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WebMvc自动配置流程讲解

news 2025/8/4 6:31:06

WebMvc自动配置流程讲解

原理分析

启动springMvc内置的视图解析器ContentNegotiatingViewResolver和BeanNameViewResolver
- ContentNegotiatingViewResolver ：并不会解析视图本身，而是委托其他的视图解析器进行解析
  - 所有的视图解析器，都会根据返回的视图名称进行解析视图

@Override
@Nullable
public View resolveViewName(String viewName, Locale locale) throws Exception {RequestAttributes attrs = RequestContextHolder.getRequestAttributes();Assert.state(attrs instanceof ServletRequestAttributes, "No current ServletRequestAttributes");List<MediaType> requestedMediaTypes = getMediaTypes(((ServletRequestAttributes) attrs).getRequest());if (requestedMediaTypes != null) {// 获得所有匹配的视图List<View> candidateViews = getCandidateViews(viewName, locale, requestedMediaTypes);// 获取最终的视图View bestView = getBestView(candidateViews, requestedMediaTypes, attrs);if (bestView != null) {return bestView;}}

委派给其他解析器进行解析

@Override
protected void initServletContext(ServletContext servletContext) {Collection<ViewResolver> matchingBeans =BeanFactoryUtils.beansOfTypeIncludingAncestors(obtainApplicationContext(), ViewResolver.class).values();if (this.viewResolvers == null) {this.viewResolvers = new ArrayList<>(matchingBeans.size());for (ViewResolver viewResolver : matchingBeans) {if (this != viewResolver) {this.viewResolvers.add(viewResolver);}}}

由以上的代码可以得出结论，它是从Spring IOC容器中获得viewResolver，我们可以自己定制一个viewResolver，ContentNegotiatingViewResolver也会帮我们委派解析

BeanNameViewResolver
- 根据handler方法返回的视图名称对应到具体视图并解析（定义一个相同名称的类，此类继承一个view（abstractXlsView等等）的接口去生成一个视图）

支持提供静态资源，包括对WebJars的支持

WebJars将静态资源放在jar包中进行访问

以前要访问jpg、css、js等这些静态资源文件，需要在web.xml配置，在springboot中不需要配置，只需要放到指定的文件夹中就可以读取出来（约定大于配置）

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {if (!this.resourceProperties.isAddMappings()) {logger.debug("Default resource handling disabled");return;}addResourceHandler(registry, "/webjars/**", "classpath:/META-INF/resources/webjars/");addResourceHandler(registry, this.mvcProperties.getStaticPathPattern(), (registration) -> {registration.addResourceLocations(this.resourceProperties.getStaticLocations());if (this.servletContext != null) {ServletContextResource resource = new ServletContextResource(this.servletContext, SERVLET_LOCATION);registration.addResourceLocations(resource);}});
}

为什么我们访问http://localhost:8080/image/timssg.jpg也可以访问到图片呢？

public static class Resources {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;

上述代码表示，当图片位于上面的文件中也是可以被读取出来的

自动注册Converter,GenericConverter和FormatterBean类
支持HttpMessageConverters
- HttpMessageConverters负责http请求和响应的报文处理
自动注册MessageCodesResolver
- 修改错误下的格式转换出错类型转换出错的错误代码

静态index.html支持

在springboot中可以直接返回html的视图
因为在自动WebMvcAutoConfiguration配置类配置
所以就可以通过在配置文件中完成配置

@Bean
@ConditionalOnMissingBean
public InternalResourceViewResolver defaultViewResolver() {InternalResourceViewResolver resolver = new InternalResourceViewResolver();resolver.setPrefix(this.mvcProperties.getView().getPrefix());resolver.setSuffix(this.mvcProperties.getView().getSuffix());return resolver;
}

@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 {/*** The default Spring MVC view prefix.*/public static final String DEFAULT_PREFIX = "";/*** The default Spring MVC view suffix.*/public static final String DEFAULT_SUFFIX = "";