使用WebMvcConfigurationSupport无法访问html页面原因分析

近日在使用

Spring 3.0

+ 无

web.xml

搭建 Spring MVC原型项目时，当使用

spring 5.0

版本以上时，会发现

WebMvcConfigurerAdapter

已经过时，此时将继承

WebMvcConfigurerAdapter

修改为继承

WebMvcConfigurationSupport

后，启动项目将无法访问

html

页面。配置代码如下：

package com.demo3.springmvc.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.*;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration
@EnableWebMvc
@ComponentScan("com.demo3.springmvc")
public class MvcConfig extends WebMvcConfigurationSupport {

@Bean
public InternalResourceViewResolver viewResolver() {
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setPrefix("/WEB-INF/classes/views/");
viewResolver.setSuffix(".html");
return viewResolver;
}

/**
* 访问静态文件
*/
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/assets/**").addResourceLocations("classpath:/assets/");
}

/**
* 建立url与视图映射
*/
@Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/").setViewName("/index");
}

@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
configurer.enable();
}
}

通过以上代码是无法访问html的，然后又将

WebMvcConfigurationSupport

改为

WebMvcConfigurer

(因为

WebMvcConfigurerAdapter

是实现

WebMvcConfigurer

接口)，此时程序可以访问html页面。
后来通过观察

spring api

文档后发现：

This is the main class providing the configuration behind the MVC Java config. It is typically imported by adding

@EnableWebMvc

to an application

@Configuration

class. An alternative more advanced option is to extend directly from this class and override methods as necessary, remembering to add

@Configuration

to the subclass and

@Bean

to overridden

@Bean

methods. For more details see the javadoc of

@EnableWebMvc

.

使用谷歌翻译（没办法，都怪当初英语没好好学，现在只能使用翻译软件了/哭 ）后的大致意思如下：

这是提供MVC Java配置背后配置的主要类。 通常是通过将@EnableWebMvc添加到应用程序@Configuration类中来导入的。 另一种更高级的选择是直接从此类扩展并根据需要重写方法，记住将@Configuration添加到子类中，并记住将@Bean添加到重写的@Bean方法中。 有关更多详细信息，请参见@EnableWebMvc的javadoc。

也就是说，在进行 MVC 配置时，可以使用两种方法：

1. 直接在配置类上添加

   @EnableWebMvc

   并实现

   WebMvcConfigurer

   接口，如：

   package com.demo3.springmvc.config;
   
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.ComponentScan;
   import org.springframework.web.servlet.config.annotation.*;
   import org.springframework.web.servlet.view.InternalResourceViewResolver;
   
   @EnableWebMvc
   @ComponentScan("com.demo3.springmvc")
   public class MvcConfig implements WebMvcConfigurer {
   
   @Bean
   public InternalResourceViewResolver viewResolver() {
   InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
   viewResolver.setPrefix("/WEB-INF/classes/views/");
   viewResolver.setSuffix(".html");
   return viewResolver;
   }
   
   @Override
   public void addResourceHandlers(ResourceHandlerRegistry registry) {
   registry.addResourceHandler("/assets/**").addResourceLocations("classpath:/assets/");
   }
   
   @Override
   public void addViewControllers(ViewControllerRegistry registry) {
   registry.addViewController("/").setViewName("/index");
   }
   
   @Override
   public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
   configurer.enable();
   }
   }

2. 直接继承

   WebMvcConfigurationSupport

   并添加

   @Configuration

   注解

   package com.demo3.springmvc.config;
   
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.ComponentScan;
   import org.springframework.web.servlet.config.annotation.*;
   import org.springframework.web.servlet.view.InternalResourceViewResolver;
   
   @ComponentScan("com.demo3.springmvc")
   public class MvcConfig extends WebMvcConfigurationSupport {
   
   @Bean
   public InternalResourceViewResolver viewResolver() {
   InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
   viewResolver.setPrefix("/WEB-INF/classes/views/");
   viewResolver.setSuffix(".html");
   return viewResolver;
   }
   
   @Override
   public void addResourceHandlers(ResourceHandlerRegistry registry) {
   registry.addResourceHandler("/assets/**").addResourceLocations("classpath:/assets/");
   }
   
   @Override
   public void addViewControllers(ViewControllerRegistry registry) {
   registry.addViewController("/").setViewName("index");
   }
   
   @Override
   public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
   configurer.enable();
   }
   }

   注意： 由于上例使用到了

   @ComponentScan

   ，所以就没再使用

   @Configuration

   注解

参考资料：

1. 《Java EE 开发的颠覆者：Spring Boot实战》 – 汪云飞 编著
2. WebMvcConfigurationSupport class api 文档： https://docs.spring.io/spring-framework/docs/5.1.5.RELEASE/javadoc-api/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupport.html
3. The type WebMvcConfigurerAdapter is deprecated: https://stackoverflow.com/questions/47552835/the-type-webmvcconfigureradapter-is-deprecated
4. Spring mvc请求处理流程详解（一）之视图解析: https://www.geek-share.com/detail/2689770824.html

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