SpringMVC_拦截器

4.拦截器

4.1拦截器概述

• 概述：一种动态拦截方法调用的机制，在SpringMVC中动态拦截控制器方法的执行
• 实际开发中，静态资源（HTML/CSS）不需要交给框架处理，需要拦截的是动态资源

4.2图示

• 图示

  

  4.3案例实现

• 模拟没有登录拦截操作

• 新定义拦截器

  @Component
  public class LoginInterceptor implements HandlerInterceptor {
      @Override
      public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
          System.out.println("登录拦截操作");
          String username = request.getParameter("username");
          if("sy".equals(username)){
              return true;
          }
          System.out.println("preHandle");
          return false;
      }
  
      @Override
      public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
          System.out.println("postHandle");
      }
  
      @Override
      public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
          System.out.println("afterCompletion");
      }
  }
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• 修改SpringMvc 配置

  @Configuration
  @ComponentScan({"cn.sycoder.controller","cn.sycoder.interceptor"})
  @EnableWebMvc
  public class SpringMvcConfig implements WebMvcConfigurer {
  
      @Autowired
      LoginInterceptor loginInterceptor;
  
      @Override
      public void addInterceptors(InterceptorRegistry registry) {
          registry.addInterceptor(loginInterceptor).addPathPatterns("/item","/item/*");
      }
  }
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• controller 确实被拦截

  @RestController
  @RequestMapping("/item")
  public class ItemController {
  
      @GetMapping("/{id}")
      public String getById(@PathVariable Long id){
          return "query"+id;
      }
  
      @GetMapping
      public String list(){
          return "list";
      }
  }
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4.4拦截器参数讲解

• HttpServletRequest request
• HttpServletResponse response
• Object handler 相当于是对访问接口的一种包装

4.5拦截器链

• 新增拦截器

  @Component
  public class AuthInterceptor implements HandlerInterceptor {
      @Override
      public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
          System.out.println("权限拦截的方法");
          return true;
      }
  
      @Override
      public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
          System.out.println("权限拦截的postHandle方法");
      }
  
      @Override
      public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
          System.out.println("权限拦截的afterCompletion方法");
      }
  }
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• 添加到拦截器链中

  @Configuration
  @ComponentScan({"cn.sycoder.controller","cn.sycoder.interceptor"})
  @EnableWebMvc
  public class SpringMvcConfig implements WebMvcConfigurer {
  
      @Autowired
      LoginInterceptor loginInterceptor;
  
      @Autowired
      AuthInterceptor authInterceptor;
  
      @Override
      public void addInterceptors(InterceptorRegistry registry) {
          registry.addInterceptor(loginInterceptor).addPathPatterns("/item","/item/*");
          registry.addInterceptor(authInterceptor).addPathPatterns("/item","/item/*");
      }
  }
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• 拦截器链注意点

  • 拦截器有着先进后出的原则
  • preHandle : 与配置顺序保持一致的执行顺序
  • postHandle：与配置顺序相反，可能不运行
  • afterCompletion：与配置顺序相反，可能不运行

4.6面试题拦截器与过滤器的区别

• 区别

  • 技术所属不同
    • 过滤器：Servlet 技术
    • 拦截器：SpringMVC技术
  • 拦截内容不同
    • Filter : 是对所有访问进行过滤
    • Interceptor：仅仅针对访问SpringMVC

• 访问流程