目录

一.搭建 SpringBoot 底层机制开发环境

1.pom.xml文件配置

2.springboot主程序MainApp.java

3.启动项目，然后我们准备开始思考

4.开始思考

底层机制分析: 仍然是 我们实现 Spring 容器那一套机制 IO/文件扫描+注解+反射+ 集合+映射集合+映射

二.源码分析: SpringApplication.run()

重点

三.实现 SpringBoot 底层机制 【Tomcat 启动分析 + Spring 容器初始化+Tomcat 如何关联Spring 容器 】

1.实现任务阶段 1- 创建 Tomcat, 并启动

1.1说明: 创建 Tomcat, 并启动

1.2分析+代码实现

2.实现任务阶段 2- 创建 Spring 容器

2.1说明: 创建 Spring 容器

2.2 分析+代码实现

3.实现任务阶段 3- 将 Tomcat 和 Spring 容器关联, 并启动 Spring 容器

3.1 说明: 将 Tomcat 和 Spring 容器关联, 并启动 Spring 容器

3.2 分析+代码实现

3.3debug 一下, 看看是否进行 Spring 容器的初始化工作, 可以看到 ac.refresh() 会将

一.搭建 SpringBoot 底层机制开发环境

1.pom.xml文件配置

org.springframework.bootspring-boot-starter-parent2.5.3org.springframework.bootspring-boot-starter-weborg.apache.tomcattomcat-jasper8.5.75

2.springboot主程序MainApp.java

@SpringBootApplication
public class MainApp {public static void main(String[] args) {ConfigurableApplicationContext ioc =SpringApplication.run(Main.class, args);}

3.启动项目，然后我们准备开始思考

我们发现当我们启动项目的时候tomcat也会直接启动，底层到底发生了什么？ 

4.开始思考

首先先建立一个Dog的文件

之后我们将这个文件config写出来

/*** Created with IntelliJ IDEA.** @Author: 海绵hong* @Date: 2022/11/19/22:55* @Description:标识标识的是一个配置类，充当Spring配置文件/容器的角色* 如果该配置类，如果在springboot扫描的包/子包，会被注入到容器中* 在该类中，可以通过这个注解@Bean来注入其他的主键*/
@Configuration
public class Config {/*** 1. 通过@Bean的方式, 将new出来的Bean对象, 放入到Spring容器* 2. 该bean在Spring容器的name/id 默认就是 方法名* 3. 通过方法名, 可以得到注入到spring容器中的dog对象**/@Beanpublic Dog dog(){return new Dog();}}

底层机制分析: 仍然是 我们实现 Spring 容器那一套机制 IO/文件扫描+注解+反射+ 集合+映射集合+映射

二.源码分析: SpringApplication.run()

