初步解决了，但较奇怪的是，我是通过注释掉@Mapper，然后clean，再解开注释Mapper就可以了，这是什么原理哈?

老师，针对cource3这个mapstruct 一直生成这个代码，然后就是一直都是null，clean之后运行也还是这样，应该如何处理？

public class MetadataCopierImpl implements MetadataCopier {

    @Override
    public Metadata3 copy(DataCenterMetadata3 metadata) {
        if ( metadata == null ) {
            return null;
        }

        Metadata3 metadata3 = new Metadata3();

        return metadata3;
    }
}

Metadata3

@Slf4j
@Data
@NoArgsConstructor
public class Metadata3 implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * 指标规则主键id

     */
    private Long ruleId;
    /**
     * 指标英文标识
     */
    private String enName;

}

DataCenterMetadata3

@Data
@NoArgsConstructor
@Accessors(chain = true)
public class DataCenterMetadata3 implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * id
     */
    @TableId
	private Long id;
    /**
     * 指标规则主键id

     */
    private int ruleId;
    /**
     * 指标英文标识
     */
    private Integer enName;

}

MetadataCopier
目前遇到的问题就是需要是不是重新注释一下这个@Mapper，不然会报错

// 用输入输出类型自动判断
//@Mapper(uses = DateMapper.class)
public interface MetadataCopier {

//    @Mapping(source = "myDate", target = "myDate", dateFormat = "yyyyMMdd HH:mm:ss")
    @Mapping(source = "createTime", target = "createTime", dateFormat = "yyyy/MM/dd HH:mm:ss")
    @Mapping(source = "priceMax", target = "priceMax", numberFormat = "#.##E0")
    @Mapping(source = "price", target = "price", numberFormat = "$#.00")
    Metadata3 copy(DataCenterMetadata3 metadata);

    MetadataCopier INSTANCE = Mappers.getMapper(MetadataCopier.class);
}