SpringBoot——SpringMvc自动配置与扩展

刺骨的言语ヽ痛彻心扉 2022-05-21 01:39 215阅读 0赞

一、以前xml配置

<mvc:annotation-driven  message-codes-resolver ="bean ref" validator="" conversion-service="">
    </mvc:annotation-driven>

现在改为：

@Configuration
    public class MyWebMvcConfigurer implements WebMvcConfigurer {
        /**
         * 自动转换时间格式
         *
         * @param registry date
         */
        @Override
        public void addFormatters(FormatterRegistry registry) {
            registry.addFormatter(new DateFormatter("yyyy-MM-dd HH:mm:ss"));
        }
    }

注意：不需要再次在配置中指定 `<mvc:annotation-driven />`或者是配置类中添加 `@EnableWebMVC`，因为这样配置会让spring boot不再装配Spring MVC相关的配置，又回到了自己配置SpringMVC的传统老路，体现不了采用SpringBoot的好处。

我们可以继承`WebMvcConfigurerAdapter`来添加我们的自定义配置。

WebMvcConfigurerAdapter源码:

public abstract class WebMvcConfigurerAdapter implements WebMvcConfigurer {
        public WebMvcConfigurerAdapter() {
        }
    
        public void configurePathMatch(PathMatchConfigurer configurer) {
        }
    
        public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
        }
    
        public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
        }
    
        public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        }
    
        public void addFormatters(FormatterRegistry registry) {
        }
    
        public void addInterceptors(InterceptorRegistry registry) {
        }
    
        public void addResourceHandlers(ResourceHandlerRegistry registry) {
        }
    
        public void addCorsMappings(CorsRegistry registry) {
        }
    
        public void addViewControllers(ViewControllerRegistry registry) {
        }
    
        public void configureViewResolvers(ViewResolverRegistry registry) {
        }
    
        public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        }
    
        public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) {
        }
    
        public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        }
    
        public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        }
    
        public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
        }
    
        public void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
        }
    
        public Validator getValidator() {
            return null;
        }
    
        public MessageCodesResolver getMessageCodesResolver() {
            return null;
        }
    }

#### 不推荐使用WebMvcConfigurationSupport类. ####

也可以配置类继承于WebMvcConfigurationSupport类即可

源码分析：

@Configuration
    @ConditionalOnWebApplication
    @ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurerAdapter.class})
    @ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
    @AutoConfigureOrder(-2147483638)
    @AutoConfigureAfter({DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class})
    public class WebMvcAutoConfiguration {
        public static final String DEFAULT_PREFIX = "";
        public static final String DEFAULT_SUFFIX = "";
    
        public WebMvcAutoConfiguration() {
        }

这是因为在 springboot的web自动配置类 WebMvcAutoConfiguration 上有条件注解

@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)

这个注解的意思是在项目类路径中 **缺少** WebMvcConfigurationSupport类型的bean时改自动配置类才会生效，所以继承 WebMvcConfigurationSupport 后需要自己再重写相应的方法。