加上@Service注解即可解决

调用的时候加上@Autowired注解

代码如下:

package com.nice.interceptor;

import com.nice.mapper.UserMapper;
import com.nice.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * The current class is   ...
 * This ide name is IntelliJ IDEA.
 * The current project name is nice-community.
 * The current package name is com.nice.interceptor.
 *
 * @author nice
 * @version jdk1.8
 * @date 2019/11/17 8:52
 */
@Service
public class SessionInterceptor implements HandlerInterceptor {

    @Autowired
    private UserMapper userMapper;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        Cookie[] cookies = request.getCookies();
        if (cookies !=null && cookies.length != 0) {
            for (Cookie cookie : cookies) {
                if (cookie.getName().equals("token")) {
                    String token = cookie.getValue();
                    User user = userMapper.findByToken(token);
                    if (user != null) {
                        request.getSession().setAttribute("user", user);
                    }
                    break;
                }
            }
        }
        return true;
    }

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

    }

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

    }
}

package com.nice.interceptor;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.i18n.LocaleChangeInterceptor;
import org.springframework.web.servlet.theme.ThemeChangeInterceptor;

/**
 * The current class is   ...
 * This ide name is IntelliJ IDEA.
 * The current project name is nice-community.
 * The current package name is com.nice.interceptor.
 *
 * @author nice
 * @version jdk1.8
 * @date 2019/11/17 8:42
 */
@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {

    @Autowired
    private SessionInterceptor sessionInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(sessionInterceptor).addPathPatterns("/**");
    }

}