spring boot springMVC扩展配置实现解析

@Configuration
public class MyMvcConfig Implements WebMvcConfigurer {

 @Override
 public void addViewControllers(ViewControllerRegistry registry) {
  // super.addViewControllers(registry);
  //浏览器发送 /success请求来到 success
  registry.addViewController("/success").setViewName("success");
 }
}

@Configuration
@ConditionalOnWebApplication(
 type = Type.SERVLET
)
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class})
@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
@AutoConfigureOrder(-2147483638)
@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class})
public class WebMvcAutoConfiguration {
 ....//省略部分代码
 @Configuration
 @Import({WebMvcAutoConfiguration.EnableWebMvcConfiguration.class}) // 导入了EnableWebMvcConfiguration这个类 addResourceHandlers方法
 @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class})
 @Order(0)
 public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer, ResourceLoaderAware {
  　　
　　　　...//省略部分代码
  public void addResourceHandlers(ResourceHandlerRegistry registry) {//实现WebMvcConfigurer 这个类的
   if(!this.resourceProperties.isAddMappings()) {
    logger.debug("Default resource handling disabled");
   } else {
    Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
    CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
    if(!registry.hasMappingForPattern("/webjars/**")) {
     this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"}).addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"}).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
    }

    String staticPathPattern = this.mvcProperties.getStaticPathPattern();
    if(!registry.hasMappingForPattern(staticPathPattern)) {
     this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{staticPathPattern}).addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations())).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
    }

   }
  }
}

@Configuration
 public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {
  private final WebMvcProperties mvcProperties;
  private final ListableBeanFactory beanFactory;
  private final WebMvcRegistrations mvcRegistrations;
 　　　　...// 省略
}

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
 private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
  ...//省略
 /**
  * 从容器中拿到所有 WebMvcConfigurer 的实现类。遍历添加到 configurers 
  * [required description]
  * @type {[type]}
  */
 @Autowired( required = false ) // 自动装配
 public void setConfigurers(List<WebMvcConfigurer> configurers) {
  if(!CollectionUtils.isEmpty(configurers)) {
   this.configurers.addWebMvcConfigurers(configurers);
  }
 }
 ...//省略
 /**
  * 当调用addResourceHandlers 时 ,调用的 成员configurers的 addResourceHandlers
  * [addResourceHandlers description]
  * @param {[type]} ResourceHandlerRegistry registry [description]
  */
 protected void addResourceHandlers(ResourceHandlerRegistry registry) {
  this.configurers.addResourceHandlers(registry);
 }
 ...//省略
}

class WebMvcConfigurerComposite implements WebMvcConfigurer {
 private final List<WebMvcConfigurer> delegates = new ArrayList<WebMvcConfigurer>();
 @Override
 public void addViewControllers(ViewControllerRegistry registry) { // 遍历 把 所有WebMvcConfigurer的 addViewControllers方法调用一遍
  for (WebMvcConfigurer delegate : this.delegates) {
   delegate.addViewControllers(registry);
  }
 }
}