SpringMVC拦截器配置及运行流程解析

package com.imooc.core;

import com.imooc.bean.User;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginInterceptor implements HandlerInterceptor {


  //在业务处理器被调用前的方法，若是返回false则不会继续进入业务处理器
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    User user = (User)request.getSession().getAttribute("session_user");
    if(user==null) {
      response.sendRedirect(request.getContextPath()+"/login");
      return false;//会终止所有的请求
    }
    return true;
  }

  //在业务处理器被调用后，dispatcher响应客户端前的方法，一般用于生成日志文件时调用
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

  }

  //dispatcher响应客户端后的方法，一般用于资源的清理
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

  }
}

<!-- 拦截器的注册 -->
  <mvc:interceptors>
    <mvc:interceptor>
       <!--**表示往后的所有子目录也包括进来-->
      <mvc:mapping path="/user/**"></mvc:mapping>
      <!--exclude-mapping在所有拦截中进行排除，一般在通配符会有意义。-->
      <!--即以下的方法不会被拦截-->
      <mvc:exclude-mapping path="/user/updatepwd"></mvc:exclude-mapping>
      <mvc:exclude-mapping path="/user/updatebackground/*"></mvc:exclude-mapping>
      <!--填写之前配置好的拦截器-->
      <bean class="com.imooc.core.LoginInterceptor"></bean>
    </mvc:interceptor>
  </mvc:interceptors>

<!-- 拦截器的注册 -->
  <mvc:interceptors>

    <!--先注册先执行-->
    <mvc:interceptor>
      <mvc:mapping path="/user/**"/>
      <bean class="com.imooc.core.LogInterceptor"></bean>
    </mvc:interceptor>

    <mvc:interceptor>
      <mvc:mapping path="/user/**"></mvc:mapping>
      <!--exclude-mapping在所有拦截中进行排除，一般在通配符会有意义。-->
      <mvc:exclude-mapping path="/user/updatepwd"></mvc:exclude-mapping>
      <mvc:exclude-mapping path="/user/updatebackground/*"></mvc:exclude-mapping>
      <bean class="com.imooc.core.LoginInterceptor"></bean>
    </mvc:interceptor>
  </mvc:interceptors>