springboot 实现登录拦截器

1、实现HandlerInterceptor 接口

package com.liu.bootadmin.intercepteor;

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 LoginInterceptor implements HandlerInterceptor {

    /**
     * 目标方法执行之前
     * @param request
     * @param response
     * @param handler
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        HttpSession session =request.getSession();
        //检查登录信息
        Object loginUser = session.getAttribute("loginUser");
        System.out.println("loginUser==>"+loginUser);
        if (loginUser != null) {
            //放行
            return true;
        }
        //拦截，未登录，跳转到登录页面
        request.setAttribute("msg","请登录后重新访问");
        request.getRequestDispatcher("/").forward(request ,response);
        return false;

    }


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

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,
                                Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }
}

##2、配置拦截器
```java
package com.liu.bootadmin.config;

import com.liu.bootadmin.intercepteor.LoginInterceptor;
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 AdminWebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**")//所有请求都被拦截包括静态资源
                .excludePathPatterns("/", "/login", "/css/**", "/fonts/**", "/images/**", "/js/**"); //放行的请求
    }


}