解决Spring Boot 拦截器注入service为空的问题

一、原因分析

拦截器加载的时间点在springcontext之前，所以在拦截器中注入自然为null

二、解决方法

1.需要在拦截器上加入注解@Component

@Component
public class MyInterceptor implements HandlerInterceptor {
    //想要注入的类
    @Autowired
    UserService userService;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        System.out.println("request before 拦截");
        return true;

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("post 拦截");

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("after 拦截");
    }
}

2.拦截器配置

@Configuration
public class MyWebAppConfigurer extends WebMvcConfigurerAdapter {

   //关键，将拦截器作为bean写入配置中
   @Bean
   public MyInterceptor myInterceptor(){
       return new MyInterceptor();
   }

   @Override
   public void addInterceptors(InterceptorRegistry registry) {
       //多个拦截器组成一个拦截器链
       // addPathPatterns用于添加拦截规则
       // excludePathPatterns用户排除拦截
       registry.addInterceptor(myInterceptor()).addPathPatterns("/**"); //对来自/** 全路径请求进行拦截
       super.addInterceptors(registry);
   }
}