springboot启动流程

Table of Contents

springboot启动流程

不同版本的源码存在差异

配置类

@SpringbootApplication 上继承 @EnableAutoConfiguration 后者用@Import(AutoConfigurationImportSelector.class)引入此类 此类重写selectImports()接口

public interface ImportSelector {
    String[] selectImports(AnnotationMetadata importingClassMetadata);

    @Nullable
    default Predicate<String> getExclusionFilter() {
        return null;
    }
}

重写，AutoConfigurationEntry 内部的配置类集合

	@Override
	public String[] selectImports(AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return NO_IMPORTS;
		}
		AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(annotationMetadata);
		return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
	}

方法体

	protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return EMPTY_ENTRY;
		}
		// 获取注解属性
		AnnotationAttributes attributes = getAttributes(annotationMetadata);
		// 获取自动配置类
		List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);
		// 去重
		configurations = removeDuplicates(configurations);
		// 需要去除的配置类
		Set<String> exclusions = getExclusions(annotationMetadata, attributes);
		checkExcludedClasses(configurations, exclusions);
		configurations.removeAll(exclusions);
		configurations = getConfigurationClassFilter().filter(configurations);
		fireAutoConfigurationImportEvents(configurations, exclusions);
		return new AutoConfigurationEntry(configurations, exclusions);
	}

从这个方法就可以看出加载的自动配置类是在什么位置

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
		List<String> configurations = ImportCandidates.load(AutoConfiguration.class, getBeanClassLoader())
			.getCandidates();
		Assert.notEmpty(configurations,
				"No auto configuration classes found in "
						+ "META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. If you "
						+ "are using a custom packaging, make sure that file is correct.");
		return configurations;
	}

run

实际就是启动spring

	public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
		return new SpringApplication(primarySources).run(args);
	}

新建springApplication的时候会从 classPath推断web类型

	public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
		this.resourceLoader = resourceLoader;
		Assert.notNull(primarySources, "PrimarySources must not be null");
		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
		// 存在webflux,none,servlet等
		this.webApplicationType = WebApplicationType.deduceFromClasspath();
		this.bootstrapRegistryInitializers = new ArrayList<>(
				getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
		setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
		this.mainApplicationClass = deduceMainApplicationClass();
	}
	```
方法体
```java
	// 这里用到了springboot的事件驱动
	public ConfigurableApplicationContext run(String... args) {
		Startup startup = Startup.create();
		if (this.registerShutdownHook) {
			SpringApplication.shutdownHook.enableShutdownHookAddition();
		}
		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);
			// 输入springboot启动log的，	默认是这个Banner.Mode.CONSOLE;
			Banner printedBanner = printBanner(environment);
			context = createApplicationContext();
			context.setApplicationStartup(this.applicationStartup);
			prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
			// 通过这里会启动 tomact 
			refreshContext(context);
			afterRefresh(context, applicationArguments);
			startup.started();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), startup);
			}
			listeners.started(context, startup.timeTakenToStarted());
			// 这里就是spring为用户自定义的接口调用，ApplicationRunner 和 CommandLineRunner
			callRunners(context, applicationArguments);
		}
		catch (Throwable ex) {
			throw handleRunFailure(context, ex, listeners);
		}
		try {
			if (context.isRunning()) {
				listeners.ready(context, startup.ready());
			}
		}
		catch (Throwable ex) {
			throw handleRunFailure(context, ex, null);
		}
		return context;
	}

tomact启动

注意到WebServer接口实现，所以找寻获取webServer的代码

webserver注意到reshContext(…)

	//聚合方法，所以ervletWebServerApplicationContext 必定继承 ConfigurableApplicationContext
	protected void refresh(ConfigurableApplicationContext applicationContext) {
		applicationContext.refresh();
	}

内部方法

private void createWebServer() {
		WebServer webServer = this.webServer;
		ServletContext servletContext = getServletContext();
		if (webServer == null && servletContext == null) {
			StartupStep createWebServer = getApplicationStartup().start("spring.boot.webserver.create");
			// 这里ServletWebFactory 是接口，tomact servlet存在对应的实现
			ServletWebServerFactory factory = getWebServerFactory();
			createWebServer.tag("factory", factory.getClass().toString());
			// 有点类似工厂方法，这里获取统一的webserver
			this.webServer = factory.getWebServer(getSelfInitializer());
			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();
	}

tomact自身的实现

	@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());
		for (LifecycleListener listener : this.serverLifecycleListeners) {
			tomcat.getServer().addLifecycleListener(listener);
		}
		Connector connector = new Connector(this.protocol);
		connector.setThrowOnFailure(true);
		tomcat.getService().addConnector(connector);
		customizeConnector(connector);
		tomcat.setConnector(connector);
		registerConnectorExecutor(tomcat, connector);
		tomcat.getHost().setAutoDeploy(false);
		configureEngine(tomcat.getEngine());
		for (Connector additionalConnector : this.additionalTomcatConnectors) {
			tomcat.getService().addConnector(additionalConnector);
			registerConnectorExecutor(tomcat, additionalConnector);
		}
		//这里也会 准备上下文吗？
		prepareContext(tomcat.getHost(), initializers);
		return getTomcatWebServer(tomcat);
	}

todo

  • 启动时的prepareContext流程
  • springboot的事件驱动