Spring boot整合tomcat底层原理剖析

// full模式
@Configuration(proxyBeanMethods = false)

// 配置类解析顺序
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)

// 条件注解：表示项目依赖中要有ServletRequest类（server api）
@ConditionalOnClass(ServletRequest.class)
// 表示项目应用类型得是SpringMVC（在启动过程中获取的SpringBoot应用类型）
@ConditionalOnWebApplication(type = Type.SERVLET)

// 读取server下的配置文件
@EnableConfigurationProperties(ServerProperties.class)

// import具体的加载配置的类和具体web实现容器
@Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
		ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,
		ServletWebServerFactoryConfiguration.EmbeddedJetty.class,
		ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
public class ServletWebServerFactoryAutoConfiguration {
	......
}

@Configuration(proxyBeanMethods = false)
// tomcat内部的类，肯定都存在
@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })

// 程序员如果自定义了ServletWebServerFactory的Bean，那么这个Bean就不加载。
@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
static class EmbeddedTomcat {
    @Bean
    TomcatServletWebServerFactory tomcatServletWebServerFactory(
        ObjectProvider<TomcatConnectorCustomizer> connectorCustomizers,
        ObjectProvider<TomcatContextCustomizer> contextCustomizers,
        ObjectProvider<TomcatProtocolHandlerCustomizer<?>> protocolHandlerCustomizers) {
            TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
            // orderedStream()调用时会去Spring容器中找到TomcatConnectorCustomizer类型的Bean，默认是没有的，程序员可以自己定义。这个Bean可以设置一些tomcat的配置，比如端口、协议...
            // TomcatConnectorCustomizer：是用来配置Tomcat中的Connector组件的
            factory.getTomcatConnectorCustomizers().addAll(connectorCustomizers.orderedStream().collect(Collectors.toList()));
            // TomcatContextCustomizer：是用来配置Tomcat中的Context组件的
            factory.getTomcatContextCustomizers().addAll(contextCustomizers.orderedStream().collect(Collectors.toList()));
            // TomcatProtocolHandlerCustomizer：是用来配置Tomcat中的ProtocolHandler组件的
            factory.getTomcatProtocolHandlerCustomizers().addAll(protocolHandlerCustomizers.orderedStream().collect(Collectors.toList()));
            return factory;
        }
    }
}

public WebServer getWebServer(ServletContextInitializer... initializers) {
    if (this.disableMBeanRegistry) {
        Registry.disableRegistry();
    }
    // 构建tomcat对象
    Tomcat tomcat = new Tomcat();

    // 设置相关的属性
    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);
    tomcat.getHost().setAutoDeploy(false);
    configureEngine(tomcat.getEngine());
    for (Connector additionalConnector : this.additionalTomcatConnectors) {
        tomcat.getService().addConnector(additionalConnector);
    }
    prepareContext(tomcat.getHost(), initializers);

    // 启动tomcat，这个方法内部有this.tomcat.start();
    return getTomcatWebServer(tomcat);
}

protected void onRefresh() {
    // 模板方法，先调用它父类的，一般是空方法
    super.onRefresh();
    try {
        // 创建web容器
        createWebServer();
    }
    catch (Throwable ex) {
        throw new ApplicationContextException("Unable to start web server", ex);
    }
}

// 最核心的俩行代码
private void createWebServer() {
    ......
    // 获取web容器，多个或者没有的时候报错
    ServletWebServerFactory factory = getWebServerFactory();

    // 调用这个容器的getWebServer方法，上面的启动tomcat的方法！
    this.webServer = factory.getWebServer(getSelfInitializer());
    ......
}

protected ServletWebServerFactory getWebServerFactory() {
    // Use bean names so that we don't consider the hierarchy

    // 得到所有类型为ServletWebServerFactory的Bean。TomcatServletWebServerFactory、JettyServletWebServerFactory、UndertowServletWebServerFactory都是他得到子类！
    String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class);

    // 不存在，报错
    if (beanNames.length == 0) {
        throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.");
    }

    // 存在不止一个，报错！
    if (beanNames.length > 1) {
        throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple ServletWebServerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames));
    }

    // 返回唯一的一个web容器！
    return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);
}

public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
    // Bean工厂，一个Aware回调进行赋值
    if (this.beanFactory == null) {
        return;
    }
    // 注册webServerFactoryCustomizerBeanPostProcessor这个Bean。
    registerSyntheticBeanIfMissing(registry, "webServerFactoryCustomizerBeanPostProcessor",
        WebServerFactoryCustomizerBeanPostProcessor.class,
        WebServerFactoryCustomizerBeanPostProcessor::new);

    // 注册errorPageRegistrarBeanPostProcessor
    registerSyntheticBeanIfMissing(registry, "errorPageRegistrarBeanPostProcessor",
        ErrorPageRegistrarBeanPostProcessor.class, ErrorPageRegistrarBeanPostProcessor::new);
}

private void postProcessBeforeInitialization(WebServerFactory webServerFactory) {
    // 找到WebServerFactoryCustomizer的Bean
    LambdaSafe.callbacks(WebServerFactoryCustomizer.class, getCustomizers(), webServerFactory)
        // 标记日志用的类
        .withLogger(WebServerFactoryCustomizerBeanPostProcessor.class)
        // 调用customize方法，传入webServerFactory
        .invoke((customizer) -> customizer.customize(webServerFactory));
}

@Override
public void customize(ConfigurableServletWebServerFactory factory) {
    PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
    map.from(this.serverProperties::getPort).to(factory::setPort);
    map.from(this.serverProperties::getAddress).to(factory::setAddress);
    map.from(this.serverProperties.getServlet()::getContextPath).to(factory::setContextPath);
    map.from(this.serverProperties.getServlet()::getApplicationDisplayName).to(factory::setDisplayName);
    map.from(this.serverProperties.getServlet()::isRegisterDefaultServlet).to(factory::setRegisterDefaultServlet);
    map.from(this.serverProperties.getServlet()::getSession).to(factory::setSession);
    map.from(this.serverProperties::getSsl).to(factory::setSsl);
    map.from(this.serverProperties.getServlet()::getJsp).to(factory::setJsp);
    map.from(this.serverProperties::getCompression).to(factory::setCompression);
    map.from(this.serverProperties::getHttp2).to(factory::setHttp2);
    map.from(this.serverProperties::getServerHeader).to(factory::setServerHeader);
    map.from(this.serverProperties.getServlet()::getContextParameters).to(factory::setInitParameters);
    map.from(this.serverProperties.getShutdown()).to(factory::setShutdown);
    for (WebListenerRegistrar registrar : this.webListenerRegistrars) {
        registrar.register(factory);
    }
    if (!CollectionUtils.isEmpty(this.cookieSameSiteSuppliers)) {
        factory.setCookieSameSiteSuppliers(this.cookieSameSiteSuppliers);
    }
}

@Bean
public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(ServerProperties serverProperties, ObjectProvider<WebListenerRegistrar> webListenerRegistrars, ObjectProvider<CookieSameSiteSupplier> cookieSameSiteSuppliers) {
    return new ServletWebServerFactoryCustomizer(serverProperties,webListenerRegistrars.orderedStream().collect(Collectors.toList()),cookieSameSiteSuppliers.orderedStream().collect(Collectors.toList()));
}