拦截器interceptor

Posted 2021-03-13 pinked

拦截器interceptor

1. 配置

   <mvc:interceptors>
       <mvc:interceptor>
           <!--/**回处理/后面的所有请求-->
           <mvc:mapping path="/**"/>
           <bean class="cn.pinked.config.MyInterceptor"/>
       </mvc:interceptor>
   </mvc:interceptors>

2. 拦截器

   public class MyInterceptor implements HandlerInterceptor {
   
       //return true; 执行下一个拦截器
       //return false; 不执行下一个拦截器
       public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
           System.out.println("==========preHandle==========");
           return true;
       }
   
       public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
           System.out.println("==========postHandle==========");
       }
   
       public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
           System.out.println("==========afterCompletion==========");
       }
   }

3. 输出

   ==========preHandle==========
   controller===test()执行
   ==========postHandle==========
   ==========afterCompletion==========

4. 总结

   preHandle
   调用时间：Controller方法处理之前
   若返回false，则中断执行，注意：不会进入afterCompletion

   postHandle
   调用前提：preHandle返回true
   调用时间：Controller方法处理完之后，DispatcherServlet进行视图的渲染之前，也就是说在这个方法中你可以对ModelAndView进行操作
   备注：postHandle虽然post打头，但post、get方法都能处理

   afterCompletion
   调用前提：preHandle返回true
   调用时间：DispatcherServlet进行视图的渲染之后
   多用于清理资源