SpringMVC拦截器超详细解读

package com.qcby.controller;
import com.qcby.model.User1;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import javax.servlet.http.HttpSession;
@Controller
@RequestMapping("/to")
public class LoginController {
    /**
     * 跳转到登录页
     * @return
     */
    @RequestMapping("/toLogin")
    public String loginPage(){
        System.out.println("跳转到登录页");
        return "login";
    }
    /**
     * 用户登录，成功到主页，失败回到登录页
     * @param user
     * @param model
     * @param session
     * @return
     */
    @RequestMapping(value = "/login",method = RequestMethod.POST)
    public String login(User1 user, Model model, HttpSession session){
        if(user.getUsername() !=null && user.getUsername().equals("admin")
                && user.getPassword() !=null && user.getPassword().equals("123456")){
            System.out.println("用户登录功能实现");
            //将用户添加到session保存
            session.setAttribute("user",user);
            return "suc";
        }
        model.addAttribute("msg","账户或密码错误，请重新登录");
        return "login";
    }
}

package com.qcby.config;
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 {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //获取请求的url
        String url=request.getRequestURI();
        if(!url.contains("login")){
            //不是登录请求，判断有没有登录
            if(request.getSession().getAttribute("user")!=null){
                return true; //说明已经登录，则放行
            }else{
                request.setAttribute("msg","你还没有登录，请登录。。。");
                request.getRequestDispatcher("/html/login.html").forward(request,response);
            }
        }else {
            //登录请求，放行
            return true;
        }
        return true;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }
}

<!--配置拦截器-->
<mvc:interceptors>
    <mvc:interceptor>
        <mvc:mapping path="/**"/> <!--/**表示所有url-->
        <bean class="com.qcby.Interceptor.LoginInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>