} catch (RuntimeException var3) {
WebServer webServer = this.webServer;
if (webServer != null) {
webServer.stop();
}
throw var3;
}
}controller 处置惩罚业务哀求的控制器
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public void refresh() throws BeansException, IllegalStateException {
synchronized(this.startupShutdownMonitor) {
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
this.prepareRefresh();
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
this.prepareBeanFactory(beanFactory);
try {
this.postProcessBeanFactory(beanFactory);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
this.invokeBeanFactoryPostProcessors(beanFactory);
this.registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
this.initMessageSource();
this.initApplicationEventMulticaster();
this.onRefresh();// 特别分析，当父类完成通用的工作后，再重新动态绑定机制回到
this.registerListeners();
this.finishBeanFactoryInitialization(beanFactory);
this.finishRefresh();
} catch (BeansException var10) {
if (this.logger.isWarnEnabled()) {
this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var10);
}
this.destroyBeans();
this.cancelRefresh(var10);
throw var10;
} finally {
this.resetCommonCaches();
contextRefresh.end();
}
}
}2.3 实现任务阶段3：将Tomcat 和 Spring 容器关联，并启动Spring容器
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protected void onRefresh() {
super.onRefresh();
try {
this.createWebServer();创建 webServer 可以理解成会创建指定 web服务器-tomcat
} catch (Throwable var2) {
throw new ApplicationContextException("Unable to start web server", var2);
}
}https://img2024.cnblogs.com/blog/3084824/202408/3084824-20240830204437947-1002081214.png
private void createWebServer() {
WebServer webServer = this.webServer;
ServletContext servletContext = this.getServletContext();
if (webServer == null && servletContext == null) {
StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");
ServletWebServerFactory factory = this.getWebServerFactory();
createWebServer.tag("factory", factory.getClass().toString());
this.webServer = factory.getWebServer(new ServletContextInitializer[]{this.getSelfInitializer
()}); // 特别分析，使用 TomcatServletWebServerFactory 创建一个TomcatWEbServer
createWebServer.end();
this.getBeanFactory().registerSingleton("webServerGracefulShutdown", new WebServerGracefulShutdownLifecycle(this.webServer));
this.getBeanFactory().registerSingleton("webServerStartStop", new WebServerStartStopLifecycle(this, this.webServer));
} else if (servletContext != null) {
try {
this.getSelfInitializer().onStartup(servletContext);
} catch (ServletException var5) {
throw new ApplicationContextException("Cannot initialize servlet context", var5);
}
}
this.initPropertySources();
}3. 末了：
“在这个末了的篇章中，我要表达我对每一位读者的感激之情。你们的关注和复兴是我创作的动力源泉，我从你们身上吸取了无尽的灵感与勇气。我会将你们的鼓励留在心底，继承在其他的领域奋斗。感谢你们，我们总会在某个时刻再次相遇。”
https://img2024.cnblogs.com/blog/3084824/202408/3084824-20240830204437973-1681370004.gif
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