打卡6:Spring MVC基礎之基本配置

一. 靜態資源映射

1. 簡述
   通過在配置裏重寫addResourceHandlers方法來實現靜態文件（js、css、圖片）的直接訪問。

2. 示例

   package com.muzi.springboot01.mvc3;
   
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.ComponentScan;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.web.servlet.config.annotation.EnableWebMvc;
   import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
   import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
   import org.springframework.web.servlet.view.InternalResourceViewResolver;
   import org.springframework.web.servlet.view.JstlView;
   
   @EnableWebMvc //開啓Spring MVC支持
   @Configuration
   @ComponentScan("com.muzi.springboot01.mvc3")
   public class MyMvcConfig extends WebMvcConfigurerAdapter {
   
       @Bean
       public InternalResourceViewResolver viewResolver() {
           InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
           viewResolver.setPrefix("/WEB-INF/classes/views/");
           viewResolver.setSuffix(".jsp");
           viewResolver.setViewClass(JstlView.class);
           return viewResolver;
       }
   
       @Override
       public void addResourceHandlers(ResourceHandlerRegistry registry) {
           /**
            * addResourceHandler：文件放置的目錄
            * addResourceLocations：對外暴露的訪問路徑
            */
           registry.addResourceHandler("/assets/**").addResourceLocations("classpath:/assets");
       }
   }
   

二. 攔截器配置

1. 簡述
   攔截器即對每一個請求處理請後進行相關業務處理。

2. 示例
   攔截器示例：計算每一次請求的處理時間

   import org.springframework.web.servlet.ModelAndView;
   import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
   
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   
   public class DemoInterceptor extends HandlerInterceptorAdapter {
       @Override
       public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
           long startTime = System.currentTimeMillis();
           request.setAttribute("startTime", startTime);
           return true;
       }
   
       @Override
       public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
           long startTime = (long) request.getAttribute("startTime");
           request.removeAttribute("startTime");
           long endTime = System.currentTimeMillis();
           System.out.println("請求處理時間爲："+new Long(endTime - startTime) + "ms");
           request.setAttribute("handlingTime", endTime - startTime);
       }
   }
   

   配置

   @Configuration
   @EnableWebMvc //開啓Spring MVC支持
   @ComponentScan("com.muzi.mvc3")
   public class MyMvcConfig extends WebMvcConfigurerAdapter {
   
       @Bean
       public InternalResourceViewResolver viewResolver() {
           InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
           viewResolver.setPrefix("/WEB-INF/classes/views/");
           viewResolver.setSuffix(".jsp");
           viewResolver.setViewClass(JstlView.class);
           return viewResolver;
       }
   
       @Override
       public void addResourceHandlers(ResourceHandlerRegistry registry) {
           /**
            * addResourceHandler：文件放置的目錄
            * addResourceLocations：對外暴露的訪問路徑
            */
           registry.addResourceHandler("/assets/**").addResourceLocations("classpath:/assets");
       }
   
       @Bean
       public DemoInterceptor demoInterceptor() {
           return new DemoInterceptor();
       }
   
       @Override
       public void addInterceptors(InterceptorRegistry registry) {
           registry.addInterceptor(demoInterceptor());
       }
   }