server.port=8081
server.context‐path=/crud
server.tomcat.uri‐encoding=UTF‐8
//通用的Servlet容器设置
server.xxx
//Tomcat的设置
server.tomcat.xxx

@Bean //一定要将这个定制器加入到容器中 嵌入式的Servlet容器定制器
public EmbeddedServletContainerCustomizer embeddedServletContainerCustomizer(){
　　return new EmbeddedServletContainerCustomizer() {
　　　　//定制嵌入式的Servlet容器相关的规则
　　　　@Override
　　　　public void customize(ConfigurableEmbeddedServletContainer container) {
　　　　　　container.setPort(8083);
　　　　}
　　};
}

import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.boot.web.servlet.server.ConfigurableServletWebServerFactory;
import org.springframework.stereotype.Component;
@Component
public class CustomizationBean implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory> {
    @Override
    public void customize(ConfigurableServletWebServerFactory server) {
        server.setPort(9000);
    }
}

@Bean
public ConfigurableServletWebServerFactory webServerFactory() {
    TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
    factory.setPort(9000);
    // factory.setSessionTimeout(10, TimeUnit.MINUTES);  此方法没找到
    factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html"));
    return factory;
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions><!-- 排除掉默认的Tomcat web容器-->
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<!-- 引入jetty容器。jetty 适合长连接的场景-->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId><!--  spring-boot-starter-undertow ，不支持JSP-->
</dependency>

@Configuration
@ConditionalOnWebApplication
@EnableConfigurationProperties(ServerProperties.class)
public class EmbeddedWebServerFactoryCustomizerAutoConfiguration {

    /**
     * Nested configuration if Tomcat is being used.
     */
    @Configuration
    @ConditionalOnClass({ Tomcat.class, UpgradeProtocol.class })
    public static class TomcatWebServerFactoryCustomizerConfiguration {

        @Bean
        public TomcatWebServerFactoryCustomizer tomcatWebServerFactoryCustomizer(
                Environment environment, ServerProperties serverProperties) {
            return new TomcatWebServerFactoryCustomizer(environment, serverProperties);
        }

    }

    /**
     * Nested configuration if Jetty is being used.
     */
    @Configuration
    @ConditionalOnClass({ Server.class, Loader.class, WebAppContext.class })
    public static class JettyWebServerFactoryCustomizerConfiguration {

        @Bean
        public JettyWebServerFactoryCustomizer jettyWebServerFactoryCustomizer(
                Environment environment, ServerProperties serverProperties) {
            return new JettyWebServerFactoryCustomizer(environment, serverProperties);
        }

    }

    /**
     * Nested configuration if Undertow is being used.
     */
    @Configuration
    @ConditionalOnClass({ Undertow.class, SslClientAuthMode.class })
    public static class UndertowWebServerFactoryCustomizerConfiguration {

        @Bean
        public UndertowWebServerFactoryCustomizer undertowWebServerFactoryCustomizer(
                Environment environment, ServerProperties serverProperties) {
            return new UndertowWebServerFactoryCustomizer(environment, serverProperties);
        }

    }

    /**
     * Nested configuration if Netty is being used.
     */
    @Configuration
    @ConditionalOnClass(HttpServer.class)
    public static class NettyWebServerFactoryCustomizerConfiguration {

        @Bean
        public NettyWebServerFactoryCustomizer nettyWebServerFactoryCustomizer(
                Environment environment, ServerProperties serverProperties) {
            return new NettyWebServerFactoryCustomizer(environment, serverProperties);
        }

    }

}

public class TomcatWebServerFactoryCustomizer implements
        WebServerFactoryCustomizer<ConfigurableTomcatWebServerFactory>, Ordered {

    private final Environment environment;

    private final ServerProperties serverProperties;

    public TomcatWebServerFactoryCustomizer(Environment environment,
            ServerProperties serverProperties) {
        this.environment = environment;
        this.serverProperties = serverProperties;
    }

