SpringBoot使用拦截器Interceptor拦截指定url，进行对应操作

现在有个需求，我只想要带有 /api/{path}的才能访问，并且path传的参必须在数据库中里面存在

    @GetMapping("/api/{path}")
    public String getData(@PathVariable String path){
        String data = urlService.getData(path);
        return data;
    }

必须要传/api/get才能访问，传其他的不行

代码实现
拦截器

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.donglin.entity.UrlEntity;
import com.donglin.mapper.UrlMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.servlet.HandlerInterceptor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.List;

public class URLInterceptor implements HandlerInterceptor {

    @Autowired
    private UrlMapper urlMapper;

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String path = request.getServletPath();
        String[] split = path.split("/");
        path = split[split.length-1];
        QueryWrapper<UrlEntity> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("path", path);
        List<UrlEntity> list = urlMapper.selectList(queryWrapper);
        if (list.size() != 0) {
            // 进行前置处理
            return true;
            // 或者 return false; 禁用某些请求
        } else {
            return false;
        }
    }
}

配置类

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {


    @Bean
    public URLInterceptor urlInterceptor(){
        return new URLInterceptor();
    }

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

提醒一下小坑(上面代码是对的)
urlMapper为空

    @Autowired
    private UrlMapper urlMapper;

为null的原因
原因是因为拦截器的加载在springcontext之前，所以自动注入的mapper是null
解决方案
在添加拦截器之前用@bean注解将拦截器注入工厂，接着添加拦截器

    @Bean
    public URLInterceptor urlInterceptor(){
        return new URLInterceptor();
    }

registry.addInterceptor里面是urlInterceptor()，不是之前的new URLInterceptor()

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