Spring Boot----SpringBoot中SpringMVC配置原理

官方文檔

29.1.1 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.
  • 自動配置ViewResolver（視圖解析器：根據方法的返回值獲得視圖對象(View)，視圖對象決定如何渲染（轉發？重定向？））
  • ContentNegotiatingViewResolver組合了所有的視圖解析器
  • 如何定制？我們只需要給容器添加一個視圖解析器，自動回將其組合進來
• Support for serving static resources, including support for WebJars (covered later in this document)).
• Automatic registration of Converter, GenericConverter, and Formatter beans.
  • Converter：轉換器，比如public String test(User user);表單中傳入的數字，true/false等都是文本，這些文本需要映射到User中，需要轉換器，進行類型轉換，將text(數字)-->int/integer，text(true)-->bool
  • Formatter ：格式化，2017/0/101--->Date
• Support for HttpMessageConverters (covered later in this document).
  • HttpMessageConverters：是SpringMVC用來http請求和響應的，比如將User--->json返回
  • HttpMessageConverters是從容器中確定的
• Automatic registration of MessageCodesResolver (covered later in this document).
• Static index.html support.
• Custom Favicon support (covered later in this document).
• Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).

 

Spring Boot擴展 SpringMVC功能

在spring MVC中，我們可以編寫xml來配置我們需要的一些功能，比如攔截器等等。

you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc

我們可以在類型是WebMvcConfigurer的類上使用@Configuration注解，並且實現我們需要的方法；

class MyInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("test");
        return false;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }
}


@Configuration
public class MyMvcConfig implements WebMvcConfigurer{ //不需要實現WebMvcConfigurer了
    @Bean
    public WebMvcConfigurer webMvcConfigurer(){
        WebMvcConfigurer webMvcConfigurer = new WebMvcConfigurer(){
            @Override
            public void addInterceptors(InterceptorRegistry registry) {
                //攔截所有的請求，springboot幫我們已經做好了靜態資源映射，所以我們可以不加excludePathPatterns("/static/**")，但是如果出現被攔截了，那就手動放行
                registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**").excludePathPatterns("/login").excludePathPatterns("/static/**");
            }
        };
        return webMvcConfigurer;
    }
}

測試的時候，直接實現方法也是可以的。所以上面的 MyMvcConfig就不需要實現 WebMvcConfigurer 方法了

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/xx");
    }
}

　　

 

Spring Boot全面接管SpringMVC功能

@EnableWebMvc
@Configuration
public class MyMvcConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    }
}

為什么加上@EnableWebMvc注解后spring mvc就是失效了呢？

1、導入DelegatingWebMvcConfiguration

@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}

2、DelegatingWebMvcConfiguration 繼承了 WebMvcConfigurationSupport 

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {

3、查看 WebMvcAutoConfiguration 源碼

@Configuration
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })

//條件判斷，組件中有沒有WebMvcConfigurationSupport,沒有才自動配置
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
		ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {

　

 

 不需要經過controller

@Configuration
public class MvcConfig implements WebMvcConfigurer {

    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/home").setViewName("home");
        registry.addViewController("/").setViewName("home");
        registry.addViewController("/hello").setViewName("hello");
        registry.addViewController("/login").setViewName("login");
    }

}