springboot自定义拦截器

操作说明

1、编写一个拦截器实现HandlerInterceptor接口
2、拦截器注册到容器中（实现WebMvcConfigures的addInterceptors)
3、指定拦截规则  （如果是拦截所有，静态资源也会被拦截）

LoginInterceptor.java

package com.example.springtxiangmu.interceptor;
import lombok.extern.slf4j.Slf4j;
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;

//登陆检查
@Slf4j  //能直接使用日志
public class LoginInterceptor implements HandlerInterceptor {
    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String requestURL=request.getRequestURI();
        log.info("拦截的请求路径是{}",requestURL);
//显示当前的请求路径
        HttpSession session = request.getSession();
        Object loginUser = session.getAttribute("loginUser");
//获得上面登陆的cookie
        if(loginUser!=null){
            return true;
        }
        //拦截器拦截住了，说明没有登陆，直接跳转到登陆界面
        request.setAttribute("msg","请先登陆");
        //response.sendRedirect("/");
        request.getRequestDispatcher("/").forward(request,response);
//跳转到根目录，并且转发 request、response
        return false;
    }

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

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

执行顺序（先后）

postHandle > 界面运行 >postHandle >afterCompletion

AdminWebConfig.java

@Configuration
public class AdminWebConfig implements WebMvcConfigurer {
//这里继承了WebMvcConfigurer
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
//添加上自定义的拦截器
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**/")//拦截的请求
                .excludePathPatterns("/","/login","/css/**","/fonts/**","/images/**","/js/**");// 放行的请求
    }
}

总结

流程就是，自定义拦截器实现HandlerInterceptor接口重写那三个方法，然后自定义一个配置类需要加（@Configuration)继承WebMvc接口，在里面添加自定义拦截器。
注意的是导入@Slf4j的时候，log.info  l是小写，这里写
出了Log.info 搞了好久。细心，细心，细心！
String requestURL=request.getRequestURI();
//获取当前访问页面的路径，比如访问index就会显示 index  {}相当于c中的%d占位符
        log.info("拦截的请求路径是{}",requestURL);