package com.hong.springboot;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;/*** @author 韩顺平* @version 1.0*/
@SpringBootApplication
public class MainApp {public static void main(String[] args) {//启动springboot应用程序/项目//提出问题: 当我们执行run方法时，怎么就启动我们的内置的tomcat?//在分析run方法的底层机制的基础上，我们自己尝试实现ConfigurableApplicationContext ioc =SpringApplication.run(MainApp.class, args);/*** 这里我们开始Debug SpringApplication.run()* 1. SpringApplication.java* public static ConfigurableApplicationContext run(Class primarySource, String... args) {* return run(new Class[] { primarySource }, args);* }** 2.SpringApplication.java : 创建返回 ConfigurableApplicationContext对象* public static ConfigurableApplicationContext run(Class[] primarySources, String[] args) {* return new SpringApplication(primarySources).run(args);* }** 3. SpringApplication.java** public ConfigurableApplicationContext run(String... args) {* StopWatch stopWatch = new StopWatch();* stopWatch.start();* DefaultBootstrapContext bootstrapCOntext= createBootstrapContext();* ConfigurableApplicationContext cOntext= null;* configureHeadlessProperty();* SpringApplicationRunListeners listeners = getRunListeners(args);* listeners.starting(bootstrapContext, this.mainApplicationClass);* try {* ApplicationArguments applicatiOnArguments= new DefaultApplicationArguments(args);* ConfigurableEnvironment envirOnment= prepareEnvironment(listeners, bootstrapContext, applicationArguments);* configureIgnoreBeanInfo(environment);* Banner printedBanner = printBanner(environment);* cOntext= createApplicationContext(); //严重分析: 创建容器* context.setApplicationStartup(this.applicationStartup);* prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);* refreshContext(context); //严重分析: 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* afterRefresh(context, applicationArguments);* stopWatch.stop();* if (this.logStartupInfo) {* new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);* }* listeners.started(context);* callRunners(context, applicationArguments);* }* catch (Throwable ex) {* handleRunFailure(context, ex, listeners);* throw new IllegalStateException(ex);* }** try {* listeners.running(context);* }* catch (Throwable ex) {* handleRunFailure(context, ex, null);* throw new IllegalStateException(ex);* }* return context;* }** 4. 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/可以处理servlet* protected ConfigurableApplicationContext createApplicationContext() {* return this.applicationContextFactory.create(this.webApplicationType);* }** 5. ApplicationContextFactory.java** ApplicationContextFactory DEFAULT = (webApplicationType) -> {* try {* switch (webApplicationType) {* case SERVLET://默认是进入到这个分支 ，返回AnnotationConfigServletWebServerApplicationContext容器* return new AnnotationConfigServletWebServerApplicationContext();* case REACTIVE:* return new AnnotationConfigReactiveWebServerApplicationContext();* default:* return new AnnotationConfigApplicationContext();* }* }* catch (Exception ex) {* throw new IllegalStateException("Unable create a default ApplicationContext instance, "* + "you may need a custom ApplicationContextFactory", ex);* }* };** 6. SpringApplication.java* private void refreshContext(ConfigurableApplicationContext context) {* if (this.registerShutdownHook) {* shutdownHook.registerApplicationContext(context);* }* refresh(context); //严重分析，真正执行相关任务* }** 7. SpringApplication.java* protected void refresh(ConfigurableApplicationContext applicationContext) {* applicationContext.refresh();* }*** 8. ServletWebServerApplicationContext.java* @Override* public final void refresh() throws BeansException, IllegalStateException {* try {* super.refresh();//分析这个方法* }* catch (RuntimeException ex) {* WebServer webServer = this.webServer;* if (webServer != null) {* webServer.stop();* }* throw ex;* }* }** 9. AbstractApplicationContext.java** @Override* public void refresh() throws BeansException, IllegalStateException {* synchronized (this.startupShutdownMonitor) {* StartupStep cOntextRefresh= this.applicationStartup.start("spring.context.refresh");** // Prepare this context for refreshing.* prepareRefresh();** // Tell the subclass to refresh the internal bean factory.* ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();** // Prepare the bean factory for use in this context.* prepareBeanFactory(beanFactory);** try {* // Allows post-processing of the bean factory in context subclasses.* postProcessBeanFactory(beanFactory);** StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");* // Invoke factory processors registered as beans in the context.* invokeBeanFactoryPostProcessors(beanFactory);** // Register bean processors that intercept bean creation.