spring-boot-SpringMVC自动配置

浅浅的花香味﹌ 2022-05-10 20:14 174阅读 0赞

### **1.Spring MVC auto-conmfiguration** ###

SpringBoot自动配置好了SpringMVC

以下是SpringBoot对SpringMVC的默认配置：（**WebMvcConfiguration**）

*  Inclusion of `ContentNegotiatingViewResolver` and `BeanNameViewResolver` beans.

a.自动配置了ViewResolver(视图解析器：根据方法的返回值得到视图对象（View),视图对象决定如何渲染（转发？重定向)）

b.`ContentNegotiatingViewResolver:组合所有的视图解析器的；`

源码：

@Override
    	protected void initServletContext(ServletContext servletContext) {
    		Collection<ViewResolver> matchingBeans =
    				BeanFactoryUtils.beansOfTypeIncludingAncestors(getApplicationContext(), ViewResolver.class).values();
    		if (this.viewResolvers == null) {
    			this.viewResolvers = new ArrayList<ViewResolver>(matchingBeans.size());
    			for (ViewResolver viewResolver : matchingBeans) {
    				if (this != viewResolver) {
    					this.viewResolvers.add(viewResolver);
    				}
    			}
    		}

*  从BeanFactoryutils中获取所有的视图解析器，把这个视图解析作为他要组合的所有视图解析器*

*  Support for serving static resources, including support for WebJars (covered [later in this document][])).静态资源文件夹路径  webjars
 *  Automatic registration of `Converter`, `GenericConverter`, and `Formatter` beans.

a.Converter:转换器;public String hello(User user);类型转换使用Converter

b.Formatter:格式化器；日期2017.12.17===Date;

**     c.如何定制：我们可以自己给容器中添加一个视图解析器；自动将其组合起来。**

@Bean
    		@ConditionalOnProperty(prefix = "spring.mvc", name = "date-format")//在文件中配置日期格式的规则
    		public Formatter<Date> dateFormatter() {
    			return new DateFormatter(this.mvcProperties.getDateFormat());//日期格式化组件
    		}

*  Support for `HttpMessageConverters` (covered [later in this document][later in this document 1]).

a.HttpMessageConverters:SpringMVC用来转换Http请求和响应；User===json

b.HttpMessageConverters:是从容器中确定；获取所有的HttpMessageConverters；自己给容器中添

加 HttpMessageConverters ，只需要将自己的组件注册到容器中（@Bean,@Component）

*  Automatic registration of `MessageCodesResolver` (covered [later in this document][later in this document 2]).
 *  Static `index.html` support.  静态首页访问
 *  Custom `Favicon` support (covered [later in this document][later in this document 3]).    favicon.ico
 *  Automatic use of a `ConfigurableWebBindingInitializer` bean (covered [later in this document][later in this document 4]).

我们可以配置一个ConfigurableWebBindingIitalizer来替换默认的;(添加到容器)

初始化WebDataBinder;
    请求数据======javaBean;

**org.springframework.boot.autoconfigure.web:web请求场景；**

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 provide custom instances of `RequestMappingHandlerMapping`, `RequestMappingHandlerAdapter`, or `ExceptionHandlerExceptionResolver`, you can declare a `WebMvcRegistrationsAdapter` instance to provide such components.

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

### 2.扩展SpringMVC ###

之前SpringMVC的配置

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

**编写一个配置类（@Configuration）是WebMvcConfigurerAdater类型；不能标注@EnableWebMvc;**

既保留了所有的自动配置，也能用我们扩展的配置

package com.hbsi.config;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.servlet.LocaleResolver;
    import org.springframework.web.servlet.config.annotation.EnableWebMvc;
    import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
    import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
    import com.hbsi.component.LoginHandlerIntercepter;
    import com.hbsi.component.MyLocaleResovler;
    
