自定义拦截器

首先在springmvc.xml中配置拦截器的监听

<mvc:interceptors>
    <mvc:interceptor>
        <mvc:mapping path="/**"/><!-- 拦截所有controller -->
        <!-- <mvc:exclude-mapping path=""/> --><!-- 不拦截的controller -->
        <bean id="loginInterceptor" class="com.llh.interceptor.LoginInterceptor"></bean>
    </mvc:interceptor>
</mvc:interceptors>

然后创建一个实现了HandlerInterceptor接口的类

package com.llh.interceptor;

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

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import com.llh.entity.Student;

public class LoginInterceptor implements HandlerInterceptor{

    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        // TODO Auto-generated method stub
        
    }

    @Override
    public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object arg2) throws Exception {
        // TODO Auto-generated method stub
        Student s = (Student) req.getSession().getAttribute("s");
        System.out.println("拦截器拦截");
        String context = req.getContextPath();
        System.out.println(context);
        if(s==null){
            res.sendRedirect(context+"/login.jsp");
            return false;
        }
        return true;
    }

}