[Java知识库]Springboot-14拦截器（登录检查、静态放行）

需求：

• 对于每个页面访问时都需要登录验证，如果不登录则无法访问。
• 实现拦截器需要实现HandlerInterceptor类，分为方法执行前，执行时，执行后三个处理阶段。
  
• 注册拦截器时需要实现WebMvcConfigurer类。
  

逻辑：

• 登录前检查session对象中是否存在登录用户，如果没有跳转到登录页，并往session中放入提示信息；

实现：
1、写一个拦截器，明确拦截逻辑；

package com.springbootweb.Interceptor;

import lombok.extern.slf4j.Slf4j;
import org.springframework.lang.Nullable;
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;

@Slf4j
public class WebInterceptor implements HandlerInterceptor {

    /**
     * 登录检查
     * 1、配置好拦截器要拦截哪些请求
     * 2、把这些配置放在容器中
     */

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("拦截的请求路径为："+request.getRequestURI());
        HttpSession session = request.getSession();
        Object object = session.getAttribute("userInfo");
        if(object == null){
            //此处未登录，跳转登录页
            session.setAttribute("msg","请先登录");
//            response.sendRedirect("/login");
            request.getRequestDispatcher("/login").forward(request,response);
            return false;
        }
        return  true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
        log.info("");
    }

}

2、将拦截器注册到bean中；

package com.springbootweb.Config;

import com.springbootweb.Interceptor.WebInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new WebInterceptor())
                .addPathPatterns("/**") //拦截所有请求
                .excludePathPatterns("/login","/","/css/**","/files/**","/images/**","/static/**"); //放行请求
    }
}

• 创建config路径进行注册，注册时说明需要拦截那些路径，那些路径不拦截。
• 拦截器会拦截静态资源，要注意放行。
  

3、Controller

package com.springbootweb.Controller;

import com.springbootweb.Entiy.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.thymeleaf.util.StringUtils;

import javax.servlet.http.HttpSession;

@Controller
public class UserController {

    @GetMapping(value = {"/","/login"})
    public String toLogin(){
        return "login";
    }

//    @PostMapping("/index")
//    public String toIndex(String username,String password){
//        return "index";
//    }

    //每次刷新页面都是重新登录，需要进行请求转发处理
    @PostMapping("/index")
    public String toIndex(User user, HttpSession session, Model model){
        if(!StringUtils.isEmpty(user.getUserName()) && user.getPassword().equals("123456")){
            session.setAttribute("userInfo",user);
            return "redirect:/indexPage";
        } else {
            model.addAttribute("msg","账号或密码错误");
            return "login";
        }
    }

    @GetMapping("/indexPage")
    public  String indexPage(HttpSession session,Model model){
//        Object user = session.getAttribute("userInfo");
//        if(user != null){
            return "index";
//        } else {
//            model.addAttribute("msg","请先登录");
//            return "login";
//        }
    }
}

流程：

ptr——>方法——>post——>页面渲染——>after