package blog.interceptor;
import blog.entity.User;
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 UserLoginInterceptor implements HandlerInterceptor {
    /***
     * 在請(qǐng)求處理之前進(jìn)行調(diào)用(Controller方法調(diào)用之前)
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("執(zhí)行了攔截器的preHandle方法");
        try {
            HttpSession session = request.getSession();
            //統(tǒng)一攔截（查詢當(dāng)前session是否存在user）(這里user會(huì)在每次登錄成功后，寫入session)
            User user = (User) session.getAttribute("user");
            if (user != null) {
                return true;
            }
            response.sendRedirect(request.getContextPath() + "login");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
        //如果設(shè)置為false時(shí)，被請(qǐng)求時(shí)，攔截器執(zhí)行到此處將不會(huì)繼續(xù)操作
        //如果設(shè)置為true時(shí)，請(qǐng)求將會(huì)繼續(xù)執(zhí)行后面的操作
    }
    /***
     * 請(qǐng)求處理之后進(jìn)行調(diào)用，但是在視圖被渲染之前（Controller方法調(diào)用之后）
     */
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("執(zhí)行了攔截器的postHandle方法");
    }
    /***
     * 整個(gè)請(qǐng)求結(jié)束之后被調(diào)用，也就是在DispatchServlet渲染了對(duì)應(yīng)的視圖之后執(zhí)行（主要用于進(jìn)行資源清理工作）
     */
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("執(zhí)行了攔截器的afterCompletion方法");
    }
}

package blog.config;
import blog.interceptor.UserLoginInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Configuration
public class LoginConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //注冊(cè)TestInterceptor攔截器
        InterceptorRegistration registration = registry.addInterceptor(new UserLoginInterceptor());
        registration.addPathPatterns("/**"); //所有路徑都被攔截
        registration.excludePathPatterns(    //添加不攔截路徑
                "/login",                    //登錄路徑
                "/**/*.html",                //html靜態(tài)資源
                "/**/*.js",                  //js靜態(tài)資源
                "/**/*.css"                  //css靜態(tài)資源
        );
    }
}

@RequestMapping(value = {"", "/", "/index"}, method = RequestMethod.GET)
public String index(Model model, HttpServletRequest request) {
    User user = (User) request.getSession().getAttribute("user");
    model.addAttribute("user", user);
    return "users/index";
}
@RequestMapping(value = {"/login"}, method = RequestMethod.GET)
public String loginIndex() {
    return "users/login";
}
@RequestMapping(value = {"/login"}, method = RequestMethod.POST)
public String login(@RequestParam(name = "username")String username, @RequestParam(name = "password")String password,
                    Model model, HttpServletRequest request) {
    User user = userService.getPwdByUsername(username);
    String pwd = user.getPassword();
    String password1 = MD5Utils.md5Code(password).toUpperCase();
    String password2 = MD5Utils.md5Code(password1).toUpperCase();
    if (pwd.equals(password2)) {
        model.addAttribute("user", user);
        request.getSession().setAttribute("user", user);
        return "redirect:/index";
    } else {
        return "users/failed";
    }
}