ibatis 中isNull, isNotNull与isEmpty, isNotEmpty区别

<spanstyle="font-family: Arial, Verdana, sans-serif; white-space: normal; "><strong>isNull, isNotNull与isEmpty, isNotEmpty区别</strong></span>

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

如下代码：

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<selectid="getCustomerRegNum"resultClass="int"parameterClass="QueryCustomerCondition">
         select count(cus_id) from cus_customer_tbl
<dynamicprepend="WHERE">
<isNotEmptyprepend="AND"property="cusWebFrom">
               ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
</isNotEmpty>
<isNotEmptyprepend="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），

[html]view plaincopy

<selectid="getCustomerRegNum"resultClass="int"parameterClass="QueryCustomerCondition">
         select count(cus_id) from cus_customer_tbl
<dynamicprepend="WHERE">
<isNotNullprepend="AND"property="cusWebFrom">
               ( CUS_CUSTOMER_TBL.CUS_WEB_FROM LIKE '%$cusWebFrom$%')
</isNotNull>
<isNotNullprepend="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 '%%')