SpringBoot内嵌容器tomcat、jetty、undertow切换

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今天单独说一下SpringBoot的内嵌容器，我们可以直接启动SpringBoot项目，是因为SpringBoot默认给我们提供了tomcat容器，除了tomcat，SpringBoot还给我们提供了jetty、undertow两种容器选择，我们说一下如何切换使用jetty、undertow容器，首先我们找到源码，看一看

@Configuration(
    proxyBeanMethods = false
)
//首先必须是一个Web应用
@ConditionalOnWebApplication
//会加载我们在application.properties中的自定义配置
@EnableConfigurationProperties({ServerProperties.class})
public class EmbeddedWebServerFactoryCustomizerAutoConfiguration {
    public EmbeddedWebServerFactoryCustomizerAutoConfiguration() {
    }

    @Configuration(
        proxyBeanMethods = false
    )
    @ConditionalOnClass({HttpServer.class})
    public static class NettyWebServerFactoryCustomizerConfiguration {
        public NettyWebServerFactoryCustomizerConfiguration() {
        }

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

    @Configuration(
        proxyBeanMethods = false
    )
    //当Undertow.class、SslClientAuthMode.class存在时生效
    @ConditionalOnClass({Undertow.class, SslClientAuthMode.class})
    public static class UndertowWebServerFactoryCustomizerConfiguration {
        public UndertowWebServerFactoryCustomizerConfiguration() {
        }

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

    @Configuration(
        proxyBeanMethods = false
    )
    //当Server.class、Loader.class、WebAppContext.class存在时生效
    @ConditionalOnClass({Server.class, Loader.class, WebAppContext.class})
    public static class JettyWebServerFactoryCustomizerConfiguration {
        public JettyWebServerFactoryCustomizerConfiguration() {
        }

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

    @Configuration(
        proxyBeanMethods = false
    )
    //当Tomcat.class，UpgradeProtocol.class存在时生效
    @ConditionalOnClass({Tomcat.class, UpgradeProtocol.class})
    public static class TomcatWebServerFactoryCustomizerConfiguration {
        public TomcatWebServerFactoryCustomizerConfiguration() {
        }

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

如果三个容器同时存在，那么他们的优先级是tomcat > jetty > undertow，引入spring-boot-starter-web依赖中就有tomcat容器，所以我们不需要另外引入，如果要使用jetty或者undertow，那么就需要我们单独引入他们的依赖了，这些SpringBoot都给我们默认了版本，所以也不需要再添加版本。

一、pom.xml文件配置
当我们要使用jetty或者undertow时，需要将tomcat容器移除掉，如果jetty和undertow的依赖也同时存在，当我们想使用undertow时，需要将jetty的依赖移除掉，因为jetty的优先级高于undertow，当使用jetty时，undertow的依赖无需移除掉。

<dependencies>
	<dependency>
	    <groupId>org.springframework.bootgroupId>
	    <artifactId>spring-boot-starter-webartifactId>
	    <exclusions>
	        <exclusion>
	            <artifactId>spring-boot-starter-tomcatartifactId>
	            <groupId>org.springframework.bootgroupId>
	        exclusion>
	    exclusions>
	dependency>

    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-jettyartifactId>
    dependency>

    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-undertowartifactId>
    dependency>

    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-testartifactId>
        <scope>testscope>
    dependency>
dependencies>

效果：

三个依赖都存在


移除tomcat，保留jetty和undertow的依赖


移除tomcat和jetty，保留undertow

二、通过编写配置类
编写配置类的方式，可以让我们不用管依赖，但是只能配置一个容器，在配置类配置，没有优先级，如果配置了两个或以上容器，启动时会报错

//代表是配置类
@Configuration
public class AuthServerConfiguration {
    
    //声明为一个组件，才会被容器加载
    @Bean
    public TomcatServletWebServerFactory tomcatServletWebServerFactory(){
        TomcatServletWebServerFactory tomcatServletWebServerFactory = new TomcatServletWebServerFactory();
        tomcatServletWebServerFactory.setPort(8085);//我们可以设置容器的一些属性
        return tomcatServletWebServerFactory;
    }

    //@Bean
    public JettyServletWebServerFactory jettyServletWebServerFactory(){
        JettyServletWebServerFactory jettyServletWebServerFactory = new JettyServletWebServerFactory();
        jettyServletWebServerFactory.setPort(8086);
        return jettyServletWebServerFactory;
    }

    //@Bean
    public UndertowServletWebServerFactory undertowServletWebServerFactory(){
        UndertowServletWebServerFactory undertowServletWebServerFactory = new UndertowServletWebServerFactory();
        undertowServletWebServerFactory.setPort(8087);
        return undertowServletWebServerFactory;
    }

}

效果：

配置tomcat


配置jetty


配置undertow

以上就是SpringBoot切换内嵌容器的两种方式，个人感觉还是通过配置类来切换还是比较灵活的。