办法一：

给XXMapper.java加上Mapper注解，如：

import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface ArticleMapper extends BaseMapper<ArticleEntity> {
}

办法二：

给启动类加上MapperScan注解，如：

import org.mybatis.spring.annotation.MapperScan;

@SpringBootApplication
@MapperScan("com.example.**.mapper")
public class BlogApplication {
    public static void main(String[] args) {
        SpringApplication.run(BlogApplication.class, args);
    }
}