精通SpringBoot——第三篇：详解WebMvcConfigurer接口

SpringBoot 确实为我们做了很多事情， 但有时候我们想要自己定义一些Handler，Interceptor，ViewResolver，MessageConverter，该怎么做呢。在Spring Boot 1.5版本都是靠重写WebMvcConfigurerAdapter的方法来添加自定义拦截器，消息转换器等。SpringBoot 2.0 后，该类被标记为@Deprecated。因此我们只能靠实现WebMvcConfigurer接口来实现。接下来让我们来看看这个接口类吧！（列举下常用的方法供参考）

package com.developlee.config; import com.alibaba.fastjson.serializer.SerializerFeature; import com.alibaba.fastjson.support.config.FastJsonConfig; import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter; import com.developlee.configurer.USLocalDateFormatter; import org.springframework.format.FormatterRegistry; import org.springframework.http.MediaType; import org.springframework.http.converter.HttpMessageConverter; import org.springframework.http.converter.json.JsonbHttpMessageConverter; import org.springframework.web.bind.annotation.RequestMethod; import org.springframework.web.servlet.config.annotation.CorsRegistry; import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter; import java.time.LocalDate; import java.util.ArrayList; import java.util.List; import java.util.Locale; /** * @TODO // * @Author Lensen * @Date 2018/7/21 * @Description 实现WebMvcConfigurer接口， */ @Configuration public class WebConfig implements WebMvcConfigurer { /** * 添加类型转换器和格式化器 * @param registry */ @Override public void addFormatters(FormatterRegistry registry) { registry.addFormatterForFieldType(LocalDate.class, new USLocalDateFormatter()); } /** * 跨域支持 * @param registry */ @Override public void addCorsMappings(CorsRegistry registry) { registry.addMapping("/**") .allowedOrigins("*") .allowCredentials(true) .allowedMethods("GET", "POST", "DELETE", "PUT") .maxAge(3600 * 24); } /** * 添加静态资源--过滤swagger-api (开源的在线API文档) * @param registry */ @Override public void addResourceHandlers(ResourceHandlerRegistry registry) { //过滤swagger registry.addResourceHandler("swagger-ui.html") .addResourceLocations("classpath:/META-INF/resources/"); registry.addResourceHandler("/webjars/**") .addResourceLocations("classpath:/META-INF/resources/webjars/"); registry.addResourceHandler("/swagger-resources/**") .addResourceLocations("classpath:/META-INF/resources/swagger-resources/"); registry.addResourceHandler("/swagger/**") .addResourceLocations("classpath:/META-INF/resources/swagger*"); registry.addResourceHandler("/v2/api-docs/**") .addResourceLocations("classpath:/META-INF/resources/v2/api-docs/"); } } /** * 配置消息转换器--这里我用的是alibaba 开源的 fastjson * @param converters */ @Override public void configureMessageConverters(List<HttpMessageConverter<?>> converters) { //1.需要定义一个convert转换消息的对象; FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter(); //2.添加fastJson的配置信息，比如：是否要格式化返回的json数据; FastJsonConfig fastJsonConfig = new FastJsonConfig(); fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue, SerializerFeature.WriteNullStringAsEmpty, SerializerFeature.DisableCircularReferenceDetect, SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteDateUseDateFormat); //3处理中文乱码问题 List<MediaType> fastMediaTypes = new ArrayList<>(); fastMediaTypes.add(MediaType.APPLICATION_JSON_UTF8); //4.在convert中添加配置信息. fastJsonHttpMessageConverter.setSupportedMediaTypes(fastMediaTypes); fastJsonHttpMessageConverter.setFastJsonConfig(fastJsonConfig); //5.将convert添加到converters当中. converters.add(fastJsonHttpMessageConverter); } @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(new ReqInterceptor()).addPathPatterns("/**"); } } 

添加一个Interceptor，作为测试

package com.developlee.configurer; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.handler.HandlerInterceptorAdapter; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @TODO // * @Author Lensen * @Date 2018/7/21 * @Description 请求Interceptor */ public class ReqInterceptor extends HandlerInterceptorAdapter { @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { System.out.println("Interceptor preHandler method is running !"); return super.preHandle(request, response, handler); } @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { System.out.println("Interceptor postHandler method is running !"); super.postHandle(request, response, handler, modelAndView); } @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { System.out.println("Interceptor afterCompletion method is running !"); super.afterCompletion(request, response, handler, ex); } @Override public void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { System.out.println("Interceptor afterConcurrentHandlingStarted method is running !"); super.afterConcurrentHandlingStarted(request, response, handler); } } 

写个controller测试下

@Controller @RequestMapping("/locale") public class LocaleController { @GetMapping("/date") @ResponseBody public String locale(Locale locale){ System.out.println("Controller is running !"); return "Hello" + USLocalDateFormatter.getPattern(locale); } }

请求地址： http://localhost:8080/locale/date ,看看控制台打印信息

//SpringMvc请求处理的执行过程 Interceptor preHandler method is running ! Controller is running ! Interceptor postHandler method is running ! Interceptor afterCompletion method is running ! 

题外话：从WebMvcConfigurer这个接口中，可以看到JDK8的一些新特性——在接口中新增了default方法和static方法，这两种方法可以有方法体。大家可以业余时间去了解下。这两种新特性为我们编写代码带来了更多改变，让代码变得更加简洁。