springMVC 用户登录权限验证实现过程解析

package com.huitong.util;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class StudentAuth implements HandlerInterceptor {
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    HttpSession session = request.getSession();
    Object stu = session.getAttribute("student");
    if( stu == null ){
      response.sendRedirect("/webapp1/index.jsp");
      return false;
    }
    return true;
  }
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
  }
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
  }
}

<mvc:interceptors>
    <mvc:interceptor>
      <!-- 先匹配所有路径，然后排除不需要检查的路径 -->
      <mvc:mapping path="/**"/>

      <!-- 与登录相关的请求 -->
      <mvc:exclude-mapping path="/*.jsp"/>
      <mvc:exclude-mapping path="/student/login.action"/>
      <mvc:exclude-mapping path="/student/register.action"/>

      <!-- 以下是静态资源 -->
      <mvc:exclude-mapping path="/images/**" />
      <mvc:exclude-mapping path="/css/**" />
      <mvc:exclude-mapping path="/font/**" />
      <mvc:exclude-mapping path="/js/**" />
      <mvc:exclude-mapping path="/datepicker/**" />

      <!-- 用户是否已经登录的检查bean -->
      <bean class="com.huitong.util.StudentAuth"/>
        
    </mvc:interceptor>
  </mvc:interceptors>