* registerBeanPostProcessors(beanFactory);* beanPostProcess.end();** // Initialize message source for this context.* initMessageSource();** // Initialize event multicaster for this context.* initApplicationEventMulticaster();** // Initialize other special beans in specific context subclasses.* onRefresh(); //严重分析，当父类完成通用的工作后，再重新动态绑定机制回到子类** // Check for listener beans and register them.* registerListeners();** // Instantiate all remaining (non-lazy-init) singletons.* finishBeanFactoryInitialization(beanFactory);** // Last step: publish corresponding event.* finishRefresh();* }** catch (BeansException ex) {* if (logger.isWarnEnabled()) {* logger.warn("Exception encountered during context initialization - " +* "cancelling refresh attempt: " + ex);* }** // Destroy already created singletons to avoid dangling resources.* destroyBeans();** // Reset &＃39;active&＃39; flag.* cancelRefresh(ex);** // Propagate exception to caller.* throw ex;* }** finally {* // Reset common introspection caches in Spring&＃39;s core, since we* // might not ever need metadata for singleton beans anymore...* resetCommonCaches();* contextRefresh.end();* }* }* }* 10. ServletWebServerApplicationContext.java* @Override* protected void onRefresh() {* super.onRefresh();* try {* createWebServer();//看到胜利的曙光,创建webserver 可以理解成会创建指定web服务-Tomcat* }* catch (Throwable ex) {* throw new ApplicationContextException("Unable to start web server", ex);* } * }* 11. ServletWebServerApplicationContext.java** private void createWebServer() {* WebServer webServer = this.webServer;* ServletContext servletCOntext= getServletContext();* if (webServer == null && servletCOntext== null) {* StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");* ServletWebServerFactory factory = getWebServerFactory();* createWebServer.tag("factory", factory.getClass().toString());* this.webServer = factory.getWebServer(getSelfInitializer());//严重分析,使用TomcatServletWebServerFactory 创建一个TomcatWebServer* createWebServer.end();* getBeanFactory().registerSingleton("webServerGracefulShutdown",* new WebServerGracefulShutdownLifecycle(this.webServer));* getBeanFactory().registerSingleton("webServerStartStop",* new WebServerStartStopLifecycle(this, this.webServer));* }* else if (servletContext != null) {* try {* getSelfInitializer().onStartup(servletContext);* }* catch (ServletException ex) {* throw new ApplicationContextException("Cannot initialize servlet context", ex);* }* }* initPropertySources(); * }** 12. TomcatServletWebServerFactory.java 会创建Tomcat 并启动Tomcat** @Override* public WebServer getWebServer(ServletContextInitializer... initializers) {* if (this.disableMBeanRegistry) {* Registry.disableRegistry();* }* Tomcat tomcat = new Tomcat();//创建了Tomcat对象* File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");* //做了一系列的设置* 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);* return getTomcatWebServer(tomcat); //严重分析该方法.* }** 13. TomcatServletWebServerFactory.java , 这里做了校验创建 TomcatWebServer* protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {* return new TomcatWebServer(tomcat, getPort() >= 0, getShutdown());* }* 14. TomcatServletWebServerFactory.java* public TomcatWebServer(Tomcat tomcat, boolean autoStart, Shutdown shutdown) {* Assert.notNull(tomcat, "Tomcat Server must not be null");* this.tomcat = tomcat;* this.autoStart = autoStart;* this.gracefulShutdown = (shutdown == Shutdown.GRACEFUL) ? new GracefulShutdown(tomcat) : null;* initialize();//分析这个方法.* }* 15.TomcatServletWebServerFactory.java** private void initialize() throws WebServerException {* logger.info("Tomcat initialized with port(s): " + getPortsDescription(false));* synchronized (this.monitor) {* try {* addInstanceIdToEngineName();** Context cOntext= findContext();* context.addLifecycleListener((event) -> {* if (context.equals(event.getSource()) && Lifecycle.START_EVENT.equals(event.getType())) {* // Remove service connectors so that protocol binding doesn&＃39;t* // happen when the service is started.* removeServiceConnectors();* } * });** // Start the server to trigger initialization listeners* this.tomcat.start(); //启动Tomcat** // We can re-throw failure exception directly in the main thread* rethrowDeferredStartupExceptions();** try {* ContextBindings.bindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());* }* catch (NamingException ex) {* // Naming is not enabled. Continue* }** // Unlike Jetty, all Tomcat threads are daemon threads. We create a* // blocking non-daemon to stop immediate shutdown* startDaemonAwaitThread();* }* catch (Exception ex) {* stopSilently();* destroySilently();* throw new WebServerException("Unable to start embedded Tomcat", ex);* }* }* }*/System.out.println("hello ioc");}
}


