springmvc实用篇 -- WebMvcConfigurer

WebMvcConfigurer这个接口干什么用，文字上的描述我就不再说了，我们直接从功能入手就知道这玩意能帮我们做些什么事

首先我们打开这个接口所定义的哪些方法

public interface WebMvcConfigurer {
	default void configurePathMatch(PathMatchConfigurer configurer) {}
	default void configureContentNegotiation(ContentNegotiationConfigurer configurer) {}
	default void configureAsyncSupport(AsyncSupportConfigurer configurer) {}
	default void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {}
	default void addFormatters(FormatterRegistry registry) {}
	default void addInterceptors(InterceptorRegistry registry) {}
	default void addResourceHandlers(ResourceHandlerRegistry registry) {}
	default void addCorsMappings(CorsRegistry registry) {}
	default void addViewControllers(ViewControllerRegistry registry) {}
	default void configureViewResolvers(ViewResolverRegistry registry) {}
	default void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {}
	default void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> handlers) {}
	default void configureMessageConverters(List<HttpMessageConverter<?>> converters) {}
	default void extendMessageConverters(List<HttpMessageConverter<?>> converters) {}
	default void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {}
	default void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {}
	@Nullable
	default Validator getValidator() {
		return null;
	}
	@Nullable
	default MessageCodesResolver getMessageCodesResolver() {
		return null;
	}
}

这里面吧定义了N多个方法供我们自定义添加配置，其中这里我就挑几个比较常用的来示范下它的用途

 

一、addInterceptors

从名字上看我们就可以猜到是添加自定义拦截器的，下面来示范下

1.定义HandlerInterceptor

 public class MyInterceptor implements HandlerInterceptor{
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            System.out.println("preHandle:假设这里请求前进行判断是否有登陆");
            //假设这里请求前进行判断是否有登陆,有则return true，无则false
            return true;
        }

        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
            //请求中处理，也就是HandlerAdapter处理Handler后在返回视图前执行该方法
            System.out.println("postHandle==requestUrl:"+request.getRequestURI());
        }

        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
            //提交视图后执行该方法
            System.out.println("afterCompletion==requestUrl:"+request.getRequestURI());
        }
    }

2.定义WebMvcConfigurer添加addInterceptors

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**").excludePathPatterns("/user/login");
    }
}

.addPathPatterns("/**")表示拦截所有请求；.excludePathPatterns("/user/login")表示不拦截该请求

3.定义controller

@RestController
@RequestMapping("/user")
public class UserController {
    @RequestMapping("/login")
    public String index() {
        return "hello springmvc!login";
    }
    @RequestMapping("/get")
    public String get(){
        return "hello springmvc!get";
    }
}

4.执行结果

1）调用login方法：

因为是login故这里是不会进拦截，所以就不会打印任何东西

2）请求get方法：

这里进了拦截器所以会进行打印操作

 

二、addArgumentResolvers

从方法参数上可以猜测到添加自定义HandlerMethodArgumentResolver参数解析，下面我们来操作看下

1.定义HandlerMethodArgumentResolver：

class MyHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {
        @Override
        public boolean supportsParameter(MethodParameter parameter) {
            return parameter.getParameterType().getName().equals(UserA.class.getName());//仅对UserA有效
        }

        @Override
        public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
            //模拟从session中获取登陆的用户信息
            Object attribute = webRequest.getAttribute("user", NativeWebRequest.SCOPE_SESSION);//Request中的用户属性
            //然后放入UserA的对象里
            //这里直接写死一个
            attribute = new UserA("sessionUserName", 20);
            return attribute;
        }
    }

2.定义WebMvcConfigurer添加addArgumentResolvers：

@Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        resolvers.add(new MyHandlerMethodArgumentResolver());
    }

3.定义controller：

@RequestMapping("/index")
    public String index(UserA userA){
        return "hello springmvc!userA:"+userA;
    }

4.执行结果：

这里能看取到在resolveArgument赋值的userA

 

三、addResourceHandlers

静态资源访问

1.我们直接重写addResourceHandlers方法：

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/file/**").addResourceLocations("classpath:/static/","file:D:/tomcat/");
    }
}

addResourceHandler("/file/**")添加对外访问路径，addResourceLocations添加本地目录资源路径

2.本地资源：

3.访问资源:

 

ok.其他的方法我就不再尝试了，网上资料一大堆，主要这里是记录下有这么个配置类叫做WebMvcConfigurer，他非常好用