1. Spring MVC auto-configuration

27.1.1 Spring MVC auto-configuration

Spring Boot provides auto-configuration for Spring MVC that works well with most applications.

The auto-configuration adds the following features on top of Spring’s defaults:

Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
Support for serving static resources, including support for WebJars (see below). 靜態資原始檔夾 WebJars
Automatic registration of Converter, GenericConverter, Formatter beans.
Support for HttpMessageConverters (see below).   
Automatic registration of MessageCodesResolver (see below).
Static index.html support.  靜態首頁訪問
Custom Favicon support (see below).
Automatic use of a ConfigurableWebBindingInitializer bean (see below).
If you want to keep Spring Boot MVC features, and you just want to add additional MVC configuration (interceptors, formatters, view controllers etc.) you can add your own @Configuration class of type WebMvcConfigurerAdapter, but without @EnableWebMvc. If you wish to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter or ExceptionHandlerExceptionResolver you can declare a WebMvcRegistrationsAdapter instance providing such components.

If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc.

解析：

Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans

• 自動配置了檢視解析器,根據方法的返回值得到檢視對，檢視物件決定如何渲染
• ContentNegotiatingViewResolver：組合所有的檢視解析器的；
• 如何定製：我們可以自己給容器中新增一個檢視解析器,自動的將其組合進來

載入所有檢視，並獲取最優的那個.
@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 uses all the other view resolvers to locate
   // a view so it should have a high precedence
   resolver.setOrder(Ordered.HIGHEST_PRECEDENCE);
   return resolver;
}

初始化的時候載入了所有檢視解析器
@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);
         }
      }
   }

  定製一個檢視解析器

@SpringBootApplication
public class WebApplication {

   public static void main(String[] args) {
      SpringApplication.run(WebApplication.class, args);
   }




   //定製一個檢視解析器
   @Bean
   public ViewResolver myViewReolver(){
      return new MyViewResolver();
   }

   public static class MyViewResolver implements ViewResolver{

      @Override
      public View resolveViewName(String viewName, Locale locale) throws Exception {
         return null;
      }
   }
}

驗證

Automatic registration of Converter, GenericConverter, Formatter beans

轉換器、通用轉換器、格式化bean的自動註冊。

Converter:將瀏覽器資料封裝到controller對應的方法引數中，比如：public void (User user),這裡使用了反射。

Formatter 格式化器；比如日期格式化

Support for HttpMessageConverters (see below).   可以自己定義。

HttpMessageConverters ：SpringMVC用來轉換Http請求和響應的，比如響應時候將User轉換為Json；

他從容器中載入來，是從容器中確定。所以可以自己定義。

public class HttpMessageConverters implements Iterable<HttpMessageConverter<?>> {

  ........
構造器新增物件
   public HttpMessageConverters(HttpMessageConverter<?>... additionalConverters) {
      this(Arrays.asList(additionalConverters));
   }

Automatic use of a ConfigurableWebBindingInitializer bean (see below).

自動配置web繫結的初始化

2擴充套件SpringMVC（WebMvcConfigurerAdapter）

01實現檢視解析器和攔截器的功能

<mvc:view‐controller path="/hello" view‐name="success"/>
<mvc:interceptors>
    <mvc:interceptor>
        <mvc:mapping path="/hello"/>
        <bean></bean>
    </mvc:interceptor>
</mvc:interceptors>
 

做法

//使用WebMvcConfigurerAdapter可以來擴充套件SpringMVC的功能
//@EnableWebMvc   不要接管SpringMVC
@Configuration
public class MyMvcConfig extends WebMvcConfigurerAdapter {



    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
       // super.addViewControllers(registry);
        //瀏覽器傳送 /success2 請求來到 success
        registry.addViewController("/success2").setViewName("success");
    }

}