1、SpringMVC自动配置概览

Spring Boot provides auto-configuration for Spring MVC that works well with most applications.(大多场景我们都无需自定义配置)
The auto-configuration adds the following features on top of Spring’s defaults:
● Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
----○ 内容协商视图解析器和BeanName视图解析器
● Support for serving static resources, including support for WebJars (covered later in this document)).
---- ○ 静态资源（包括webjars）
● Automatic registration of Converter, GenericConverter, and Formatter beans.
---- ○ 自动注册 Converter，GenericConverter，Formatter
● Support for HttpMessageConverters (covered later in this document).
---- ○ 支持 HttpMessageConverters （后来我们配合内容协商理解原理）
● Automatic registration of MessageCodesResolver (covered later in this document).
---- ○ 自动注册 MessageCodesResolver （国际化用）
● Static index.html support.
---- ○ 静态index.html 页支持
● Custom Favicon support (covered later in this document).
---- ○ 自定义 Favicon
● Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).
---- ○ 自动使用 ConfigurableWebBindingInitializer ，（DataBinder负责将请求数据绑定到JavaBean上）

If you want to keep those Spring Boot MVC customizations and make more MVC customizations (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.
不用@EnableWebMvc注解。使用@Configuration + WebMvcConfigurer 自定义规则

If you want to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or ExceptionHandlerExceptionResolver, and still keep the Spring Boot MVC customizations, you can declare a bean of type WebMvcRegistrations and use it to provide custom instances of those components.
声明WebMvcRegistrations 改变默认底层组件

If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc, or alternatively add your own @Configuration-annotated DelegatingWebMvcConfiguration as described in the Javadoc of @EnableWebMvc.
使用 @EnableWebMvc+@Configuration+DelegatingWebMvcConfiguration 全面接管SpringMVC

2、简单功能分析

建立项目进行测试


创建yaml

2.1、静态资源访问

1、静态资源目录

介绍： 只要静态资源放在下述类路径下：
called /static (or /public or /resources or /META-INF/resources
访问方式： 当前项目根路径/ + 静态资源名
原理： 静态映射/**。
请求进来，先去找Controller看能不能处理。不能处理的所有请求又都交给静态资源处理器。静态资源也找不到则响应404页面

测试，可以访问

如果在controller加入相同路径的请求，则会优先访问controller

2、静态资源访问前缀

拦截器配置方便： 为了拦截动态资源的同时，放行对静态资源的访问，需要为静态资源访问加入特定前缀。
如果不加，拦截/**的时候会把静态资源访问也拦截掉
SpringBoot原始默认无前缀，需要在yaml加入配置

spring:
  mvc:
    static-path-pattern: /res/**

当前项目 + static-path-pattern + 静态资源名 = 静态资源文件夹下找

测试： 必须加上res前缀才能访问静态资源


改变默认的静态资源路径的方法

spring:
  mvc:
    static-path-pattern: /res/**

  resources:
    static-locations: [classpath:/haha]
  ====新版本的SpringBoot需要加Web====
  web:
    resources:
      static-locations: [classpath:/haha]

测试：haha下的2.jpg能访问，public下的1.jpg不行【但是META-INF里的能不知道为啥】

3、webjar

自动映射 /webjars/**

https://www.webjars.org/

        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>jquery</artifactId>
            <version>3.5.1</version>
        </dependency>

访问地址：http://localhost:8080/webjars/jquery/3.5.1/jquery.js 后面地址要按照依赖里面的包路径

2.2、欢迎页支持

● 静态资源路径下 index.html

• 可以配置静态资源路径
• 但是不可以配置静态资源的访问前缀。否则导致 index.html不能被默认访问

● controller能处理/index

测试第一种index.html

spring:
#  mvc:
#    static-path-pattern: /res/**   这个会导致welcome page功能失效

  resources:
    static-locations: [classpath:/haha/]

2.3、自定义 Favicon

favicon.ico 放在静态资源目录下即可。

spring:
#  mvc:
#    static-path-pattern: /res/**   这个会导致 Favicon 功能失效

http://www.atguigu.com/favicon.ico
下载图标,放在haha路径下，同时ctrl+f5刷新网页缓存，就可以看到网页图标

2.4、静态资源配置原理
● SpringBoot启动默认加载 xxxAutoConfiguration 类（自动配置类）
● SpringMVC功能的自动配置类 WebMvcAutoConfiguration，生效

@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
		ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {}

● 给容器中配了什么。

	@Configuration(proxyBeanMethods = false)
	@Import(EnableWebMvcConfiguration.class)
	@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
	@Order(0)
	public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {}

● 配置文件的相关属性和xxx进行了绑定。

WebMvcPropertiesspring.mvc、ResourcePropertiesspring.resources

1、配置类只有一个有参构造器

//有参构造器所有参数的值都会从容器中确定
//ResourceProperties resourceProperties；获取和spring.resources绑定的所有的值的对象【高版本的是WebProperties】
//WebMvcProperties mvcProperties 获取和spring.mvc绑定的所有的值的对象
//ListableBeanFactory beanFactory Spring的beanFactory
//HttpMessageConverters 找到所有的HttpMessageConverters
//ResourceHandlerRegistrationCustomizer 找到 资源处理器的自定义器。=========
//DispatcherServletPath  
//ServletRegistrationBean   给应用注册Servlet、Filter....
	public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,
				ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,
				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
				ObjectProvider<DispatcherServletPath> dispatcherServletPath,
				ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
			this.resourceProperties = resourceProperties;
			this.mvcProperties = mvcProperties;
			this.beanFactory = beanFactory;
			this.messageConvertersProvider = messageConvertersProvider;
			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
			this.dispatcherServletPath = dispatcherServletPath;
			this.servletRegistrations = servletRegistrations;
		}

2、资源处理的默认规则

@Override
		public void addResourceHandlers(ResourceHandlerRegistry registry) {
			if (!this.resourceProperties.isAddMappings()) {
				logger.debug("Default resource handling disabled");
				return;
			}
			Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
			CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
			//webjars的规则
            if (!registry.hasMappingForPattern("/webjars/**")) {
				customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
						.addResourceLocations("classpath:/META-INF/resources/webjars/")
						.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
			}
            
            //
			String staticPathPattern = this.mvcProperties.getStaticPathPattern();
			if (!registry.hasMappingForPattern(staticPathPattern)) {
				customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
						.addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
						.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
			}
		}

spring:
#  mvc:
#    static-path-pattern: /res/**

  resources:
    add-mappings: false   禁用所有静态资源规则

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties {

	private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/",
			"classpath:/resources/", "classpath:/static/", "classpath:/public/" };

	/**
	 * Locations of static resources. Defaults to classpath:[/META-INF/resources/,
	 * /resources/, /static/, /public/].
	 */
	private String[] staticLocations = CLASSPATH_RESOURCE_LOCATIONS;

3、欢迎页的处理规则

	HandlerMapping: 处理器映射,是一种核心组件。保存了每一个Handler能处理哪些请求。	

	@Bean
		public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
				FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
			WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(
					new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),
					this.mvcProperties.getStaticPathPattern());
			welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));
			welcomePageHandlerMapping.setCorsConfigurations(getCorsConfigurations());
			return welcomePageHandlerMapping;
		}

	WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,
			ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) {
		if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
            //要用欢迎页功能，必须是/**，2.7.0可以用自定义前缀了
			logger.info("Adding welcome page: " + welcomePage.get());
			setRootViewName("forward:index.html");
		}
		else if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
            // 调用Controller  /index
			logger.info("Adding welcome page template: index");
			setRootViewName("index");
		}
	}

4、favicon
/favicon.ico