    @Override
    public int getOrder() {
        return 0;
    }

    @Override
    public void customize(ConfigurableTomcatWebServerFactory factory) {
        ServerProperties properties = this.serverProperties;
        ServerProperties.Tomcat tomcatProperties = properties.getTomcat();
        PropertyMapper propertyMapper = PropertyMapper.get();
        propertyMapper.from(tomcatProperties::getBasedir).whenNonNull()
                .to(factory::setBaseDirectory);
        propertyMapper.from(tomcatProperties::getBackgroundProcessorDelay).whenNonNull()
                .as(Duration::getSeconds).as(Long::intValue)
                .to(factory::setBackgroundProcessorDelay);
        customizeRemoteIpValve(factory);
        propertyMapper.from(tomcatProperties::getMaxThreads).when(this::isPositive)
                .to((maxThreads) -> customizeMaxThreads(factory,
                        tomcatProperties.getMaxThreads()));
        propertyMapper.from(tomcatProperties::getMinSpareThreads).when(this::isPositive)
                .to((minSpareThreads) -> customizeMinThreads(factory, minSpareThreads));
        propertyMapper.from(this::determineMaxHttpHeaderSize).whenNonNull()
                .asInt(DataSize::toBytes).when(this::isPositive)
                .to((maxHttpHeaderSize) -> customizeMaxHttpHeaderSize(factory,
                        maxHttpHeaderSize));
        propertyMapper.from(tomcatProperties::getMaxSwallowSize).whenNonNull()
                .asInt(DataSize::toBytes)
                .to((maxSwallowSize) -> customizeMaxSwallowSize(factory, maxSwallowSize));
        propertyMapper.from(tomcatProperties::getMaxHttpPostSize).asInt(DataSize::toBytes)
                .when((maxHttpPostSize) -> maxHttpPostSize != 0)
                .to((maxHttpPostSize) -> customizeMaxHttpPostSize(factory,
                        maxHttpPostSize));
        propertyMapper.from(tomcatProperties::getAccesslog)
                .when(ServerProperties.Tomcat.Accesslog::isEnabled)
                .to((enabled) -> customizeAccessLog(factory));
        propertyMapper.from(tomcatProperties::getUriEncoding).whenNonNull()
                .to(factory::setUriEncoding);
        propertyMapper.from(properties::getConnectionTimeout).whenNonNull()
                .to((connectionTimeout) -> customizeConnectionTimeout(factory,
                        connectionTimeout));
        propertyMapper.from(tomcatProperties::getMaxConnections).when(this::isPositive)
                .to((maxConnections) -> customizeMaxConnections(factory, maxConnections));
        propertyMapper.from(tomcatProperties::getAcceptCount).when(this::isPositive)
                .to((acceptCount) -> customizeAcceptCount(factory, acceptCount));
        customizeStaticResources(factory);
        customizeErrorReportValve(properties.getError(), factory);
    }
。。。。。。
}

@SpringBootApplication
public class SpringBootDemo01Application {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootDemo01Application.class, args);
    }
}

public class SpringApplication {
　　 //在createApplicationContext（）中根据类型classforName()加载 不同类型的  
    public static final String DEFAULT_CONTEXT_CLASS = "org.springframework.context."
            + "annotation.AnnotationConfigApplicationContext";

    public static final String DEFAULT_SERVLET_WEB_CONTEXT_CLASS = "org.springframework.boot."
            + "web.servlet.context.AnnotationConfigServletWebServerApplicationContext";

    public static final String DEFAULT_REACTIVE_WEB_CONTEXT_CLASS = "org.springframework."
            + "boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext";

　　 //run1调用run2
    public static ConfigurableApplicationContext run(Class<?> primarySource,String... args) {
        return run(new Class<?>[] { primarySource }, args);
    }
　　 //run2调用run3
    public static ConfigurableApplicationContext run(Class<?>[] primarySources,String[] args) {
        return new SpringApplication(primarySources).run(args);
    }
    
　　 //run3启动Web服务器
    public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting();
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                    args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners,
                    applicationArguments);
            configureIgnoreBeanInfo(environment);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            exceptionReporters = getSpringFactoriesInstances(
                    SpringBootExceptionReporter.class,
                    new Class[] { ConfigurableApplicationContext.class }, context);
            prepareContext(context, environment, listeners, applicationArguments,
                    printedBanner);
            refreshContext(context);
            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, exceptionReporters, listeners);
            throw new IllegalStateException(ex);
        }

        try {
            listeners.running(context);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }
    
    
    
    protected ConfigurableApplicationContext createApplicationContext() {
        Class<?> contextClass = this.applicationContextClass;
        if (contextClass == null) {
            try {
                switch (this.webApplicationType) {
                case SERVLET:
                    contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
                    break;
                case REACTIVE:
                    contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
                    break;
                default:
                    contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
                }
            }
            catch (ClassNotFoundException ex) {
                throw new IllegalStateException(
                        "Unable create a default ApplicationContext, "
                                + "please specify an ApplicationContextClass",
                        ex);
            }
        }
        return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
    }


    private void refreshContext(ConfigurableApplicationContext context) {
        refresh(context);
        if (this.registerShutdownHook) {
            try {
                context.registerShutdownHook();
            }
            catch (AccessControlException ex) {
                // Not allowed in some environments.
            }
        }
    }
    
    protected void refresh(ApplicationContext applicationContext) {
        Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);
        ((AbstractApplicationContext) applicationContext).refresh();
    }


}

public abstract class AbstractApplicationContext extends DefaultResourceLoader
        implements ConfigurableApplicationContext {
        
            @Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // 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);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // 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();
            }
        }
    }
    protected void onRefresh() throws BeansException {
        // For subclasses: do nothing by default.
    }
    
}

public class ServletWebServerApplicationContext extends GenericWebApplicationContext
        implements ConfigurableWebServerApplicationContext {
        
    @Override
    protected void onRefresh() {
        super.onRefresh();
        try {
            createWebServer();
        }
        catch (Throwable ex) {
            throw new ApplicationContextException("Unable to start web server", ex);
        }
    }
    
    
    private void createWebServer() {
        WebServer webServer = this.webServer;
        ServletContext servletContext = getServletContext();
        if (webServer == null && servletContext == null) {
            ServletWebServerFactory factory = getWebServerFactory();
            this.webServer = factory.getWebServer(getSelfInitializer());
        }
        else if (servletContext != null) {
            try {
                getSelfInitializer().onStartup(servletContext);
            }
            catch (ServletException ex) {
                throw new ApplicationContextException("Cannot initialize servlet context",
                        ex);
            }
        }
        initPropertySources();
    }
        
}