ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别

在iBATIS中isNull用于判断参数是否为Null，isNotNull相反

isEmpty判断参数是否为Null或者空，满足其中一个条件则其true

isNotEmpty相反，当参数既不为Null也不为空是其为true

判断之后做相对应的表达式操作

<select id="getCustomerRegNum" resultClass="int" parameterClass="QueryCustomerCondition">
select count(cus_id) from cus_customer_tbl
<dynamic prepend="WHERE">
<isNotEmpty prepend="AND" property="cusWebFrom">
( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
</isNotEmpty>
<isNotEmpty prepend="AND" property="cusWebAgent">
( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')
</isNotEmpty>
</dynamic>
</select>

当之传入参数 cusWebForm 而不传入 cusWebAgent 时，产生的SQL语句为：

select count(cus_id) from cus_customer_tbl WHERE ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%')

而当XML代码用<isNotNull > 配置时（注意他们的区别），

<select id="getCustomerRegNum" resultClass="int" parameterClass="QueryCustomerCondition">
select count(cus_id) from cus_customer_tbl
<dynamic prepend="WHERE">
<isNotNull prepend="AND" property="cusWebFrom">
( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
</isNotNull>
<isNotNull prepend="AND" property="cusWebAgent">
( CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%$cusWebAgent$%')
</isNotNull>
</dynamic>
</select>

同样 ，当之传入参数 cusWebForm 而不传入 cusWebAgent 时，产生的SQL语句为：

select count(cus_id) from cus_customer_tbl WHERE ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%baidu%') AND (CUS_CUSTOMER_TBL.CUS_WEB_AGENT LIKE '%%')