https://www.cnblogs.com/lijinyu08/p/14613902.html
Spring MVC Auto-configuration// Spring Boot为Spring MVC提供了自动配置，它可以很好地与大多数应用程序一起工作。Spring Boot provides auto-configuration for Spring MVC that works well with most applications.// 自动配置在Spring默认设置的基础上添加了以下功能：The auto-configuration adds the following features on top of Spring’s defaults:// 包含视图解析器Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.// 支持静态资源文件夹的路径，以及webjarsSupport for serving static resources, including support for WebJars// 自动注册了Converter：// 转换器，这就是我们网页提交数据到后台自动封装成为对象的东西，比如把"1"字符串自动转换为int类型// Formatter：【格式化器，比如页面给我们了一个2019-8-10，它会给我们自动格式化为Date对象】Automatic registration of Converter, GenericConverter, and Formatter beans.// HttpMessageConverters// SpringMVC用来转换Http请求和响应的的，比如我们要把一个User对象转换为JSON字符串，可以去看官网文档解释；Support for HttpMessageConverters (covered later in this document).// 定义错误代码生成规则的Automatic registration of MessageCodesResolver (covered later in this document).// 首页定制Static index.html support.// 图标定制Custom Favicon support (covered later in this document).// 初始化数据绑定器：帮我们把请求数据绑定到JavaBean中！Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document)./*如果您希望保留Spring Boot MVC功能，并且希望添加其他MVC配置（拦截器、格式化程序、视图控制器和其他功能），则可以添加自己的@configuration类，类型为webmvcconfiguer，但不添加@EnableWebMvc。如果希望提供RequestMappingHandlerMapping、RequestMappingHandlerAdapter或ExceptionHandlerExceptionResolver的自定义实例，则可以声明WebMVCregistrationAdapter实例来提供此类组件。*/If you want to keep Spring Boot MVC features and you want to add additional MVC configuration(interceptors, formatters, view controllers, and other features), you can add your own@Configuration class of type WebMvcConfigurer but without @EnableWebMvc. If you wish to providecustom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, orExceptionHandlerExceptionResolver, you can declare a WebMvcRegistrationsAdapter instance to provide such components.// 如果您想完全控制Spring MVC，可以添加自己的@Configuration，并用@EnableWebMvc进行注释。If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc.
- 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（后续文章有内容协商原理分析）；
- Automatic registration of MessageCodesResolver (covered later in this document).
- 自动注册 MessageCodesResolver （国际化用，少用，一般直接开发两套页面）；
- 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).
即根据方法的返回值取得视图对象（View），然后由视图对象决定如何渲染（转发，重定向）。
我们去看看这里的源码：我们找到 WebMvcAutoConfiguration ， 然后搜索ContentNegotiatingViewResolver。找到如下方法！
@Bean
@ConditionalOnBean(ViewResolver.class)
@ConditionalOnMissingBean(name = "viewResolver", value = ContentNegotiatingViewResolver.class)
public ContentNegotiatingViewResolver viewResolver(BeanFactory beanFactory) {
ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver();
resolver.setContentNegotiationManager(beanFactory.getBean(ContentNegotiationManager.class));
// ContentNegotiatingViewResolver 使用所有其他视图解析器来定位视图，
// 因此它应该具有较高的优先级
resolver.setOrder(Ordered.HIGHEST_PRECEDENCE);
return resolver;
}
我们可以点进这类看看！找到对应的解析视图的代码；
@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) {
// 获取候选的视图对象
List<View> candidateViews = getCandidateViews(viewName, locale, requestedMediaTypes);
// 选择一个最适合的视图对象，然后把这个对象返回
View bestView = getBestView(candidateViews, requestedMediaTypes, attrs);
if (bestView != null) {
return bestView;
}
}
//...
}
我们继续点进去看，他是怎么获得候选的视图的呢？
可以看到，getCandidateViews 中把所有的视图解析器拿来，进行 forEach 循环，挨个解析！
private List<View> getCandidateViews(String viewName, Locale locale, List<MediaType> requestedMediaTypes)
throws Exception {
List<View> candidateViews = new ArrayList<>();
if (this.viewResolvers != null) {
Assert.state(this.contentNegotiationManager != null, "No ContentNegotiationManager set");
for (ViewResolver viewResolver : this.viewResolvers) {
View view = viewResolver.resolveViewName(viewName, locale);
if (view != null) {
candidateViews.add(view);
}
// ...
}
}
if (!CollectionUtils.isEmpty(this.defaultViews)) {
candidateViews.addAll(this.defaultViews);
}
return candidateViews;
}
所以得出结论：ContentNegotiatingViewResolver 这个视图解析器就是用来组合所有的视图解析器的。
我们再去研究下他的组合逻辑，看到有个属性 viewResolvers，看看它是在哪里进行赋值的？
@Override
protected void initServletContext(ServletContext servletContext) {
// 这里它是从beanFactory工具中获取容器中的所有视图解析器
// ViewRescolver.class 把所有的视图解析器来组合的
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);
}
}
}
//...
}
既然它是在容器中去找视图解析器，我们是否可以猜想，我们就可以去实现一个视图解析器了呢？
我们可以自己给容器中去添加一个视图解析器；这个初始化方法就会帮我们自动的将它组合进来！
时间格式化器 - FormattingConversionService
找到格式化转换器：
@Bean
@Override
public FormattingConversionService mvcConversionService() {
Format format = this.mvcProperties.getFormat();
WebConversionService conversionService =
new WebConversionService(new DateTimeFormatters()
.dateFormat(format.getDate())
.timeFormat(format.getTime())
.dateTimeFormat(format.getDateTime()));
addFormatters(conversionService);
return conversionService;
}
可以看到，这里设置的时间格式是从 mvcProperties 属性文件中读取的，即我们可以在 springboot 配置文件中自定义配置的：org.springframework.boot.autoconfigure.web.servlet.WebMvcProperties.Format
spring:
mvc:
format:
date: dd/MM/yyyy
time: HH:mm:ss
date-time: yyyy-MM-dd HH:mm:ss
若有收获，就点个赞吧
0 人点赞
