springboot拦截器自动注入为null解决办法和具体原因分析

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {
	
  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(new SessionInterceptor()).excludePathPatterns("/static/**").addPathPatterns("/**");
  }
}

public class SessionInterceptor  implements HandlerInterceptor {
    @Autowired
    private IUserService  userService;

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        HttpSession session = httpServletRequest.getSession();
        String username = (String)session.getAttribute("userName");
        //获取请求信息的用户名获取对应的用户信息
        SysUser userInfo =userService.getUserInfoByUserName(username).get(0);
    }

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {
  @Bean
  public SessionInterceptor getSessionInterceptor(){
    return new SessionInterceptor();
  }

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