登录权限检查（SpringMVC）

package com.day04test.interceptor;

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

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

//拦截器
public class LoginInterceptor implements HandlerInterceptor{

    //请求处理完毕，输出之前
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        System.out.println("afterCompletion");
        
    }

    //Controller之后
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        System.out.println("postHandle");
        
    }
    //Controller之前调用
    /*
     * 如果返回为false，则拦截
     * (non-Javadoc)
     * @see org.springframework.web.servlet.HandlerInterceptor#preHandle(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, java.lang.Object)
     */
    public boolean preHandle(HttpServletRequest request,
            HttpServletResponse response,
            Object arg2) throws Exception {
        
        System.out.println("preHandle");
        //追加登录检查
        HttpSession session=request.getSession();
        String name=(String)session.getAttribute("username");
        if(name!=null){//登录过
            return true;//继续执行MVC后续流程
        }else{
            //未登录过或登录失效
            response.sendRedirect("tologin.do");
            return true;//终止MVC后续流程
        }
        
    }

}

<!-- 配置拦截器 -->
<mvc:interceptors>
    <mvc:interceptor>
        <!-- 指明路径:拦截那些请求 -->
        <mvc:mapping path="/**"/>
        <!-- 放过那些请求 -->
        <mvc:exclude-mapping path="/tologin.do"/>
        <mvc:exclude-mapping path="/login3.do"/>
        <bean class="com.day04test.interceptor.LoginInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>