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

官方文档

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.
  • 自动配置ViewResolver（视图解析器：根据方法的返回值获得视图对象(View)，视图对象决定如何渲染（转发？重定向？））
  • ContentNegotiatingViewResolver组合了所有的视图解析器
  • 如何定制？我们只需要给容器添加一个视图解析器，自动回将其组合进来
• Support for serving static resources, including support for WebJars (covered later in this document)).
• Automatic registration of Converter, GenericConverter, and Formatter beans.
  • Converter：转换器，比如public String test(User user);表单中传入的数字，true/false等都是文本，这些文本需要映射到User中，需要转换器，进行类型转换，将text(数字)-->int/integer，text(true)-->bool
  • Formatter ：格式化，2017/0/101--->Date
• Support for HttpMessageConverters (covered later in this document).
  • HttpMessageConverters：是SpringMVC用来http请求和响应的，比如将User--->json返回
  • HttpMessageConverters是从容器中确定的
• 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扩展 SpringMVC功能

在spring MVC中，我们可以编写xml来配置我们需要的一些功能，比如拦截器等等。

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

我们可以在类型是WebMvcConfigurer的类上使用@Configuration注解，并且实现我们需要的方法；

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{ //不需要实现WebMvcConfigurer了
    @Bean
    public WebMvcConfigurer webMvcConfigurer(){
        WebMvcConfigurer webMvcConfigurer = new WebMvcConfigurer(){
            @Override
            public void addInterceptors(InterceptorRegistry registry) {
                //拦截所有的请求，springboot帮我们已经做好了静态资源映射，所以我们可以不加excludePathPatterns("/static/**")，但是如果出现被拦截了，那就手动放行
                registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**").excludePathPatterns("/login").excludePathPatterns("/static/**");
            }
        };
        return webMvcConfigurer;
    }
}

测试的时候，直接实现方法也是可以的。所以上面的 MyMvcConfig就不需要实现 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) {
    }
}

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

1、导入DelegatingWebMvcConfiguration

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

2、DelegatingWebMvcConfiguration 继承了 WebMvcConfigurationSupport 

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {

3、查看 WebMvcAutoConfiguration 源码

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

//条件判断，组件中有没有WebMvcConfigurationSupport,没有才自动配置
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
		ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {

　

 不需要经过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");
    }

}