重点

就是创建了一个容器，注入了相应的bean，启动了tomcat

三.实现 SpringBoot 底层机制 【Tomcat 启动分析 + Spring 容器初始化+Tomcat 如何关联Spring 容器 】

1.实现任务阶段 1- 创建 Tomcat, 并启动

1.1说明: 创建 Tomcat, 并启动

1.2分析+代码实现

1.修改pom.xml

org.springframework.bootspring-boot-starter-weborg.springframework.bootspring-boot-starter-tomcatorg.apache.tomcat.embedtomcat-embed-core8.5.75

2.SpringApplication.java

public class HongSpringApplication {//这里我们会创建tomcat对象，并关联Spring容器, 并启动public static void run() {try {//创建Tomcat对象 HspTomcatTomcat tomcat = new Tomcat();//设置9090tomcat.setPort(9090);//启动tomcat.start();//等待请求接入System.out.println("======9090====等待请求=====");tomcat.getServer().await();} catch (Exception e) {e.printStackTrace();}}
}

3.MainApp.java

public class HongMainApp {public static void main(String[] args) {//启动HspSpringBoot项目/程序HspSpringApplication.run();}
}

2.实现任务阶段 2- 创建 Spring 容器

2.1说明: 创建 Spring 容器

2.2 分析+代码实现

1.Monster.java , 做一个测试 Bean

public class Monster {
}


2.HiController.java, 作为 Controller

@RestController
public class HiController {@RequestMapping("/hi")public String hi() {return "hi,hong HiController";}
}

3.HongConfig.java , 作为 Spring 的配置文件.

/*** @author 海绵hong* @version 1.0* HspConfig:配置类-作为Spring的配置文件* 这里有一个问题，容器怎么知道要扫描哪些包? =>一会代码会体现** 在配置类可以指定要扫描包: @ComponentScan("com.hong.hongspringboot")*/
@Configuration
@ComponentScan("com.hong.hongspringboot")
public class HongConfig {//注入Bean - monster 对象到Spring容器.@Beanpublic Monster monster() {return new Monster();}
}


4.WebApplicationInitializer.java , 作为 Spring 的容器.

/*** @author 海绵hong* @version 1.0* Initializer： 初始化器*//*** 解读* 1. 创建我们的Spring 容器* 2. 加载/关联Spring容器的配置-按照注解的方式* 3. 完成Spring容器配置的bean的创建, 依赖注入* 4. 创建前端控制器 DispatcherServlet , 并让其持有Spring容器* 5. 当DispatcherServlet 持有容器, 就可以进行分发映射, 请小伙伴回忆我们实现SpringMVC底层机制* 6. 这里onStartup 是Tomcat调用, 并把ServletContext 对象传入*/
public class HspWebApplicationInitializer implements WebApplicationInitializer {@Overridepublic void onStartup(ServletContext servletContext) throws ServletException {System.out.println("startup ....");//加载Spring web application cOnfiguration=> 容器//自己 写过 HongSpringApplicationContextAnnotationConfigWebApplicationContext ac =new AnnotationConfigWebApplicationContext();//在ac中注册 HongConfig.class 配置类ac.register(HongConfig.class);ac.refresh();//完成bean的创建和配置//1. 创建注册非常重要的前端控制器 DispatcherServlet//2. 让DispatcherServlet 持有容器//3. 这样就可以进行映射分发, 回忆一下SpringMvc机制[自己实现过]//HongDispatcherServletDispatcherServlet dispatcherServlet = new DispatcherServlet(ac);//返回了ServletRegistration.Dynamic对象ServletRegistration.Dynamic registration =servletContext.addServlet("app", dispatcherServlet);//当tomcat启动时，加载 dispatcherServletregistration.setLoadOnStartup(1);//拦截请求，并进行分发处理//这里在提示 / 和 /* => 在讲解 java web , 自己去看看.registration.addMapping("/");}
}

3.实现任务阶段 3- 将 Tomcat 和 Spring 容器关联, 并启动 Spring 容器

3.1 说明: 将 Tomcat 和 Spring 容器关联, 并启动 Spring 容器

3.2 分析+代码实现

public class HongSpringApplication {//这里我们会创建tomcat对象，并关联Spring容器, 并启动public static void run() {try {//创建Tomcat对象 HspTomcatTomcat tomcat = new Tomcat();//1. 让tomcat可以将请求转发到spring web容器,因此需要进行关联//2. "/hong" 就是我们的项目的 application context , 就是我们原来配置tomcat时，指定的application context//3. "D:\\hspedu_springboot\\hsp-springboot" 指定项目的目录tomcat.addWebapp("/hong","D:\\hong_springboot\\hong-springboot");//设置9090tomcat.setPort(9090);//启动tomcat.start();//等待请求接入System.out.println("======9090====等待请求=====");tomcat.getServer().await();} catch (Exception e) {e.printStackTrace();}}
}


3.3debug 一下, 看看是否进行 Spring 容器的初始化工作, 可以看到 ac.refresh() 会将

结果：