源码解析SpringMVC处理请求的完整流程

1.WebMvcAutoConfiguration

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EnableWebMvcConfiguration自动装配类负责加载SpringMVC涉及的HandlerAdapter、HandlerMapping、ExceptionHandlerExceptionResolver等。
SpringMVC利用 DispatchServlet 处理上游Tomcat的请求时，会被HandlerMapping、HandlerAdapter的相关子类分别先后执行，这样做的原因是：

通过RequestUril找到相应的handler是因为HandlerMapping提前建立了 RequestUril & Handler 之间的映射关系。
不同HandlerMapping表明解析Handler上的Uri方式是不同的。
HandlerAdapter触发执行 Uri 在Handler中的目标方法。

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WebMvcAutoConfigurationAdapter自动装配类负责加载SpringMVC涉及的静态资源等Web资源。例如LocaleResolver、视图解析器InternalResourceViewResolver、ContentNegotiatingViewResolver等。

@Configuration(proxyBeanMethods = false)
public class WebMvcAutoConfiguration {private static final String[] SERVLET_LOCATIONS = { "/" };@Configuration(proxyBeanMethods = false)@Import(EnableWebMvcConfiguration.class)@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })@Order(0)public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {...@Bean@ConditionalOnBean(ViewResolver.class)@ConditionalOnMissingBean(name = "viewResolver", value = ContentNegotiatingViewResolver.class)public ContentNegotiatingViewResolver viewResolver(BeanFactory beanFactory) {...}...}// 该注解保证父类WebMvcConfigurationSupport也参与SpringBoot启动过程中各个注解的解析过程@Configuration(proxyBeanMethods = false)public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {...@Bean@Overridepublic RequestMappingHandlerAdapter requestMappingHandlerAdapter(@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager m,@Qualifier("mvcConversionService") FormattingConversionService c,@Qualifier("mvcValidator") Validator v) {RequestMappingHandlerAdapter adapter = super.requestMappingHandlerAdapter(m,c, v);boolean ignoreDefaultModelOnRedirect = this.mvcProperties.isIgnoreDefaultModelOnRedirect();adapter.setIgnoreDefaultModelOnRedirect(this.mvcProperties == null || ignoreDefaultModelOnRedirect);return adapter;}...@Bean@Primary@Overridepublic RequestMappingHandlerMapping requestMappingHandlerMapping(@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager manager,@Qualifier("mvcConversionService") FormattingConversionService conversionService,@Qualifier("mvcResourceUrlProvider") ResourceUrlProvider resourceUrlProvider) {// 调用父类WebMvcConfigurationSupportreturn super.requestMappingHandlerMapping(manager, conversionService,resourceUrlProvider);}...}
}

1.2.WebMvcConfigurationSupport

public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {@Beanpublic RequestMappingHandlerMapping requestMappingHandlerMapping(...}@Beanpublic PathMatcher mvcPathMatcher() {...}@Beanpublic BeanNameUrlHandlerMapping beanNameHandlerMapping(...}@Beanpublic HandlerExceptionResolver handlerExceptionResolver(@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager) {List<HandlerExceptionResolver> exceptionResolvers = new ArrayList<>();configureHandlerExceptionResolvers(exceptionResolvers);if (exceptionResolvers.isEmpty()) {addDefaultHandlerExceptionResolvers(exceptionResolvers, contentNegotiationManager);}