idea運行javaweb項目，@EnableWebMvc啟動springmvc特性

使用

@EnableWebMvc
@SpringBootApplication
public class Application  {public static void main(String[] args) {log.debug("access {}","main");SpringApplication.run(Application.class, args);}
}

WebMvcConfigurerAdapter 實現類，配置跨域，添加靜態頁面等功能

@Configuration
public class WebMvcConfig extends WebMvcConfigurerAdapter {@AutowiredRedisData redisData;@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) {registry.addResourceHandler("/**").addResourceLocations("classpath:/static/");registry.addResourceHandler("swagger-ui.html").addResourceLocations("classpath:/META-INF/resources/");registry.addResourceHandler("/webjars/**").addResourceLocations("classpath:/META-INF/resources/webjars/");}@Overridepublic void addCorsMappings(CorsRegistry registry) {registry.addMapping("/**").allowedOrigins("*").allowCredentials(true).allowedMethods("GET", "POST", "DELETE", "PUT").maxAge(3600);}}

原理

@EnableWebMvc注解注入了DelegatingWebMvcConfiguration的bean

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({DelegatingWebMvcConfiguration.class})
public @interface EnableWebMvc {
}

啟動加載所有WebMvcConfigurer實例

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();public DelegatingWebMvcConfiguration() {}@Autowired(required = false)public void setConfigurers(List<WebMvcConfigurer> configurers) {if(!CollectionUtils.isEmpty(configurers)) {this.configurers.addWebMvcConfigurers(configurers);}}
...
}

WebMvcConfigurerComposite 使用組合模式，是樹枝節點

class WebMvcConfigurerComposite implements WebMvcConfigurer {private final List<WebMvcConfigurer> delegates = new ArrayList();WebMvcConfigurerComposite() {}public void addWebMvcConfigurers(List<WebMvcConfigurer> configurers) {if(!CollectionUtils.isEmpty(configurers)) {this.delegates.addAll(configurers);}}