springboot——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;

/**

• @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> 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 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;

/**

• @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。