    @Configuration
    public class MyMvcConfig extends WebMvcConfigurerAdapter{
       //既保留了所有的自动配置，也能用我们扩展的配置
    	@Override
    	public void addViewControllers(ViewControllerRegistry registry) {
    	//浏览器发送/zch请求到success
    		registry.addViewController("/zch").setViewName("success");
    	}
       //所有的WebMvcConfigurerAdapter组件都会一起使用
    	@Bean //将组件注册在容器
      public WebMvcConfigurerAdapter webMvcConfigurerAdapter() {
    	  WebMvcConfigurerAdapter webMvcConfigurerAdapter = new  WebMvcConfigurerAdapter() {
    		  @Override
    		  public void addViewControllers(ViewControllerRegistry registry) {
    				//浏览器发送/zch请求到success
    					registry.addViewController("/").setViewName("login");
    					registry.addViewController("/index.html").setViewName("login");
    //					registry.addViewController("/main.html").setViewName("dashboard");
    				}
    		  //注册拦截器
    		  @Override
    			public void addInterceptors(InterceptorRegistry registry) {
    			  //静态资源 *.css,*.js
    			  //SpringBoot已经做好了静态资源映射  /**拦截所有
    			  registry.addInterceptor(new LoginHandlerIntercepter()).addPathPatterns("/**")
    			  .excludePathPatterns("/","index.html","/user/login");
    			}
    	  };
    	  return webMvcConfigurerAdapter;
      }
    	
    }

原理：

1).WebMvcAutoConfiguration是SpringMVC的自动配置类

2).在做其他自动配置时会导入；@Import(EnableWebMvcConfiguration.class)

@Configuration
    public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {
      private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
    //从容器中获取所有的WebMvcConfigurer
    @Autowired(required = false)
    public void setConfigurers(List<WebMvcConfigurer> configurers) {
          if (!CollectionUtils.isEmpty(configurers)) {
              this.configurers.addWebMvcConfigurers(configurers);
             //一个参考实现;将所有的WebMvcConfigurer相关配置都来一起调用;
             // public void addViewControllers(ViewControllerRegistry registry) {
              //    for (WebMvcConfigurer delegate : this.delegates) {
              //         delegate.addViewControllers(registry);
       
    
    
    
     //
     // } 
    }
    }  
    }

3)容器中所有的WebMvcConfigurer都会一起使用

4）我们的配置类也会被调用；

效果：SpringMVC的自动配置和我们的扩展配置都会起作用

### **3.全面接管SpringMVC** ###

SpringBoot对SpringMVC的自动配置不需要了，所有都是我们自己的配置；所有的SpringMVC的自动配置失效了

我们需要在配置类中添加@EnableWebMvc即可

//使用WebMvcConfigurerAdapter可以来扩展SpringMVC的功能 
    @EnableWebMvc
    @Configuration publicclassMyMvcConfigextendsWebMvcConfigurerAdapter{
    @Override
        public void addViewControllers(ViewControllerRegistry registry) {
           // super.addViewControllers(registry);
    //浏览器发送 /atguigu 请求来到 success
            registry.addViewController("/atguigu").setViewName("success");
        }
    }

原理：

**为什么@EnableWebMvc自动配置失效了**；

1）@EnableWebMvc的核心

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

2）

@Configuration
     publicclassDelegatingWebMvcConfigurationextendsWebMvcConfigurationSupport{

3）

@Configuration
    @ConditionalOnWebApplication
    @ConditionalOnClass({Servlet.class,DispatcherServlet.class,
     WebMvcConfigurerAdapter.class })
     //容器中没有这个组件的时候，这个自动配置类才生效
     @ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
     @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE+10)
     @AutoConfigureAfter({DispatcherServletAutoConfiguration.class,
     ValidationAutoConfiguration.class })
     publicclassWebMvcAutoConfiguration{

4）@EnableWebMvc将WebMvcConfigurationSupport组件导入进来

5) 导入的WebMvcConfiguraionSupport只是SpringMVC最基本的功能。 视图解析器 拦截器都得自己配

[later in this document]: https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#boot-features-spring-mvc-static-content
[later in this document 1]: https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#boot-features-spring-mvc-message-converters
[later in this document 2]: https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#boot-features-spring-message-codes
[later in this document 3]: https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#boot-features-spring-mvc-favicon
[later in this document 4]: https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#boot-features-spring-mvc-web-binding-initializer
[MVC configuration]: https://docs.spring.io/spring/docs/5.1.0.BUILD-SNAPSHOT/spring-framework-reference/web.html#mvc