1、定义interceptor

package com.example.interceptor;
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 {
        System.out.println("自定义拦截器开始执行");
        User user = request.getSession().getAttribute("user");
        if(user==null){
            request.getRequestDispatcher("/index").forward(request, response);
            return false;
        }
        return true;
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {

    }
}

2、注册拦截器

package com.example.config;

import com.example.interceptor.LoginInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
public class MyMvcConfig extends WebMvcConfigurerAdapter {
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/index").setViewName("index");
        registry.addViewController("/indexTest").setViewName("index");
    }

    //注册拦截器
    **@Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/**").excludePathPatterns("/index");
    }
}**

注意：其中LoginInterceptor()).addPathPatterns("/**").excludePathPatterns("/index");中的addPathterns中的参数是所要拦截的路径，excludePathPatterns中的参数是：不拦截的路径