SpringMVC源码解析

墨蓝 2023-09-25 17:33 64阅读 0赞

## 一、SpringBoot自动配置MVC ##

### 1.1 ServletWebServerFactoryAutoConfiguration ###

@Configuration(proxyBeanMethods = false)
    //在自动配置中具有最高优先级执行
    @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
    @ConditionalOnClass(ServletRequest.class)
    @ConditionalOnWebApplication(type = Type.SERVLET)
    @EnableConfigurationProperties(ServerProperties.class)
    //导致web注册器和服务器
    @Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
          ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,
          ServletWebServerFactoryConfiguration.EmbeddedJetty.class,
          ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
    public class ServletWebServerFactoryAutoConfiguration {
    复制代码

#### 1.1.1 EmbeddedTomcat（默认web服务器） ####

由条件装配的注解 `@ConditionalOnClass` 可以看到，当前 classpath 下必须有 `Tomcat` 这个类，该配置类才会生效

`spring-boot-starter-web` 中默认导入的是 `Tomcat` 的依赖

@Configuration
    @ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })
    @ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
    public static class EmbeddedTomcat {
    
        @Bean
        public TomcatServletWebServerFactory tomcatServletWebServerFactory() {
            return new TomcatServletWebServerFactory();
        }
    
    }
    复制代码

#### 1.1.2 EmbeddedJetty ####

导入需要有Server和Loader

@Configuration(proxyBeanMethods = false)
    @ConditionalOnClass({ Servlet.class, Server.class, Loader.class, WebAppContext.class })
    @ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
    static class EmbeddedJetty {
    
    }
    复制代码

使用`Jetty`需要先`排除Tomcat`然后`导入Jetty的依赖`

<dependency>  
        <groupId>org.springframework.boot</groupId>  
        <artifactId>spring-boot-starter-web</artifactId>  
        <exclusions>  
            <exclusion>  
                <groupId>org.springframework.boot</groupId>  
                <artifactId>spring-boot-starter-tomcat</artifactId>  
            </exclusion>  
        </exclusions>  
    </dependency>  
    
      
      
    <dependency>  
        <groupId>org.springframework.boot</groupId>  
        <artifactId>spring-boot-starter-jetty</artifactId>  
    </dependency>  
    复制代码

#### 1.1.3 EmbeddedUndertow ####

Undertow它是一个`轻量级Web服务器`，但不像传统的 Web 服务器有容器概念，加载一个 Web 应用可以小于 10MB 内存，它提供了对Servlet3.1的支持(`支持异步`)，对`Web Socket`完全支持，用以满足 Web 应用巨大数量的客户端，它不需要容器,只需通过API即可快速搭建Web服务器

@Configuration(proxyBeanMethods = false)
    @ConditionalOnClass({ Servlet.class, Undertow.class, SslClientAuthMode.class })
    @ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
    static class EmbeddedUndertow {
    }
    复制代码

使用`undertow`也需要先`排除Tomcat`然后`导入undertow的依赖`

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-tomcat</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-undertow</artifactId>
    </dependency>
    
    复制代码

#### 1.1.4 ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar ####

这里会注入两个组件`ErrorPageRegistrarBeanPostProcessor(处理错误页面)`和`WebServerFactoryCustomizerBeanPostProcessor(用于创建Tomcat容器)`

创建详情：[juejin.cn/post/720838…][juejin.cn_post_720838]

public static class BeanPostProcessorsRegistrar implements ImportBeanDefinitionRegistrar, BeanFactoryAware {
    
        // ......
    
        @Override
        public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
                BeanDefinitionRegistry registry) {
            if (this.beanFactory == null) {
                return;
            }
            // 编程式注入组件
            registerSyntheticBeanIfMissing(registry, "webServerFactoryCustomizerBeanPostProcessor",
                    WebServerFactoryCustomizerBeanPostProcessor.class);
            registerSyntheticBeanIfMissing(registry, "errorPageRegistrarBeanPostProcessor",
                    ErrorPageRegistrarBeanPostProcessor.class);
        }
    
        private void registerSyntheticBeanIfMissing(BeanDefinitionRegistry registry, String name, Class<?> beanClass) {
            if (ObjectUtils.isEmpty(this.beanFactory.getBeanNamesForType(beanClass, true, false))) {
                RootBeanDefinition beanDefinition = new RootBeanDefinition(beanClass);
                beanDefinition.setSynthetic(true);
                registry.registerBeanDefinition(name, beanDefinition);
            }
        }
    
    }
    复制代码

![format_png][]

### 1.2 DispatcherServletAutoConfiguration ###

这里注册了MVC的核心组件`DispatcherServlet`

// 最高配置优先级
    @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
    @Configuration
    // Servlet环境下才生效
    @ConditionalOnWebApplication(type = Type.SERVLET)
    @ConditionalOnClass(DispatcherServlet.class)
    @AutoConfigureAfter(ServletWebServerFactoryAutoConfiguration.class)
    public class DispatcherServletAutoConfiguration {
    
        public static final String DEFAULT_DISPATCHER_SERVLET_BEAN_NAME = "dispatcherServlet";
    
        public static final String DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME = "dispatcherServletRegistration";
    
        // 注册DispatcherServlet的配置类
        @Configuration
        @Conditional(DefaultDispatcherServletCondition.class)
        @ConditionalOnClass(ServletRegistration.class)
        // 启用配置文件与Properties的映射
        @EnableConfigurationProperties({ HttpProperties.class, WebMvcProperties.class })
        protected static class DispatcherServletConfiguration {
    
            private final HttpProperties httpProperties;
    
            private final WebMvcProperties webMvcProperties;
    
            public DispatcherServletConfiguration(HttpProperties httpProperties, WebMvcProperties webMvcProperties) {
                this.httpProperties = httpProperties;
                this.webMvcProperties = webMvcProperties

[juejin.cn_post_720838]: https://juejin.cn/post/7208384641190674492
[format_png]: https://img-blog.csdnimg.cn/img_convert/5db7614522cdb04277307bf307cd2479.webp?x-oss-process=image/format,png