目录
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()
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 】
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
3.3debug 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
-
<!-- 导入 springboot 父工程，规定的写法 -->
-
<parent>
-
<groupId>org.springframework.boot
</groupId>
-
<artifactId>spring-boot-starter-parent
</artifactId>
-
<version>2.5.3
</version>
-
</parent>
-
<!-- 导入 web 项目场景启动器,会自动导入和 web 开发相关依赖,非常方便 -->
-
<dependencies>
-
<dependency>
-
<groupId>org.springframework.boot
</groupId>
-
<artifactId>spring-boot-starter-web
</artifactId>
-
</dependency>
-
<dependency>
-
<groupId>org.apache.tomcat
</groupId>
-
<artifactId>tomcat-jasper
</artifactId>
-
<version>8.5.75
</version>
-
</dependency>
-
</dependencies>
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
-
**/
-
@Bean
-
public 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()
1
、
Debug
SpringApplication
.
run
(
MainApp
.
class
, args)
看看
SpringBoot
是如何启动
Tomcat
的
.
2
、我们的
Debug
目标
:
紧抓一条线
,
就是看到
tomcat
被启动的代码
.
比如
tomcat.start()
-
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 'active' flag.
-
* cancelRefresh(ex);
-
*
-
* // Propagate exception to caller.
-
* throw ex;
-
* }
-
*
-
* finally {
-
* // Reset common introspection caches in Spring'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'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
● 代码实现
1.修改pom.xml
-
<dependencies>
-
<dependency>
-
<groupId>org.springframework.boot
</groupId>
-
<artifactId>spring-boot-starter-web
</artifactId>
-
<!--因为我们自己要创建Tomcat对象，并启动,
-
因此我们先排除 内嵌的 spring-boot-starter-tomcat-->
-
<exclusions>
-
<exclusion>
-
<groupId>org.springframework.boot
</groupId>
-
<artifactId>spring-boot-starter-tomcat
</artifactId>
-
</exclusion>
-
</exclusions>
-
</dependency>
-
-
<!--我们指定tomcat版本，引入tomcat依赖/库
-
-
1. 使用指定的tomcat 8.5.75
-
2. 如果我们引入自己指定的tomcat,一定要记住把前面spring-boot-starter-tomcat排除
-
3. 如果你不排除，会出现 GenericServlet Not Found错误提示
-
-->
-
<dependency>
-
<groupId>org.apache.tomcat.embed
</groupId>
-
<artifactId>tomcat-embed-core
</artifactId>
-
<version>8.5.75
</version>
-
</dependency>
-
-
-
-
</dependencies>
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 HspTomcat
-
Tomcat
tomcat
=
new
Tomcat();
-
-
//设置9090
-
tomcat.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
●
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.
-
@Bean
-
public 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 {
-
@Override
-
public
void
onStartup
(ServletContext servletContext)
throws ServletException {
-
-
System.out.println(
"startup ....");
-
//加载Spring web application configuration => 容器
-
//自己 写过 HongSpringApplicationContext
-
AnnotationConfigWebApplicationContext
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]
-
//HongDispatcherServlet
-
DispatcherServlet
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 dispatcherServlet
-
registration.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
●
代码实现
1.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 HspTomcat
-
Tomcat
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9090
-
tomcat.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
HspConfig.class
中配置
Bean
实例化装入到容器中
.
结果：
转载：https://blog.csdn.net/weixin_54107527/article/details/127907297
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