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。
