Error querying database. Cause: java.lang.NullPointerException
mybatis异常
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异常描述
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
Error querying database. Cause: java.lang.NullPointerExceptionThe error may exist in file [E:\IDEA\2022-6-1以前的文件\常用项目\GMALL\GMALL-product\target\classes\mapper\gmallproduct\SkuSaleAttrValueDao.xml]
The error may involve com.example.gmallproduct.dao.SkuSaleAttrValueDao.itemList
The error occurred while handling results
SQL: SELECT ssav.attr_id attr_id, ssav.attr_name attr_name, ssav.attr_value, group_concat( DISTINCT info.sku_id ) sku_ids FROM pms_sku_info info LEFT JOIN pms_sku_sale_attr_value ssav ON ssav.sku_id = info.sku_id WHERE info.spu_id = ? GROUP BY ssav.attr_id, ssav.attr_name, ssav.attr_value;
Cause: java.lang.NullPointerException
问题解决: 问题出在mapper文件的collection集合表述中 原来
<collection property="attrValues">
<result property="attrValue" column="attr_value" javaType="String" jdbcType="VARCHAR"/>
<result property="skuIds" column="sku_id" javaType="String" jdbcType="BIGINT"/>
</collection>
**改为**
<collection property="attrValues" ofType="com.example.gmallproduct.VO.item.AttrValueWithSkuIdVO">
<result property="attrValue" column="attr_value" javaType="String" jdbcType="VARCHAR"/>
<result property="skuIds" column="sku_id" javaType="String" jdbcType="BIGINT"/>
</collection>
也就是加上**oftype** **我的实体类**
@Data
@ToString
public class SkuItemSaleAttrVo {
private Long attrId;
private String attrName;
private List<AttrValueWithSkuIdVO> attrValues;
}
@Data
public class AttrValueWithSkuIdVO {
private String attrValue;
private String skuIds;
}
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