springboot嵌入式Servlet容器自动配置原理

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

    /**
     * 如果容器中有Tomcat.class就使用tomcat容器
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass({ Tomcat.class, UpgradeProtocol.class })
    public static class TomcatWebServerFactoryCustomizerConfiguration {

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

    }

    /**
     * 如果容器中有Jetty
     */
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnClass({ Server.class, Loader.class, WebAppContext.class })
    public static class JettyWebServerFactoryCustomizerConfiguration {

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

    }

    /**
     * 如果容器中有Undertow就加载Undertow
     */
    @Configuration(proxyBeanMethods = false)
    @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(proxyBeanMethods = false)
    @ConditionalOnClass(HttpServer.class)
    public static class NettyWebServerFactoryCustomizerConfiguration {

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

    }

}

springboot-web模块默认依赖tomca，修改内置servlet，引入其他依赖并删除tomcat依赖就可以